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SOCIO-BIOLOGY

Know others,
that you might understand yourself. ~JKH

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. . See also: the sex file.

NEWS ITEMS

Very related news is in See the sex file.)

Oct 23, 06: [Here's why we have blue eyes!] Blue-eyed men prefer blue-eyed women, apparently because eye color can help reveal whether their partner has been faithful, researchers said. [and why babies take mostly after their fathers.]
. . "Before you request a paternity test, spend a few minutes looking at your child's eye color." Under the laws of genetics, two parents with blue eyes will always have blue-eyed children, it said. So a blue-eyed man can know his blue-eyed wife or partner has cheated on him if their child has brown eyes.
. . But brown-eyed men, who cannot find any clues about paternity from a child's eye color, had no preferences by eye color. Women showed no preference for brown- or blue-eyed men, irrespective of their own eye color. A quarter of children born to two brown-eyed parents who have both brown and blue-eye genes among their ancestors will have blue eyes. The rest will be brown.
. . In a second study, 443 young adults of both sexes were asked about the eye color of their partners -- blue-eyed men were also the group with the highest proportion of partners with the same eye color.

Oct 23, 06: Sucking up to win the support of the boss dates back to our furry ancestors. The motivation, for monkeys, is life and death. Rather than grabbing coffee for the CEO, monkeys have for eons picked dead skin and bugs from the fur of higher-ranking monkeys. They do it in exchange for backing in fights.
. . This resolves a historical question about primate grooming. Like other social animals, primates live in societies where individuals often come to blows over food or access to mates, as well as trying to climb the ladder to alpha-hood. When witnessing a conflict between two group-mates, a third party must choose which contestant to back.
. . Schino found this choice is at least partially determined by past grooming received from each mate, with frequent groomers receiving more frequent support from those served.
. . The study also showed this reciprocal altruism is generally more frequent in some primates than others. Old World monkeys, such as macaques and baboons found in Asia and Africa, practice groom-for-support behaviors more than New World monkeys such as capuchins and marmosets found in Mexico and Central and South America.

Oct 23, 06: The early bird might get the worm, but the last in line makes the baby. From bonobo chimpanzees to fruit flies, many female animals mate with multiple partners that often queue up for the event. Studies have shown that the the last male to mate with a female is the most successful at impregnating her. Nobody has understood why.
. . The last male can take advantage of a more "sperm-friendly" environment created by males that have copulated before him, according to a new model put forth by David Hosken and David Hodgson of the University of Exeter.
. . Males ejaculate hundreds of millions of sperm into the female reproductive tract, but most don't make it to the egg for fertilization. In mammals, just .001% of the ejaculated sperm hit the fertilization target.
. . The seminal fluid in a male's ejaculate helps to buffer the acidity, creating more viable conditions for sperm. By waiting in line, males could exploit the ejaculate from other males, giving their sperm a cushy ride into the female's uterus to fertilize eggs.
. . Going last also means the male could lower the amount of sperm in his ejaculate since there's a higher probability of that sperm being successful. Producing sperm is a costly investment and has been shown to require a good chunk of an animal's resting energy.
. . The finding seems to apply to any organism in which females mate with multiple partners in rapid succession, out in the open where others can watch. The mating needs to be relatively rapid for the physical effects of a prior male's sperm to remain. This includes females of many fruit-fly species, which re-mate within an hour. The male yellow dung fly will interrupt and take over a copulation, removing and replacing their rivals.

Oct 9, 06: Women dress to impress when they are at their most fertile, U.S. researchers said today in a study they say shows that signs of human ovulation may not be as mysterious as some scientists believe.
. . A study of young college women showed they frequently wore more fashionable or flashier clothing and jewelery when they were ovulating, as assessed by a panel of men and women looking at their photographs. "They tend to put on skirts instead of pants, show more skin and generally dress more fashionably."
. . Writing in the journal Hormones and Behavior, Haselton and colleagues said their findings disproved the conventional wisdom that women are unique among animals in concealing, even from themselves, when they are most fertile.
. . Some animals release powerful scents when ready to mate, while others display skin color changes, but human ovulation is notoriously difficult to detect. The team used a test to check fertility/ovulation in their study.
. . The women came back several times over the course of a month and were photographed twice --once in their fertile phase and another time in their least-fertile phase. The researchers asked 42 men and women, some older than the volunteers, to assess these photographs by asking, "In what photo is the person trying to look more attractive?" The judges chose the photograph taken during the women's fertile phases 60% of the time, Haselton said. "This is well beyond chance."
. . Haselton's team had earlier reported that women were more likely to flirt and look at attractive men when ovulating.

Aug 29, 06: Russia is to create its first women-only traffic police unit because commanders believe they are less corrupt than men, a newspaper reported.

Aug 24, 06: A spat with your lover can be trying. Humans have of course devised ways of making up, including tight hugs and the customary apology flowers. Killer whales have their own tricks for mending relations, a new study finds. Rather than a bouquet, however, they might opt for an intimate swim. After the mother chased the father for several minutes, each zipped away to separate aquatic quarters to cool off for about 10 minutes. Then, the mates smoothed over their clash with side-by-side swimming, called echelon swimming.
. . Studies have shown that chimpanzees kiss and hug after a dispute, and other primates such as bonobos resort to sexual activity to resolve conflicts. Until now, reconciliatory behavior had not been shown in any marine mammal.

Aug 6, 06: For male nightingales, the key to scoring with the ladies is to cut their opponents off. Male songbirds often compete for mates through singing contests. The dominant ones usually start singing before an opponent finishes his song, signaling aggression that female birds sometimes find attractive.
. . In a study of nightingales, scientists were interested to learn why 49% of the males didn't have a mate during breeding season.
. . Female nightingales see song overlapping in a potential mate as a sign of aggression, an indication of other beneficial qualities. These males might be in better health and thus able to defend a territory better than males in poor condition, Kunc explained. And because aggressive males are more likely to have a mate, they also have a higher rate of reproductive success.
. . The nightingale is one species where song overlapping might play an important role, but black-capped chickadees, great tits, little blue penguins, and domestic canaries might also use this mechanism, Kunc said. "Furthermore, this phenomenon does not only occur in birds", but also in crickets, frogs and toads.

July 31, 06: A male dog will whine and beg in deference to a stronger dog, but will lower its voice into a guttural growl if it thinks it has a fighting chance. Men unconsciously do a similar thing, scientists say.
. . A new study finds that the lower the pitch of a man's voice, the more physically dominant other men think he is. And men lower their voice pitch when addressing a man they believe to be less dominant than themselves, but raise it when speaking to someone they think is more dominant.
. . Vocal pitch, determined by the main frequencies in a voice, is about half as high in men as in women. This difference has traditionally been explained as a product of sexual selection, in which women favored men with lower-pitched voices.
. . One reason women might prefer men who speak in low voices is that vocal pitch is partly related to physical size. Taller men tend to have lower voices because they have longer vocal tracts and vocal folds, the main determinants of pitch. Vocal anatomy is also thought to signal a man's level of testosterone, a hormone linked to physical aggressiveness and prowess.
. . Studies have shown that women favor men with low, masculine voices during periods in their menstrual cycle when they're likely to get pregnant, and also that they prefer men with lower voices for short-term sexual flings.

July 14, 06: From an evolutionary perspective, making babies with a closely related family member is a cardinal sin. A new study suggests that like many animals, humans have evolved built-in mechanisms to help keep this from happening.
. . The study finds that the absence of a father, the presence of half- and step-brothers, and living in an urban environment are all associated with the earlier onset of a girl's first period, known as "menarche." Meanwhile, the presence of sisters in the household while growing up has the opposite effect.
. . The researchers speculate that the findings are part of an evolutionary strategy to prevent inbreeding and that it is regulated by chemical signals, called pheromones, that influence our behavior without our knowing it.
. . Menarche can occur anytime between age 8 and 16 bug usually around age 12. It signals the looming onset of fertility.
. . Inbreeding is breeding between close relatives. If practiced repeatedly within a population, it creates a situation in which the genes among individuals are overly similar—that is, the "genetic diversity" of the population is reduced. This is bad because the onset of a sudden threat, such as a deadly virus, can exploit a common weakness and wipe out an entire population. Inbred individuals are also more likely to have physical and health defects as well as lower levels of fertility.
. . Contrary to what was predicted, having a stepfather in the house was not associated with a delay of menarche. One possible explanation that comes from animal studies is that female sexual maturation speeds up in the presence of any unrelated male who is fertile.
. . Also surprising was the fact that the presence of half-brothers did not delay sexual maturation. If the goal is to prevent inbreeding, having sex with a half-sibling who shares 50% of your genes might also seem like a bad idea. However, Matchock speculates that half-brothers are "genetically different enough so as not to activate some of these anti-inbreeding strategies." Other research has also shown that people tend to pick mating partners who are like themselves but not too similar.
. . The finding that urban girls had earlier ages of menarche than girls who grew up in rural areas is consistent with past research, but the cause for the discrepancy is still unknown. One possibility is that city life provides more opportunities for social interactions outside the home and thus more opportunities for sex with members outside the immediate family.
. . Contrary to previous studies, neither the total number of siblings nor the numbers of brothers were associated with later onset of menarche. The presence of other sisters, and older sisters in particular, did delay menarche, however.

June 14, 06: Erotic images elicit faster and stronger electrical responses in a woman's brain than other images ranging from pleasant to disturbing.
. . The finding might not sound surprising, but researches did not expect responses to erotic images to emerge so quickly, apparently involving different circuits than the processing of other images. "We believed both pleasant and disturbing images would evoke a rapid response, but erotic scenes always elicited the strongest response."
. . The test involved 264 women who were shown 55 images of water skiers, snarling dogs, partially clad couples in sensual poses, and other scenes. Electrodes on the subjects' scalps measured brain activity.
. . The signals begin firing long before a subject was conscious of what she saw. Erotic images elicited neuron firing within 160 milliseconds --about 20% faster than occurred with any of the other pictures. The stimulation then branched out to different brain regions for erotic images compared to the others.
. . Previous research indicated men are more aroused by erotic images than women, so Anokhin and his colleagues expected women to respond with lower levels of brain activity compared to men. "But that was not the case", Anokhin said. "Women have responses as strong as those seen in men."
. . The next question on Anokhin's mind: Whether or not the human prefrontal cortex contains special neurons tuned for sex.

June 12, 06: Male canaries hone their songs to get girls, but their sexy tweets might do more than that. A new study reveals that female songbirds alter the size of their eggs, and possibly their chicks' sex, in response to hearing a sexy song from a male.
. . Researchers played an assortment of male canary songs—ranging from what birds consider sexy to less attractive—to female domesticated canaries. More attractive songs induced larger eggs.
. . In the wild, larger eggs are more likely to contain male chicks, but the researchers found no difference in brood sex ratio between the different songs played to the females. Since the sexy song generated a large egg but not male chicks, the researchers suggest mothers can influence their offspring's sex in more than one way.
. . Scientists have long known the power of a male canary's song. A good-sounding song tells females that its composer is healthy and has good genes, and males with attractive songs get more girls.

May 25, 06: Girls from broken homes may grow up to be less attractive, research published by the Royal Society shows. Two studies from a team at St Andrew's University suggested that women whose parents had separated or had a poor relationship looked more masculine.
. .The results may be linked to levels of testosterone - the male sex hormone. However, it is unclear if increased testosterone in the offspring of parents who separate is genetic or caused by stress of an unhappy family life.
. . Researchers assessed facial features and body shape in 229 women and found those from stable homes appeared more feminine and healthy. They took photographs of psychology students who had completed a questionnaire about their family background. The pictures were rated for attractiveness, feminity, and healthiness.
. . Women whose parents had a good relationship were found to be significantly more attractive than women whose parents had separated. Women whose parents had stayed together but had a poor relationship were rated the least attractive of the three groups and were also judged to be the least healthy.
. . In a second study of 87 of the same young women, researchers assessed body mass index, waist-hip ratio, and waist-chest ratio. Growing up with parents who had a poor relationship was associated with increased weight around the waist, producing a more masculine figure and an increased body mass index.
. . Previous research has shown that girls whose parents split up are more likely to start their periods earlier, start having sex sooner and have a higher rate of teenage pregnancy.

May 11, 06: Women live longer than men. And now scientists suggest a simple Darwinian reason: Competing for a mate can wear a guy out or get him killed. "Women live longer in almost every country, and the sex difference in lifespan has been recognized since at least the mid-18th century", said Daniel Kruger at the University of Michigan. "It isn't a recent trend; it originates from our deep evolutionary history."
. . In common chimpanzees, Kruger and his colleague Randolph Nesse report, mortality spikes among males around age 13, just as they're old enough to breed and start competing for social status. Males of many species must fight vigorously for the right to mate. Think of rams butting heads. Spectacular male bird plumage is another example of biological effort required to succeed, effort that uses energy and can shorten a life. In this scheme of natural selection, evolution shapes traits that help the best genes survive, sometimes to the detriment of individuals.
. . Human males don't always have to wrestle to get a woman these days, but the pressure to succeed sexually hasn't changed much, the researchers argue. Only the methods have been revised. To impress women, men remain prone to risky behavior, just as they have been for millennia and just as other male animals are.
. . Another study last year reached similar conclusions. It cited "excessive risk taking, aggression, and the suppression of emotions by boys and young men" as being directly related to lower life expectancy in men.
. . Among the not-so-beneficial behaviors this includes are smoking, reckless driving and violence, Kruger and Nesse write. This idea is reinforced by data that show low social status has a greater impact on male mortality rates than on those of women: Men of lower status or who lack a mate are more likely to engage in a riskier pattern of behaviors."

May 9, 06: Lesbians' brains react differently to sex hormones than those of heterosexual women, new research indicates. That's in line with an earlier study that had indicated gay men's brain responses were different from straight men --though the difference for men was more pronounced than has now been found in women.
. . Lesbians' brains reacted somewhat, though not completely, like those of heterosexual men, a team of Swedish researchers said in an edition of Proceedings of the National Academy of Sciences. A year ago, the same group reported findings for gay men that showed their brain response to hormones was similar to that of heterosexual women.
. . In both cases, the findings add weight to the idea that homosexuality has a physical basis and is not learned behavior. "It shows sexual orientation may very well have a different basis between men and women ... this is not just a mirror image situation", said Sandra Witelson, an expert on brain anatomy and sexual orientation.
. . The same team reported last year on a comparison of the response of male homosexuals to heterosexual men and women. They found that the brains of gay men reacted more like those of women than of straight men. The new study shows a similar, but weaker, relationship between the response of lesbians and straight men. All three groups rated the male hormone more familiar than the female one. Straight women found both hormones about equal in intensity, while lesbians and straight men found the male hormone more intense than the female one.
. . In heterosexual males, the male hormone was processed in the scent area, but the female hormone was processed in the hypothalamus, which is related to sexual stimulation. In straight women, the sexual area of the brain responded to the male hormone, while the female hormone was perceived by the scent area. In lesbians, both male and female hormones were processed the same, in the basic odor processing circuits.

May 9, 06: Women looking for a long-term relationship like men who like children --and they can tell which guys might be interested in becoming fathers just by looking at their faces. Those are among the findings of a study of college students in a British scientific journal. "The more they perceived the men as liking kids, the more likely they could see having a longer-term relationship." Experts said evolution has apparently programmed women to recognize men who might be interested in propagating the species by raising a family.
. . The study wasn't all bad news for men not interested in settling down. It found that women can look at men's faces and figure out which of them have the highest testosterone levels. Those men --rated the most masculine by the women-- turn out to be just the kind of guys they would want for a fling. [Women ALL do this, tho few are AWARE of it, & usually deny it.] "Women make very good use of any information they get from a man's face", said co-author Dario Maestripieri, an associate professor of comparative human development at the University of Chicago. "Depending on what they want and where they are in their lives, they use this information differently."
. . The women were asked to rate the men on four qualities: "likes children", "masculine", "physically attractive" and "kind." Then they were asked to rate how attractive they found each man for short-term and long-term romance.
. . The study found women did well at rating men on their interest in babies, and those they rated masculine generally had higher testosterone levels than the others. For example, the men who indicated they liked children the most were rated as above average in liking children by 20 of the 29 women. The men who showed no interest in children were correctly rated as below average in that category by 19 of the women.
. . The higher the women rated the men for masculinity, the higher they were rated as potential short-term romantic partners. The higher they rated men for their interest in children, the higher they were rated for long-term romance. The features that research has suggested denote high testosterone levels include a prominent jaw and a heavy beard.
. . The findings came as no surprise to those in the business of studying human behavior --and love. "What this study illustrates is that there are genetic programs that increase survival of the species because there are hormones in women that are cuing their reactions to the hormones of the men", said Dr. Daniel Alkon, scientific director of the Blanchette Rockefeller Neurosciences Institute.
. . Or as Kristin Kelly, a spokeswoman for the online dating service Match.com, put it: "They call it `love at first sight' for a reason. They don't say `love at first sentence', `love at first word'."
. . It is unclear just what about the men's faces tipped the women off about their interest in children.

Apr 21, 06: Scientists now have the first strong evidence that the emotional wiring of the sexes is fundamentally different. The brain seems to have evolved to be in tune with different stressors.
. . An almond-shaped cluster of neurons that processes experiences such as fear and aggression hooks up to contrasting brain functions in men and women at rest, the new research shows. For men, the cluster "talks with" brain regions that help them respond to sensors for what's going on outside the body, such as the visual cortex and an area that coordinates motor actions. [Any lions coming?]
. . For women, the cluster communicates with brain regions that help them respond to sensors inside the body, such as the insular cortex and hypothalamus. These areas tune in to and regulate women's hormones, heart rate, blood pressure, digestion and respiration. [How's the baby?]
. . The finding, published in the recent issue of the journal NeuroImage, could help researchers learn more about sex-related differences in anxiety, autism, depression, irritable bowel syndrome, phobias and post-traumatic stress disorder.
. . The new study focused on activity in the amygdala, a cluster of neurons found on both sides of the brain and involved for both sexes in hormone and other involuntary functions, as well as emotions and perception. Cahill already knew that the sexes use different sides of their brains to process and store long-term memories, based on his earlier work. He also has shown that a particular drug, Propranolol, can block memory differently in men and women.
. . The scans also showed that men's and women's amygdalas are polar opposites in terms of connections with other parts of the brain. In men, the right amygdala is more active and shows more connections with other brain regions. In women, the same is true of the left amygdala.
. . Scientists still have to find out if one's sex also affects the wiring of other regions of the brain. It could be that while men and women have basically the same hardware, it's the software instructions and how they are put to use that makes the sexes seem different.

Apr 15, 06: Scientists measured the size and fullness of lions' manes in northern and southern zoos and found that cats living in colder climates had heartier hairstyles, a key attractant to female lions.
. . Nutrition, social factors, and genetics have previously been considered important factors affecting mane quality, but the new finding suggests that up to one-half of the mane's length and density is determined by temperature. A thick mane retains heat in a hot, dry climate -—like wearing a fur hat or wool scarf -—and can cause a big cat to overheat.
. . Northern zoo lions, such as one from Illinois and a male from St. Louis, both have extremely sexy manes. Hair grows halfway down their backs, all over their front legs, and even on their bellies. Two southern lions, one from Houston and another from Tyler, Texas, both sport impressive manes, the judges say. But their hair looks thinner than the northern lions and they're hairless on the back and belly. The quality of a male's mane broadcasts information to both sexes. A large, thick mane tells the other guys to "stay away", and says "come hither" to the girls.
. . Unlike wild lions, captive lions don't have to fight for their food. After losing a fight, a wild lion feels less manly [lionly?] and his testosterone levels drop, which thins out his mane.

Mar 14, 06: The key ingredient to a woman's marital bliss is her husband's emotional commitment, suggests a new study based on a survey of 5,000 couples across the country. The finding is in contrast to previous research that focused on a husband's salary and division of household work as the main drivers of a woman's perception of a happy marriage.
. . Even so, the new research determined that women whose husbands bring home more than 68% of the bacon are the most content. "I was very surprised to find that even egalitarian-minded women are happier when their marriages are organized along more gendered lines."
. . Fairness is also considered an important element. Women who perceive that housework is shared in a fair manner consider themselves happier partners. Fair in this case does not necessarily mean splitting housework evenly—most of the women in this happier category perform the majority of household chores themselves. But because they believe that their husbands are playing an important role as providers, they view the unequal work split as fair.

Mar 11, 06: According to new research, the ability to dance may have been a factor in survival for our prehistoric ancestors, who used their moves to bond and communicate with each other when times were tough. The study suggests that, as a result, today's creative dancers actually share two specific genes. Both genes are associated with a predisposition for being good social communicators. Scientists believe this gave early humans who were well coordinated and rhythmic a distinct evolutionary advantage.
. . DNA was obtained from 85 elite dancers and their parents to compare with a group of people lacking any distinguishing characteristics, as well as a group of athletes. The genes studied don't control a specific physical ability, but they dictate two well-known social and behavioral chemicals in the body: serotonin and vasopressin.
. . As researchers suspected, both chemicals were found in much larger quantities among the dancers. In other words, while the elite dancers couldn't be put in a different physical category from everyone else, they all shared genes that made them more social.
. . In his new book "The Singing Neandertals: The Origins of Music, Language, Mind, and Body" (Harvard University Press, 2006), Mithen contends that because of their communication powers, dance and music likely became an important tool of social interaction as soon as humans could walk and talk.
. . "It has been argued that the specific nature of human anatomy suggests that it evolved for endurance running as much as walking. As such it could have also been used for dancing, as bipedalism requires high degrees of muscle control, balance and flexibility", he said. "In many societies today, dancing is used as a form of display for attracting mate", Mithen points out. "Dancing is a means to show off one's physical fitness and co-ordination, qualities that would have been useful for survival in prehistoric hunter-gatherer societies."

Mar 8, 06: Romance might be ruled as much by our DNA as our heads, let alone our hearts. A decade ago, the first clues to what we really see in a face came from Professor Dave Perrett's team at St Andrews, working with colleagues in Japan. Their study of female faces contradicted feminist ideas.
. . Female facial beauty transcends racial and national boundaries: a pretty face, whether Oriental or Western, was as attractive to Japanese as Britons. The age-old idea that beauty is in the eye of the beholder is a romantic myth. Prof Perrett's work suggested that our appreciation of beauty has a deep-seated biological explanation: the face of an intended Valentine gives a profound insight into whether our true love will efficiently pass our genes on to future generations.
. . From the cold-eyed perspective of Darwinian evolution, the mating game has a single purpose: to mix our genes with another person's to help ours survive and propagate - the more the better. We seek a partner with good looks because this is a biological advert that says good genes are to be found in this particular body to help our own genes thrive in the next generation.
. . In one experiment, 200 participants viewed human faces that had been digitally altered, for instance by giving them wide-spaced eyes. After a series of trials with Dr Lisa DeBruine at St Andrews and Dr Ben Jones in Aberdeen, he found that people are drawn to faces that are similar to those they know well. When the subjects were familiar with wide-eyed individuals, for example, they were less attracted to a novel face that had narrow-spaced eyes. "The brain connects familiarity with attraction", said Dr Little, whose work has also shown that there is similarity between our partners' traits and those of our parents: if your parents have blue eyes, you are more likely to have a partner with blue eyes.
. . Life with our parents might lead us to choose partners with similar genes. And at St Andrews, Dr DeBruine has shown that people also prefer faces that look like their own, although this attraction weakens when it comes to the opposite sex. "Evolutionary theory tells us that our human instinct is to promote our own genes and choosing a partner who looks like us helps us to do this", said Dr Little.
. . The good news is that this finding also suggests you can make yourself relatively more beautiful by living among those who share your looks. The bad, of course, is that if you are exposed to enough Hollywood stereotypes of the opposite sex, you will find yourself drawn to untypically beautiful people. "If you plastered your bedroom with posters of Tom Cruise, you may find he becomes increasingly attractive to you", said Dr Little.
. . in Liverpool, Dr Craig Roberts is investigating whether our choice of partner is influenced by the need to have a different set of genes that control immunity (called the major histocompatibility complex, MHC). Different MHCs fight different diseases, so it's important to have a mix. Although we like the look of similar faces, earlier work suggested we most like the smell of someone who has a different MHC. "We might be seeing mechanisms that drive us to mate with people with similar genes, by being attracted to similar faces, but stop us from mating with people who are too closely related, by avoiding those who smell similar."
. . Symmetry: lopsidedness is thought to reflect how development in the womb has been derailed by poor health, alcohol and tobacco use. In pioneering studies of the common Japanese scorpion fly, Prof Randy Thornhill of the University of New Mexico found that males with the most symmetrical wings won the most mates. In our own species, studies have shown that women partnered to men with symmetrical bodies have the most orgasms, and those with symmetrical breasts are more fertile than those less evenly endowed. A relatively small nose and chin, big eyes and full lips are baby-faced characteristics that men are also drawn to. Once again, these are adverts of genetic quality: these features show a woman has high oestrogen levels, linked with fertility.
. . Men find allure in a woman's clear complexion --a darkening of the face can reveal if she has conceived another man's child, and is burdened with raising another's genes. Men also prefer waists to be 60-80% the size of hips, an indicator, however crude, of health and fertility.
. . There are also more subtle effects in the mating game where there is a trade-off between having good genes and teaming up with someone who will help look after them. Overall, women like men with feminized faces, such as Leonardo DiCaprio, because that is associated with being a good parent. And while masculine faces, such as Clint Eastwood and Arnold Schwarzenegger, are linked with strength and dominance, they are thought to be cold, and less good at parenting.

Mar 2, 06: Scientists have long wondered why organisms bother with sexual reproduction. It makes a whole lot more sense to just have a bunch of females that can clone themselves, which is how asexual reproduction works. Turns out sex might have evolved as a way to concentrate lots of harmful mutations into individual organisms so they could be easily weeded out by natural selection, a new computer model suggests.
. . The classic explanation for the onset of whoopee, about 1 billion years ago, is that it provides a way for organisms to swap and shuffle genes and to create offspring with new gene combinations that might survive if the environment suddenly changes. But some scientists think this isn't enough of a justification to outweigh the many costs of getting together to make little ones. Just ask any single person -—sexual organisms have to spend valuable time and resources finding and attracting mates.
. . If all organisms were like starfishes and cacti, which just drop pieces of themselves when they want to multiply, reproduction would be a whole lot simpler. There would be no need for elaborate peacock feathers or bird songs; stags wouldn't need antlers; elephant bulls wouldn't have to produce stinky cologne and guys probably wouldn't spend so much money on dates.
. . The new work could help test a hypothesis first proposed nearly 20 years ago, stating that sex evolved as a way to purge harmful mutations from a population. According to this view, the random shuffling of genes through sex will sometimes have the effect of concentrating many harmful mutations into single individuals. These individuals will be less healthy than their peers, and therefore more likely to be weeded out by natural selection, the thinking goes.
. . This hypothesis, called the "mutational deterministic hypothesis", is controversial though, because it assumes that single mutations by themselves are only slightly harmful, while a combination of many mutations together is much more damaging. Scientists call this phenomenon "negative epistasis". If negative epistasis were true, it would provide a powerful explanation for why sex has managed to persist for so long despite its numerous costs. But the phenomenon has yet to be widely demonstrated in nature and scientists have yet to figure out how such a thing evolved in the first place.
. . A new computer model by Ricardo Azevedo of the University of Houston and colleagues provides a possible answer to this last question. According to their model, negative epistasis is a natural byproduct of sex itself. The researchers created digital organisms that reproduced through sex in the same manner as real organisms. And like a regular organism, the virtual one developed a natural buffer to resist change by mutations. This ability, called "genetic robustness", is thought to be one of the main benefits of sex.
. . By shuffling genes, sex allows a population to spread its mutations across many individuals within a group. The mutations become diluted and can be effectively dealt with by an individual's genetic repair system. But the researchers found that the protection only works when the digital organisms were facing a few mutations at a time. When assaulted by many at once, their repair systems became overwhelmed and the organisms died. Azevedo think this happens in real life, too. "Most organisms are never forced to adapt to being resistant to many mutations at once. They're adapting to being resistant to one or maybe two mutations, but not to ten at the same time."
. . The researchers think that the combination of genetic robustness through sex and the limited ability of organisms to deal with mutations leads to the natural development of negative epistasis. "Most mutations are actually harmful, so anything that helps populations get rid of their harmful mutations is going to be important", Azevedo said. "The more interesting side of evolution is all the beneficial mutations that leads to complex structures, but the dirty work of evolution is to get rid of bad mutations, and that's where sex seems to play a role."

Feb 24, 06: The arrangement of a mother's genes could affect the sexual orientation of her son, according to a new study. The researchers examined a phenomenon called "X chromosome inactivation" in 97 mothers of gay sons and 103 mothers whose sons were not gay.
. . Chromosomes are large thread-like molecules that contain an organism's genetic instructions. Humans have 23 chromosomes. The X chromosome is one of two sex chromosomes in mammals; the other is the Y chromosome. Females have two X chromosomes and no Y's, while males have one X and one Y. Even though women have two X chromosomes, only one is functional because the other is inactivated through a process called "methylation." If one of the females' X chromosomes is not turned off, then there is too much genetic material, which can lead to a harmful overabundance of proteins. Down syndrome, for example, results from the presence of an extra copy of chromosome 21.
. . Normally, X chromosome inactivation occurs at random: half of the cells in a woman's body will have one X chromosome inactivated, while the other half inactivates the other chromosome. However, when the researchers in the current study examined cells from those women who had at least two gay sons -—42 mothers in total, or 23%—- they found something different. "Every single cell that we looked at in these women inactivated the same X chromosome." In contrast, only 4% of mothers with no gay sons and 13% of those with just one gay son showed this type of extreme skewing. Bocklandt thinks this suggests that a mother's X chromosomes partly influences whether her son is gay or not. "We think that there are one or more genes on the X chromosome that have an effect on the sexual orientation of the sons of these mothers, as well as an effect on the cells we were looking at", Bocklandt said.
. . Bocklandt was also involved in an earlier study that looked at the entire human genome of men who had two or more gay brothers. The researchers found identical stretches of DNA on three chromosomes—7, 8 and 10—that were shared by about 60% of the gay brothers in the study. That study also found mothers to have an unusually large role in their son's sexual orientation: the region on chromosome 10 correlated with homosexuality only if it was inherited from the mother.
. . The results from these two studies suggest that there are multiple genetic factors involved in determining a person's sexual orientation and that it might vary depending on the person. Most researchers now think that there is no single gay gene that controls whether a person is homosexual or not. Rather, it's the influence of multiple genes, combined with environmental influences, which ultimately determine whether a person is gay.
. . "I think if there's ever a time when we can make these changes for sexual orientation, then we will also be able to do it for intelligence or musical skills or certain physical characteristics -—but whether or not these things are allowed to happen is something that society as a whole has to decide. It's not a scientific question."

Feb 15, 06: To figure out how we pick mates, scientists have measured every shape and angle of the human face, studied the symmetry of dancers, crafted formulas from the measurements of Playboy models, and had both men and women rank attractiveness based on smelling armpit sweat. After all this and more, the rules of attraction for the human species are still not clearly understood. How it all factors into true love is even more mysterious.
. . But a short list of scientific rules for the game of love is emerging. Some are as clearly defined as the prominent, feminine eyes of a supermodel or the desirable hips of a well-built man. Other rules work at the subconscious level, motivating us to action for evolutionary reasons that are tucked inside clouds of infatuation.
. . In the end, lasting love depends at least as much on behavior as biology. But the first moves are made before you're even born. Starting at conception, the human body develops by neatly splitting cells. If every division were to go perfectly, the result would be a baby whose left and right sides are mirror images. But nature doesn't work that way. Genetic mutations and environmental pressures skew symmetry, and the results have lifelong implications.
. . Good symmetry shows that an individual has the genetic goods to survive development, is healthy, and is a good and fertile choice for mating. "It makes sense to use symmetry variation in mate choice", said evolutionary biologist Randy Thornhill of the U of New Mexico. "If you choose a perfectly symmetrical partner and reproduce with them, your offspring will have a better chance of being symmetric and able to deal with perturbations."
. . Thornhill has been studying symmetry for 15 years and scanned faces and bodies into computers to determine symmetry ratios. Both men and women rated symmetrical members of the opposite sex as more attractive and in better health than their less symmetrical counterparts. The differences can be just a few percent -—perceivable, though not necessarily noticeable.
. . By questioning the study participants, Thornhill also found that men with higher degrees of symmetry enjoy more sexual partners than men of lower symmetry. "Women's sex-partner numbers are dependent on things other than attractiveness. Because of the way that the sexual system in humans works, women are choosey. They are being sexually competed for. They have to be wooed and all that."
. . Body shape is of course important, too. And scientists have some numbers to prove it. Psychologist Devendra Singh of the U of Texas studied people's waist-to-hip ratio (WHR). Women with a WHR of 0.7—indicating hips significantly narrower than the waist—are most desirable to men. And an analysis of hourglass figures of Playboy models and Miss America contestants showed that the majority of these women boast a WHR of 0.7 or lower. In general, a range of 0.67 to 1.18 in females is attractive to men, while a 0.8 to 1.0 WHR in men is attractive to women, although having broad shoulders is more of a turn-on.
. . What exactly is encoded in the hip ratio? A big fat clue to whether the person will have enough energy to care for offspring. Where fat is deposited on the body is determined by sex hormones; testosterone in men and estrogen in women. If a woman produces the proper amount and mixture of estrogen, then her WHR will naturally fall into the desired range. The same goes for a male's testosterone. People in the ideal hip-ratio range, regardless of weight, are less susceptible to disease such as cardiovascular disorders, cancer, and diabetes, studies have shown. Women in this range also have less difficulty conceiving.
. . . The structure of a person's face also gives insight to fertility. Estrogen caps bone growth in a woman's lower face and chin, making them relatively small and short, as well as the brow, allowing for her eyes to appear prominent, Thornhill explained. Men's faces are shaped by testosterone, which helps develop a larger lower face and jaw and a prominent brow. Men and women possessing these traits are seen as attractive, Thornhill said, because they advertise reproductive health. Thornhill also points to the booming nip-‘n'-tuck business -—which is very much about improving a person's symmetry—- as evidence that people find the quality attractive. Another recent study revealed that symmetrical dancers are seen as more attractive.
. . Research reported last month found women both smell and look more attractive to men at certain times of the month. And symmetrical men smell better. Borrowing sweaty undershirts from a variety of men, Thornhill offered the shirts to the noses of women, asking for their impressions of the scents. Hands down, the women found the scent of a symmetrical man to be more attractive and desirable, especially if the woman was menstruating.
. . You might wonder how much of this we're consciously aware of. The rules of attraction, it turns out, seem sometimes to play out in our subconscious. In some cases, women in the study reported not smelling anything on a shirt, yet still said they were attracted to it. "We think the detection of these types of scent is way outside consciousness", Thornhill said. A 2002 study found women prefer the scent of men with genes somewhat similar to their own over the scent of nearly genetically identical or totally dissimilar men.
. . These subconscious scents might be related to pheromones, chemical signals produced by the body to communicate reproductive quality. The human genome contains more than 1,000 olfactory genes—compared to approximately 300 genes for photoreceptors in the eyes—so pheromones have received a lot of attention from basic research scientists as well as perfume manufacturers.
. . But the role of pheromones in the human realm remains controversial. Pheromones clearly act as sexual attractants in the animal world. Older male elephants, for example, exude sexual prowess with a mix of chemicals the younger bulls can't muster. Milos Novotny of the Institute of Pheromone Research at Indiana U has shown that special molecules produced by male mice can simultaneously attract females and repel, and even anger, rival males. Other studies have found similar responses throughout the animal kingdom.
. . Yet, many researchers are not sold on the idea that these odorless compounds play a role in human attraction. Count evolutionary biologist Jianzhi Zhang of the U of Michigan among the skeptical. In 2003, Zhang showed that a gene mutated 23 million years ago among primates in Africa and Asia that are considered to be human ancestors, allowing them to see color. This let the males notice that a female's bottom turned bright red when she was ready to mate. "With the development of a sexual color scheme, you don't need the pheromone sensitivity to sense whether a female monkey is ready to mate", Zhang said. "It's advantageous to use visual cues rather than pheromones because they can be seen from a distance."
. . A study last year suggested that human pheromones affect the sexual area of the brains of women and gay men in a similar manner.
. . Pheromones, like other scents, hitch a ride through the air on other particles, such as water droplets. They generally hover just 10 inches off the ground, however. So odds are slim they'll waft up to a human nose and fuel sudden passion at a nightclub. Watch any construction worker whistling at a passing woman from half a block away, and you can see how visual cues can be more powerful. And while they enter the nose like other scents, that's where the comparison stops. A pheromone's destination is a special organ called the volmeronasal organ, which humans now lack. From here the sexy scent travels along a neural pathway to the brain separate from other scents.
. . After our ancestors began to see color, a gene important in the pheromone-signaling pathway suffered a deleterious mutation, making it impossible for the scent signals to reach the brain, Zhang said. Imagine a train, leaving from Los Angeles to New York, discovers that the tracks in St. Louis are destroyed.
. . Although the classical pheromone pathway in both Old World primates and humans is dysfunctional, the mechanism for producing pheromones still works. Some scientists believe human pheromones might be influencing our decisions along the normal olfactory pathway.
. . The rules of attraction might drive our initial decisions, for better or worse. But lasting relationships are about much more than what we see and smell. Behavior plays a key role, with biology an intriguing contributing factor. One of the oldest theories about attraction is that like begets like. It explains that eerie perception that married couples sometimes look awfully similar.
. . Last year, J. Philippe Rushton, a psychologist at the U of Western Ontario, looked into the relationships of people's genes. Based on a set of heritable personality traits, having similar genetics plays 34% of the role in friendship and mate selection, he found. "The main theory is that some genes work well in combination with each other. If these genes evolved to work in combination, then you don't want to break that up too much for your offspring. Finding a mate with similar genes will help you ensure this." If your spouse is genetically similar, you're more likely to have a happy marriage, for example. Child abuse rates are lower when similarity is high, and you'll also be more altruistic and willing to sacrifice more for someone who is more genetically like you, research shows.
. . It probably comes as little surprise that people are drawn to individuals with similar attitudes and values, as psychologist Eva Klohnen at the U of Iowa found in a 2005 study of newlywed couples. These characteristics are highly visible and accessible to others and can play a role in initial attraction. When it comes to sticking together for the long haul, researchers have shown that likeness of personality, which can take more time to realize, means more.
. . Comedy can also help a relationship. But the importance of humor is different for men and women, says Eric Bressler of McMaster U. A woman is attracted to a man who makes her laugh, Bressler found in a 2005 study. A man likes a woman who laughs at his jokes. Somewhere amid attraction and sex, we all hope, are strong feelings of love. But which of all the motivations really drives us? Interestingly, brain scans in people who'd recently fallen in love reveal more activity related to love than sex. "Romantic love is one of the most powerful of all human experiences", says Helen Fisher, an anthropologist at Rutgers U. "It is definitely more powerful than the sex drive."
. . The rules of attraction make up a pretty long list. No scientist knows the order of the list. But near the top is perhaps one of the toughest characteristics to gauge in advance in the search for the perfect partner. Despite all their differences, men and women place high value on one trait: fidelity.
. . Cornell U's Stephen Emlen and colleagues asked nearly 1,000 people age 18 to 24 to rank several attributes, including physical attractiveness, health, social status, ambition, and faithfulness, on a desirability scale. People who rated themselves favorably as long-term partners were more particular about the attributes of potential mates. After fidelity, the most important attributes were physical appearance, family commitment, and wealth and status. "Good parenting, devotion, and sexual fidelity—that's what people say they're looking for in a long-term relationship", Emlen says.

Feb 9, 06: Altruism may breed better marriages, a new study suggests. Or, the data might mean that good marriages make people more altruistic. "Altruistic love was associated with greater happiness in general and especially with more marital happiness."
. . Study participants were asked whether they agreed with statements that define altruism, such as, "I'd rather suffer myself than let the one I love suffer", and "I'm willing to sacrifice my own wishes to let the one I love achieve his or hers." Those who agreed with the statements tended to also report happiness with their spouses. Among the more altruistic, 67% rated their own marriage as "very happy." Among those who were profiled as the least altruistic, only 50% said they were very happy in marriage.
. . And here's one for those of you who're still waiting for your partner to commit: 40% of the married people ranked near the top for altruistic responses, while only 20% of those who had never married did so. The divorced and separated came in at around 25%.
. . The study asked dozens of questions to gauge both altruistic intentions and behaviors. How often do you give blood? Do you return money when a cashier makes a mistake in your favor?
. . In a separate finding, Smith looked at a similar study from 2002 and found that altruistic feelings are on the rise. The number of people having "tender, concerned feelings toward the less fortunate" rose 5%, to 75%.
. . Smith also analyzed empathy, described as feeling protective of others or concerned for the less fortunate. Some of the findings: * Women have a greater feeling of empathy than men.
. . * Children from two-parent homes are more empathetic.
. . * Girls raised by a single father are the least likely to develop empathy.
. . * Financial status bears little on altruism or empathy.
. . * People who vote are more empathetic and altruistic.
. . * Empathy is higher among those who fear crime.
. . * Empathy is higher among those who support increased spending on social programs.

Feb 1, 06: It's long been thought that singing is used by whales to attract mates or repel rivals, but new Australian research indicates the serenades may be the basis on which the females select their sexual partners. University of Queensland researchers said that they believe the male's songs are part of an elaborate courtship ritual between humpback whales as they appear to be directed more towards females than to warn off rival males.
. . While he cannot say the songs attract the females, they do facilitate sex. "Certainly there's evidence for courtship. It seems to certainly be a courtship display that facilitates mating interactions with females." He said the songs, made up of chirps, moans and barks, were repetitive but structured and could be detected as far as 20 km away. "The singing can last as long as 10, 15, 20 minutes to as long as 23 hours --on average, we are looking at three hours."

Jan 26, 06: New research reveals that monkey cops help keep social groups in line. Not having guns or nightsticks, they leverage their group seniority, craft intimidating reputations and count on good voter turnout.
. . Take the primate police out of a group, as researchers did, and the rest get more violent and aggressive. Interaction between cliques drops significantly. "It's not just that violence goes up, but a whole range of behavior involving a whole range of individuals suddenly disappears."
. . Pigtailed macaque monkeys, Macaca nemestrina, don't just pull into town like Wyatt Earp or Dirty Harry and take over. They have to be "appointed" to the position. Instead of a paper ballot, inferior monkeys bare their teeth to a more dominant member of the group. When an individual receives these voting signals from most of the group, it shows he is well respected—or feared—and he becomes the new sheriff in town. In general, the larger and more senior monkeys are voted into the policing role. But having a gang to back you up counts for something, too. A single Schwarzenegger-like monkey may not receive as many "votes" from the group as a smaller individual with several brothers.
. . Once elected, police monkeys earn certain rights and responsibilities, one of which is to peacefully settle conflicts. They usually do this by stepping between combatants or chasing bad monkeys away.
. . When Krakauer and his colleagues removed the police force -—which in this case consisted of three males, but can also include females—- they saw a drastic change in a once peaceful, interactive society. The creatures split into cliques, mostly based on tight family relationships or friendships, and then interacted poorly. "The policers are indirectly providing the security needed for complex forms of social interaction to take place", Krakauer said. "The monkeys are afraid of approaching each other if the policers are not there to resolve a potential conflict."

Jan 26, 06: Promiscuity is not a trait most people regard in high esteem, but for some animals it may be the key to increased reproductive success. In much of the animal world, sleeping around increases the likelihood of healthy offspring and reduces the chance of spontaneous abortion of an entire brood.
. . Also, evidence suggests that in a womb filled with half-brothers and half-sisters, offspring sired by multiple strangers may help those fathered by their mother's brother make it out alive. Since all these developmental processes go on at the cellular level inside the female reproductive tract of live-bearing species, these effects have proven difficult to monitor.
. . So researchers studied the promiscuous habits of pseudoscorpions, which are small venomless arachnids that look like scorpions with no tails and carry their developing young in external wombs on their backs -—a convenient setup for scientists.
. . Females that mate with multiple, unrelated males at one time produce more, and healthier, offspring, the study found. Females mating with a two of their brothers suffered the highest miscarriage rate, nearly 40%. Mating with a brother and an unrelated male, or the same non-brother twice, both produced abortion rates around 20%. Pairings considered promiscuous, with two non-brother males, resulted in a miscarriage rate less than 10%. Dual non-brother pairings also resulted in a higher number of viable offspring per brood -—about 65—- compared to about 50 for brother/non-brother pairings and just 40 for pairings with two brothers.
. . Biology seems to have a thing against inbreeding. Besides being gross from a human perspective, inbreeding increases the risk of inheriting identical copies of genes detrimental to the health of the offspring. For example, rampant inbreeding in some European royal families resulted in a high rate of hemophilia in later generations.
. . Additionally, genetic similarity of embryos to their mother can set off immune system reactions that damage developing offspring. And inbred offspring generally don't receive proper nutrition from their mother while in the womb. These complications play an important role in triggering spontaneous abortion.
. . The greater success of brother/non-brother pairings compared to brother/brother couplings suggests that out-bred offspring (those sired by fathers not related to the mother) somehow rescue their inbred half-siblings while both sets are still in the womb.

Jan 25, 06: Women enjoy free time less than men, a new study finds. [not "less free time"...] And it's getting worse. When men have free time, they feel less rushed than when their schedules are packed. Women relieved of work do not feel less rushed, however. The results suggest that mothers in particular feel the pressures of children and housework even when they have time to kick back.

Jan 24, 06: [this is central to socio-bio...] For some male bats, sexual prowess comes with a price — smaller brains. A research team led by Syracuse University biologist Scott Pitnick found that in bat species where the females are promiscuous, the males boasting the largest testicles also had the smallest brains. Conversely, where the females were faithful, the males had smaller testes and larger brains. The study offers evidence that males —-at least in some species-— make an evolutionary trade-off between intelligence and sexual prowess. "Bats invest an enormous amount in testis, and the investment has to come from somewhere. There are no free lunches."
. . Bats are the second largest group of mammals (behind rodents) with about 1,000 known species. Pitnick's team looked at 334 species of bats and found a convincing contrast in testes size. In species with monogamous females, males had testes starting at 0.11% of their body weight and ranging up to 1.4%. But in species where the females had a large number of mates, Pitnick found testes ranged from 0.6% to 8.5% of the males' mass. "If female bats mate with more than one male, a sperm competition begins", Pitnick said. "The male who ejaculates the greatest number of sperm wins the game, and hence many bats have evolved outrageously big testes."
. . Promiscuity is known to make a difference in testicle size in some other mammals. For example, chimpanzees are promiscuous and have testicles that are many times larger than those of gorillas, in which a single dominant male has exclusive access to a harem of females.
. . Large brains, meanwhile, are metabolically costly to develop and maintain. Pitnick's research suggested that in those bat species with promiscuous females, the male's body used more of its energy to enhance the testes —-giving it the greater adaptive advantage-— and lacked the energy it needed to further develop the brain. The study found that in more monogamous species, the average male brain size was about 2.6% of body weight, while in promiscuous species, the average size dipped to 1.9%. [in bats, the weight is critical to flight, as well.]

Jan 23, 06: British homosexual men on average earn nearly 10,000 pounds (17,800 dollars) more per year than the male population at large, according to a study. Gay men working full time earn on average 34,200 pounds per year, compared with the national average for men of 24,800 pounds, according to a survey of 1,118 readers of Diva and Gay Times. Lesbians, meanwhile, earn on average 6,000 pounds more than the national average for women.
. . Last year's government figures, which put the number of gay people in Britain at more than three million -- or 6% of the population -- has allowed companies to make clearer estimates of the potential of the pink pound and led to huge interest among some of Britain's biggest brands, the Guardian said. The study found that gay people spent about three billion pounds on holidays in 2005, forked out another 1.9 billion pounds on clothing, and paid a total of one billion pounds in bills for portable telephones.

Jan 20, 06: Schadenfreude --getting pleasure from someone else's misfortune... and men seem to enjoy it more than women. Such is the conclusion reached by scientists at University College London in what they say is the first neuroscientific evidence of schadenfreude.
. . Using brain-imaging techniques, they compared how men and women reacted when watching other people suffer pain. If the sufferer was someone they liked, areas of the brain linked to empathy and pain were activated in both sexes.
. . Women had a similar response if they disliked the person experiencing the pain but men showed a surge in the reward areas of the brain. "The women had a diminished empathic response", said Dr Klaas Enoo Stephan, a co-author of the report. "But it was still there, whereas in the men it was completely absent."
. . The scientists, who reported their findings in the journal Nature, said the research shows that empathic responses in men are shaped by the perceived fairness of others.

Jan 20, 06: The scent of a woman is more attractive at certain times of the month, suggests a new study that had men sniffing women's armpit odor. "We were interested whether armpit odor changes across menstrual cycle", said study author Jan Havlieek of the Department of Anthropology at Charles University, Prague. "To test this, we asked a group of women to wear cotton pads in their armpits for 24 hours." The most attractive smells, men said, were from the time between the first day of menstruation and ovulation.
. . The typically 28-day menstrual cycle involves the physiological changes that occur in a woman to prepare for a possibility of pregnancy. It is controlled by the reproductive hormone system. A cycle is divided into four parts and starts on the first day of menstruation, which is the shedding of tissue and blood from the womb. In the follicular phase, a dominant ovarian follicle—which is a sack that contains the ova, or egg—grows, becoming ready to ovulate. The mature egg is then released in the phase known as ovulation around day 12. The cycle ends with the fertile phase.
. . Although many men would tell you they're always in the mood, Havlieek and colleagues discovered that men find odors during the follicular phase the most attractive and least intense. On the other hand, the highest intensity smells, corresponding to the lowest attractiveness for men, were found during the time of menstrual bleeding. Finally, the attractiveness of women's faces also changes during the month.
. . Havlieek's team found that facial images of women in the follicular phase -—when the dominant ovarian follicle is getting ready to ovulate—- are considered more attractive as compared to images taken in the luteal or fertile phase of the cycle.

Jan 20, 06: Staying married has its benefits, especially financial, as a new U.S.-wide study shows the wealth of a married person is almost double that of somebody who is single. Divorce among U.S. baby boomers reduced personal wealth by about 77% compared to that of a single person, while the financial standing among those who remained married almost doubled, according to a nationwide study.
. . Married people will see an increase in wealth that is more than just adding the assets of two single people, according to the study that was published in the Journal of Sociology.
. . Those who remained together saw a 93% gain in wealth compared to that of a single person, while individuals facing divorce saw their financial situation deteriorate long before the decree became final
. . For people who married and then divorced, there was a slow build-up of wealth during the early years of marriage and then a steady decline about four years prior to divorce.
. . The study also cast doubt on a common assumption that divorce is much harder financially on women than on men. In fact, it showed that women suffered financially only slightly more than men.

Aug 15, 05: Researchers at Oregon State University have announced another finding linking sexual orientation to biology, as opposed to learned behavior. The scientists recently discovered biological differences between the brains of homosexual rams and heterosexual ones.
. . The project began in 1995, when researchers at the federal Sheep Experiment Station in Dubois, Idaho, noticed that some rams would not mate with ewes, preferring rams instead. Wanting to ensure breeders could purchase heterosexual rams, researchers began a study in the hopes of determining the animal's sexual orientation. They received grants from the National Institutes of Health.
. . Fred Stormshak, distinguished professor of animal science at Oregon State, and one of the researchers in the project, said that his team found striking differences in the brains and hormones of certain rams. "The anterior preoptic area of the hypothalamus was about half the size of this part of the brain in heterosexual rams", he explained. Stormshak also noted that aromatase, an enzyme that converts testosterone into estrogen, was much lower in the homosexual rams. "What we're showing is what Simon Levay showed in human beings", Stormshak said, referring to the researcher who found a certain part of the homosexual hypothalamus was smaller than its heterosexual counterpart.
. . By birth, a person's orientation is already set. There's nothing you can do about it",Stormshak said. "That's what our evidence would suggest, but whether that's the case with humans, I'm not sure. The human is a much more complex organism than a ram. We're telling you there is a similarity, but we're not saying that is the sole difference between heterosexual and homosexual behavior."

Aug 11, 05: There are two methods of sex selection being used in the United States today. One is sperm separation –-the concept being that sperm with an X chromosome (for girls) weigh a little more than sperm with a Y chromosome (for boys). Because of this slight difference, the sperm can be sorted out and prepared for a simple insemination procedure. Sex selection by sperm separation has a success rate of about 90% for girls and about 70% for boys.
. . The other common method is pre-implantation genetic diagnosis, or PGD, which is a form of in vitro fertilization, where embryos are prepared in a test tube before implantation in a woman’s uterus. Unlike traditional in vitro fertilization, doctors take a few cells from each prepared PGD embryo to determine its sex, and they only implant embryos of the desired sexes. This method has a success rate of nearly 100%, but is more expensive and much more physically intrusive for a woman compared to sperm separation, researchers say. Neither method will cause any harm to the developing baby, they say.
. . Sex selection for non-medical reasons is banned in the United Kingdom – a decision that was favored by 80% of the population – but there are currently no laws to stop American parents-to-be from employing the technology.
. . Of the 561 women who participated in the study, 229 said they would like to choose the sex of a future child. Among these 229 there was no greater for demand for boys or girls. However, the data showed that women who already had one or more children of one sex would prefer for their next child to be of the opposite sex to create gender balance within the family.

Aug 10, 05: One in 25 fathers could unknowingly be raising another man's child, British scientists said. Researchers at Liverpool's John Moores University examined the findings of dozens of studies, published over the past 54 years, on cases of paternal discrepancy --where a man is proved not to be the biological father of "his" child. The findings of the studies varied dramatically --some concluded that only one man in 100 is not the father of his child while others put the figure as high as 30%. The Liverpool researchers calculated the median figure at around 4%.
. . "The importance lies not so much in the figure itself but in the implications, given that as a society we are increasingly making our decisions on the basis of genetics. If, for example, someone knows that their father had a history of hereditary heart disease, they might be tempted to alter their own diet."
. . In Britain, 20% of women in marriages or long-term relationships have had affairs, adding that the figures for other developed countries was similar. Around a third of pregnancies in Britain are unplanned, increasing the risk of paternal discrepancy.

Aug 7, 05: Men who are accused of never listening by women now have an excuse --women's voices are more difficult for men to listen to than other men's, a report said. Researchers at Sheffield university in northern England discovered startling differences in the way the brain responds to male and female sounds. Men deciphered female voices using the auditory part of the brain that processes music, while male voices engaged a simpler mechanism, it said.
. . "The female voice is actually more complex than the male voice, due to differences in the size and shape of the vocal cords and larynx between men and women, and also due to women having greater natural 'melody' in their voices. "This causes a more complex range of sound frequencies than in a male voice."
. . The findings may help explain why people suffering hallucinations usually hear male voices, the report added, as the brain may find it much harder to conjure up a false female voice accurately than a false male voice.

Aug 5, 05: [What does this suggest for single humans?] Californian fiddler crab females might be the choosiest mates in the world. Uca crenulata females will routinely check out 100 or more males before finally picking a mate. Apparently, in the world of fiddler crabs, size does matter, both in terms of the male himself and his abode. "The size of a male's burrow affects the development time of his larvae. A burrow of just the right size allows larvae to hatch at the safest time, the peak outward night time flow of the bi-weekly tidal cycle. Most animals sample just a few mates, presumably because search costs override the benefits of lengthy searches."
. . The average fiddler female, however, will inspect about 23 potential suitors and their bachelor pads before selecting a lucky winner. One especially hard to please female visited 106 male burrows, fully entering 15 of them, during her one hour and six minute search. Male fiddler crabs attract suitors by standing in front of their burrows and waving their enlarged claws, in a motion reminiscent of a human "come hither".
. . Dr deRivera also found that the largest females were the least picky, primarily because they could not fit into most of the burrows they visited. Therefore they were forced to choose one of the limited number of males with "super-size" burrows.

July 26, 05: Forget expensive presents or costly jewelry. Wining and dining is the best way for men to woo women, scientists said. Their results show that offering an expensive present signals the man's serious intentions but he must be wary of being exploited by gold-diggers who will dump him after receiving the gift.
. . "Guys are less likely to offer expensive gifts to females they don't have a long-term interest in. And girls won't be impressed with cheap gifts. By offering expensive but worthless gifts, such as dinner and theater trips, the male pays no cost if the invitation isn't accepted."
. . The researchers said giving gifts was a feature of courtship in humans and other species to impress females. Physical attraction is an important element but offering gifts also helps. "Our analysis shows there is evolutionary logic in men 'burning money' to impress the girl", said Professor Robert Seymour of UCL's department of mathematics. [It's the same in most species of mamal...]

July 19, 05: Both the U.S. marriage and divorce rates are dropping while the number of unwed couples living together is rising, according to an annual study of marriage.
. . The number of unmarried couples living together in the United States grew to more than 5 million last year. More than half of all first U.S. marriages are preceded by living together, it said. The study did not specify whether it meant first marriage for both men and women.
. . Meanwhile, the U.S. marriage rate fell to 39.9 per 1,000 unmarried women in 2004 from 46.5 in 2000 and 76.5 in 1970, the study said. The ratio of married U.S. adults has fallen to its lowest since 1960, to about 55% from 69%, it said.
. . The divorce rate dropped to 17.7 per 1,000 married women in 2004 from 18.8 in 2000 and a high of 22.6 in 1980, the study said. 11% of adult U.S. women and 8% of adult men are divorced, the study said. In 1960, fewer than 3% of women and fewer than 2% of men were divorced.
. . "Put all those together, and it means that those people who marry might have a little stronger marriages than they once did, but fewer people are marrying and more people are living together outside of marriage."
. . The number of U.S. children born to unwed mothers and the percentage of children living with a single parent increased to record highs. Almost 35% of last year's babies were born to unmarried women. Of those, 40% were born to unmarried couples living together, Popenoe said. Some 40% of such couples have children.
. . Overall, the ratio of U.S. households with children has been dropping since 1960, when it was almost half. The figure dropped to about 33% in 2003 and is expected to fall to 28% in 2010.

July 13, 05: Facial attractiveness and smell give us contradictory messages about how to select mates, new research has revealed. Previous research on smell suggests that humans prefer odors from potential partners who are genetically dissimilar. But new research in which women rated the facial attractiveness of men suggests the exact opposite. So sight and smell appear to be giving contradictory messages about which partners to choose.
. . The new research investigated possible links between mate preference and the major histocompatibility complex (MHC) --the huge molecule on cells, unique to each individual, which helps our immune systems to distinguish native from alien cells.
. . The underlying theory is that humans avoid the dangers of inbreeding, and maximize the chances of having genetically fitter children, by selecting partners who have a vastly different MHC from their own. That way, there is more chance of one parent’s genes compensating for faulty genes in the other. But how the senses pick up subliminal cues about someone else’s MHC is still something of a mystery.
. . Most research so far has focused on smell, especially in rodents, and has backed up this basic assumption. Male and female mice, for example, usually select mates with different MHC, which they judge by smelling each others’ urine.
. . Smell experiments in humans have broadly given the same message, showing that body odor is more appealing in people with vastly differing MHC. But new research in which women rated the attractiveness of men’s faces has bucked the trend, showing that women preferred faces of men with similar MHC.
. . "It’s a subtle effect", says Craig Roberts of the University of Liverpool, who led the team which made the discovery. "We’re not saying it’s something that rules who we find attractive."
. . They offer an explanation to resolve the paradox, based on the notion that kith and kin --despite having similar MHC-- can offer cultural and social advantages in child rearing. The team suggests that "filtering" for mates takes place at two levels --the first based on facial likeness to select someone not too distantly related, and the second based on smell, essentially to avoid in-breeding.
. . The picture remains unclear. A study at the University of Chicago showed that women preferred odors matching the MHC of their fathers. And Wedekind showed that women taking contraceptive pills switched to preferring odors of men with similar MHC, an effect also seen in pregnant mice.

July 11, 05: Many animals copulate now and then without the delivery of semen. The act is mysterious, because animal sex is thought to be driven solely by the need to reproduce. Are they just fooling around? New research suggests there's a deeper reason. Males, it seems, are insuring their bets by encouraging fidelity and thwarting biology.
. . Tommaso Pizzari at the University of Oxford and his colleagues studied feral chickens, which are known to be rather promiscuous. The hens aren't chicken when it comes to mating with several roosters. For a male, that means sperm competition. If your favorite hen hangs out with several roosters, how do you know if you're the father?
. . Researchers outfitted one group of hens with a plastic device that prevented the fertilization of eggs. The other group had unprotected sex. Scientists watched their behavior on subsequent days. Regardless of whether semen get in, mounting alone "drastically inhibits the propensity of a hen to mate with a new rooster", the scientists conclude. Further, when hens do mate again within four days in unprotected fashion, fewer sperm reach their goal, as some natural mechanism in the hen thwarts their travels.

June 27, 05: New research finds that females of the firefly species Photinus ignitus choose males based on flash pattern in their taillights. A long burning flash means the male can offer a high quality nuptial gift –-a sperm package high in nutrients. "Females that receive high quality nuptial gifts lay lots more eggs."
. . But males of a related species, Photinus greeni, may not be so honest. The greeni males with the most desirable flash pattern do not provide the best nuptial gift. "The question now is whether the males are being purposely dishonest or signaling something else", Lewis said. "Females definitely notice the variation. They're still being choosey."
. . Male fireflies are built to mate –-basically their whole anatomy is dedicated to producing the sperm package. Making a good sperm package requires loads of energy, and most males can only produce about 10 in their short lifetime. The entire purpose of a male firefly's life is to mate, pretty much with any female that will accept them.
. . But female fireflies need to be choosey –-they only live for two weeks in their adult stage and need to make those two weeks count. The small window of time is like firefly spring break –-females will mate with multiple males and lay about 100 eggs.
. . If the greeni females aren't choosing based on signals indicating quality of the sperm package, which also contains proteins that will provide nutrients for her eggs, then what are they selecting for? "One possibility is that greeni females are not as concerned about the nuptial gift but more concerned about male genetic quality", Lewis said. "Maybe males with certain flash patterns have good genes."
. . Lewis is currently looking into whether there is sperm competition in fireflies –-whether female fireflies can choose not only which males to mate with, but which males she will actually allow to fertilize her eggs.

About 90% of the 9,700 bird species pair, mate, and raise chicks together —-some returning together to the same nest site year after year. Males, however, often raise other males' offspring unknowingly. DNA testing reveals that the social-pair male did not father 10, 20, and sometimes 40% of the chicks.
. . Only about 3% of the 4,000 mammal species are monogamous. Beavers, otters, bats, wolves, some foxes, a few hoofed animals, and some primates live together in social pairs but dally sexually much as birds do.
. . Only one species is absolutely monogamous. In the black darkness of the deep sea, the tiny male anglerfish (perhaps one tenth the female's size) detects and follows the scent trail of a female of his own species. Once found, he bites his chosen one and hangs on. His skin fuses to hers, their bodies grow together (he gets his food through a common blood supply and becomes essentially a sperm producing organ). They mate for life — a short life for the male.

June 23, 05: A married man whose wife does not go out to work but is primarily responsible for the cooking and cleaning earns about 3% more than comparably employed single men. But that wage premium disappears if wives go out to work themselves or don't do most of the housework.

June 20, 05: Breast-fed babies do seem to do better on IQ tests than formula-fed babies. Breast-feeding your baby may net the little prodigy an extra three to eight points on a future IQ test. This could translate into a 30- to 60-point edge on the SATs.

June 20, 05: A study of smells shows that the scent of grapefruit on women make them seem younger to men —-about six years younger. However, a grapefruit fragrance on men does nothing for them.

June 1, 05: It sounds like another Batman sequel: The villain sprays Gotham City with a trust hormone and people rush to give him all their money. Banks, the stock market and even governments collapse. Farfetched? Swiss and American scientists demonstrate in new experiments how a squirt of the hormone oxytocin stimulates trusting behavior in humans, and they acknowledge that the possibility of abuse can't be ignored. Those who got oxytocin invested 17% more "experiment money" than "investors" who received a placebo.
. . The findings have potential as a therapy for conditions like autism, in which trust is diminished. Or, perhaps the hormone's activity could be reduced to treat more rare diseases, like Williams syndrome, in which children approach strangers fearlessly. "Might their high level of trust be due to excessive oxytocin release?"
. . Oxytocin is secreted in brain tissue and synthesized by the hypothalamus. This small, but crucial feature located deep in the brain controls biological reactions like hunger, thirst and body temperature, as well as visceral fight-or-flight reactions associated with powerful, basic emotions like fear and anger. For years, oxytocin was considered to be a straightforward reproductive hormone found in both sexes. In both humans and animals, this chemical messenger stimulates uterine contractions in labor and induces milk production. In both women and men, oxytocin is released during sex, too.
. . Then, elevated concentrations of the hormone also were found in cerebrospinal fluid during and after birth, and experiments showed it was involved in the biochemistry of attachment. It's a sensible conclusion, given that babies require years of care and the body needs to motivate mothers for the demanding task of child-rearing.
. . In recent years, scientists have wondered whether oxytocin also is generally involved with other aspects of bonding behavior —-and specifically whether it stimulates trust. Trust is the glue of society and human interactions. Erase it, and you compromise everything from love to trade and political order. "I once likened trust to a love potion", Damasio writes. "Add trust to the mix, for without trust there is no love."

May 31, 05: Sex and romance may seem inextricably linked, but the human brain clearly distinguishes between the two, according to a new study. The upshot: Love is the more powerful emotion. The results of brain scans speak to longstanding questions of whether the pursuit of love and sex are different emotional endeavors or whether romance is just warmed over sexual arousal.
. . "Our findings show that the brain areas activated when someone looks at a photo of their beloved only partially overlap with the brain regions associated with sexual arousal", said Arthur Aron of the State University of New York. "Sex and romantic love involve quite different brain systems." Romance seems to steep in parts of the brain that are rich in dopamine, a chemical known to affect emotions. These brain regions are also linked by other studies to the motivation for rewards. "To our surprise, the activation regions associated with intense romantic love were mostly on the right side of the brain, while the activation regions associated with facial attractiveness were mostly on the left."
. . The study also revealed that as a romance matures, so does the mind. "We found several brain areas where the strength of neural activity changed with the length of the romance", Brown said. "Everyone knows that relationships are dynamic over time, but we are beginning to track what happens in the brain as a love relationship matures."
. . Study member Helen Fisher, an anthropologist at Rutgers University, said the study might suggest some of the physiology of stalking behavior. Other studies suggest that up to 40% of people who are rejected in love slip into clinical depression, she said.
. . Some of the changes seen with mature romances were in regions of the brain also associated with pair-bonding in prairie voles. Other studies have found that expressions of attraction in a female prairie vole are linked to a 50% hike in dopamine activity in the brain region that corresponds to the location where human romance is processed. "These and other data indicate that all mammals may feel attraction to specific partners, and that some of the same brain systems are involved", Fisher said.

The British science writer Philip Ball has won the prestigious 2005 Aventis Prize for popular science books. His publication, Critical Mass: How One Thing Leads to Another, is an exploration of human behavior and the nature of decision-making. In Critical Mass, Mr Ball argues that the application of the laws of modern physics to the study of human nature can enrich our understanding of how people behave.

May 11, 05: You might think it's grand to be a well endowed fish --if ya gotta be a fish. After all, some female fish prefer mates with larger sex organs, a new study finds.
. . But the guys' prowess has a price. The studs with larger gonopodia, which is what scientists call male fish sex organs, can't swim as fast as their less impressive counterparts, so they're more likely to get eaten by predators.
. . Data in hand, Langerhans exposed about 50 females, one at a time, to video images of a male of average proportions at one end of an aquarium and an outsized male at the other end. "They chose the larger one over and over", Langerhans said. "All females had the same preference."
. . Mosquitofish bear their young live, bypassing the whole egg-in-the-gravel hassle. Among such livebearing fish species, gonopodia range from less than 20% of a fish's body length to more than 70%. Don't ponder that too long, but trust that it fits into an evolutionary puzzle that spawned this study.
. . What is a gonopodium? "In the sense that gonopodia are sperm-transfer organs, they are analogous to a mammal penis."
. . There's a larger point to this research. Male genitalia, scientists tell us, come in many shapes and sizes, with more variety than most body parts. These differences are sometimes the best way to distinguish one species from another.
. . For years, experts have figured that this remarkable diversity in genitalia had to do with sperm competition or some other after-the-act effect. The new study shows that female fish, like women, make some decisions beforehand --conscious or not-- about the physical dimensions of the fathers of their children. "Overwhelmingly that choice is made with size being the prize", Langerhans and his colleague report on the little guppies.
. . So perhaps, the logic goes, differences in male genital shape between populations lead to "reproductive incompatibility", which means two groups would split and become separate species. Langerhans is now looking into this possibility in other creatures.

"Women look best once a month"
. . In a study conducted at the University of Newcastle, 51-59% of male and female subjects preferred photos of women at their peak fertility in their cycle to (unlabeled) photos of the same women 14 days later.

Apr 13, 05: Young men who think that driving fast or doing a bungee jump will impress the girls would probably do better to talk about making a top-up to their pension scheme.
. . Far from liking men who take pointless risks, girls prefer men who are cautious, according to new research. The findings knock the mainstream theory that, like animals in courting rituals, men who display strength and courage are showing off their genetic fitness to potential mates. That notion fits in nicely with the fact that men in their prime reproductive years, from the late teens to the late twenties, take more risks.
. . However, University of Maine researchers, who surveyed 48 young men and 52 young women on their attitude to risky scenarios, found women preferred cautious men.
. . "Men thought women would be impressed by pointless gambles. The only people impressed by their stunts are other men." If so, another, subtler theory may explain this paradoxical behavior. By gaining plaudits from other men, the risk-taker gets higher social status, and this is a known lure for women.

Mar 17, 05: When male animals strut their stuff —-the rainbow plumes of peacocks, the mighty tusks of an elephant-— they might be flaunting their potential for fatherhood, researchers in Spain say. The team found a direct link between the length and complexity of a buck's horns and the quality of its sperm. Long, multi-pointed antlers on a buck signal that it is a potent mate and females might seek out such males for this reason. He cited peacocks as candidates for further study.

Dec 22, 04: New research is now showing that genetic and biological factors play an equal, if not greater, role than social factors in crime causation. Within this new field of biocriminology, brain imaging findings are revealing dramatic new insights into the criminal mind.
. . There are now 71 brain imaging studies showing that murderers, psychopaths, and individuals with aggressive, antisocial personalities have poorer functioning in the prefrontal cortex --that part of the brain involved in regulating and controlling emotion and behavior. More dramatically, we now know that the brains of criminals are physically different from non-criminals, showing an 11% reduction in the volume of grey matter (neurons) in the prefrontal cortex.
. . Over 100 twin and adoption studies have convincingly shown that genetic processes account for 50% of antisocial and criminal behavior. Of the remaining half that is environmental, biology accounts for part of this. For example, physical child abuse can cause brain damage that in turn results in antisocial, aggressive behavior.
. . There is exciting new evidence that an abnormality in one specific gene (monoamine oxidase A), when combined with child abuse, predisposes to violent offending in adulthood. In a similar fashion, birth complications, when combined with maternal rejection in the first year of life, results in higher violence at age 34.
. . The biological and genetic findings are now incontrovertible; the evidence is too strong to ignore. These new breakthroughs have important implications for crime prevention.
. . New research has just shown that childhood malnutrition is linked to poor brain functioning (low IQ) and conduct disorder in early adulthood. Giving three-year-olds better nutrition (and more physical exercise) for just two years results in better brain functioning (EEG) at age 11, and a 35% reduction in crime 20 years later at age 23. Prisoners given fish oil (rich in omega-3, a long-chain fatty acid that is critical for brain structure and function) show reduced aggressive and antisocial behaviour.
. . If we really want to stop crime, the best investment society can make is to intervene very early on. Better prenatal and perinatal health care, better nutrition early in life, and medication for severely aggressive children can be implemented right now.

[Monogamous marriage is a compromise that attempts to give society --not individuals-- the best overall experience. It is a failure. But the fact that it has survived for 10-2- centuries is evidence that it is the best failure we have. On the other hand, what is the compromise, exactly?] Of the 1,170 human societies cataloged in Murdock's Ethnographic Atlas, over 72% permit multi-spouse relationships. See the file.

From http://www.lovethatworks.org/FAQ.html
. . Tertullian (A.D. 160?-220?) Marriage would not even be recognized as a sacrament by the Catholic Church for another 1,000 years --until 1215; divorce would not be absolutely proscribed for another 500 years after that.
. . Plow (as opposed to hand cultivation using "digging sticks" and the like) agriculture marked the fundamental turning point in the creation of a sexual double standard that cemented monogamy in place and relegated women to a subordinate role. It emphasized the male role because generally only men had the strength to operate the animal-driven plow effectively, and de-emphasized the female role of providing for the family by foraging. As Helen Fisher notes, "With the advent of plow agriculture, neither husband nor wife could divorce. They worked the land together. Neither partner could dig up half the soil and depart. They had become tied to their mutual real estate and to one another –-permanent monogamy."
. . The average length of a colonial marriage, principally due to high mortality rates, was less than a dozen years. One third to one half of all children lost at least one parent before the age of twenty-one.
. . In 1940, one in ten American children lived with neither biological parent. By the 1990’s, that figure had fallen to one in twenty five.
. . The monolithic monogamist view that "easy" divorce is shortening the duration of nuclear families is belied by the evidence of the past. Just taking into account shortened lifespans, nuclear families were intact for shorter periods historically than is true today.
. . In the 1820's, per capita consumption of alcohol was almost three times higher than it is today.
. . The rate of live births to teenagers 15-19 in 1997 was 52.9 per 1000. It was 90.3 per 1000 in 1955.
. . According to a General Accounting Office report issued on January 31, 1997, there are no fewer than 1,049 "federal laws in which benefits, rights, and privileges are contingent on marital status."

July 1, 04: Semen makes you happy. That's the conclusion of a study comparing women whose partners wear condoms with those whose partners don't. The study showed women who were directly exposed to semen were less depressed. Researchers think this is because mood-altering hormones in semen are absorbed through the vagina. They say they've ruled out other explanations.
. . The team divided 293 female students into groups depending on how often their partners wore condoms, and assessed their happiness using the Beck Depression Inventory, a standard questionnaire for assessing mood. People who score over 17 are considered moderately depressed.
. . The team found women whose partners never used condoms scored eight on average, those who sometimes used them scored 10.5, those who usually used them scored 15 and those who always used them scored 11.3. Women not having any sex scored 13.5. Gallup said his team already has unpublished data from a group of 700 women confirming the always-use group was more depressed than the usually use group, suggesting the discrepancy in the smaller study was a sampling error.
. . The team also found depressive symptoms and suicide attempts more common among women who used condoms regularly compared with those who didn't. The results will appear in the journal Archives of Sexual Behavior.
. . But is it really semen that affects women's mood? Researchers say they looked at alternative explanations, such as whether women who seldom use condoms took oral contraceptives, how often they had sex, the strength of relationships, and the possibility a certain type of personality influenced the decision to use condoms. But none of these factors can explain their findings, they say.

June 17, 04: In a remarkable experiment in hormone chemistry, behavioral scientists implanted a single gene into promiscuous male voles, transforming them at a stroke into faithful, attentive and caring partners. The rodent in question is the meadow vole --and he is the original love rat. He thinks nothing about mating with several females at once and leaving them to rear his offspring while he wanders off in search of his next conquest. In contrast, the meadow vole's cousin, the prairie vole is a model of fidelity.

Dec 19, 03: The toadfish, which can be found in the North Pacific from California all the way to Alaska, makes the humming sound by vibrating a set of sonic muscles on its air bladder 6,000 times a minute for more than an hour at a time, an amazing combination of speed and endurance. The human heart, by contrast, beats about 60-80 times a minute.
. . There are two types of male plainfin midshipman, which he labeled Type 1 and Type 2. Type 1 males make the noise, staking out "nests" in shallow water, waiting for a female to approach and then, after the female lays individual eggs on the rocks above, fertilizing each one in a process that can take 20 hours. The Type 1 male then watches over the eggs until they hatch.
. . Type 2, or "sneaker" males are, to be blunt, cads. They don't hum but hang around Type 1 males until a female approaches. During the fertilization process, sneaker males try to fan some of their sperm onto the eggs before taking off.

Nov 11, 03: New study: Parents who were living with an opposite-sex spouse or partner before the child’s conception or birth were significantly more likely to have a male child than parents who were living apart.

. In the most extreme cases of low-investment parenting, the menfolk simply impregnate women at random, then wander off in search of other women, a state of affairs(!) that can be sustained society-wide only in lush [,not over-populated] climates where women are able to provision themselves and their infants without too much trouble. In a piece of informal jargon I like very much, anthropologists contrast male practitioners of the the low- and high-investment styles as "cads” and “dads", respectively.
. . Dads were described as domestic, happy, peaceable, bookish, moral, gentle, compassionate, frank, and shy. The Cads came off as daring, arrogant, moody, passionate, rebellious, strong, humorous, vulgar, shrewd, and slanderous.

See the entire file that's excerpted below.
. . (...in science and literature): What do women really want? Well, it depends, says Daniel Kruger's latest findings of what women look for in a man. When looking for a short term relationship, women prefer "the classic Romantic dark heroes who are dominant, promiscuous and daring". where as long-term relationship seeking women prefer "men who are kind, compassionate and monogamous". It's the distinction of "cads" vs "dads", and Kruger says it may play an important role in evolutionary mating theories.
. . "About 60% of the women said they would prefer to have sex with a cad when considering a brief affair", said Daniel Kruger, a social psychologist at the U-M Institute for Social Research (ISR), the world's largest academic social science survey and research organization. Only 13% of the women said they would prefer to see an imagined 25-year-old daughter engaged to a cad. "A cad would be less likely to provide paternal support for offspring."
. . According to Kruger, the findings imply that the dad versus cad distinction is intuitive to women and remains a key element of contemporary mating strategies. Women's preference for cads for short-term relationships supports what evolutionary psychologists call the "sexy son hypothesis". Kruger said. Even though cads aren't good bets to stick around and help raise children, the genes that make men successful cads will be passed along to their sons, who will increase their mothers' eventual reproductive success by providing numerous grandchildren.
. . Recent research on human sexuality suggests that humans evolved to pursue both short-term and long-term, or cad and dad, mating strategies. Considerable evidence suggests that, unlike most mammals, humans are designed for long-term sexual relationships with substantial male parental investment in children.
. . Aspects of both men's and women's sexuality show that humans did not evolve exclusively to pursue long-term mating. Men consistently show a marked desire for sexual variety. A successful womanizer in the environment in which humans evolved would have been able to sire a large number of children, many of whom would likely have survived despite higher mortality risks, especially in a resource-rich environment. The cad mating strategy has been shown to be successful in some circumstances.
. . Draper, Harpending, and Belsky have argued that men evolved to specialize in one of the two mating strategies and have found that, cross-culturally, cads and dads show distinct clusters of personality traits. They believe that cads and dads are different human morphs, just as workers and queens are different morphs of ants, and that whether a man becomes one or the other depends on an environmental trigger: the presence or absence of the father in the household where the son grows up. The sons of father-absent households will become cads, and those of father-present households will become dads.

Oct 15, 03: It may not be condoned in most societies, but scientists said today that female promiscuity is not all bad, because it helps to create healthier offspring --at least in birds.
. . Like humans, birds are mostly-monogamous creatures that usually choose one mate and stay with them to raise their young. But scientists at the Max Planck Research Center for Ornithology in Starnberg, Germany said some female birds prefer more than one mate, to improve their chances of producing fitter young, a finding that could have implications for better understanding human sexual behavior.
. . They noticed that when female birds were paired with young males, they were more likely to be unfaithful with older or bigger males, and that the young they produced were more likely to survive to the next breeding season. When the offspring matured, if they were females, they produced more eggs than the other birds; and if they were males, they had a more attractive feather crown, a big draw with the ladies.
. . "Our research suggests that females are promiscuous, or unfaithful to their partners, to avoid negative effects of in-breeding. He believes the female birds have a way of assessing the quality of their partner and if they are not happy, they look elsewhere for potential mates.
. . "We have good observations to show it is really the females that are playing the active role. It's not exactly a night out on the town, but the researchers spotted female birds going out early in the morning when it was still dark and when all the males were singing in the dawn chorus. ... It is during these early morning hours, when they are fertile, they go out and seem to look for particular males to copulate with", he added.
. . The next big question the researchers hope to answer is whether promiscuity in females has some sort of genetic basis, or whether it is related to personality.
. . Kempenaers said fidelity still exists in some species, notably swans and sea birds such as the albatross that mate for life and are never unfaithful to their partners. But he added: "That is seen now as more the exception than the rule."

Aug 7, 03: Size is usually more of an issue but the shape of the penis is also important because it evolved to dispel other men's semen, according to scientists in the US. "They found that the coronal ridge... could scoop out more than 90% of the cornstarch mixture (from the artificial vagina) with just one thrust, while a phallus with no coronal ridge only managed to remove 35%", New Scientist magazine said Gallup and his team, who reported their finding in the journal Evolution and Human Behavior, said the depth of penetration was also important in expelling more semen.
. . Their findings were supported with surveys of students who were questioned about their sexual experiences. "Sexual intercourse often involved deeper more vigorous penile thrusting following periods of separation or in response to allegations of female infidelity", they said.
. . [I realize now that this capability is also a good reason why the man must lose the erection immediately --if he didn't, he'd remove his own semen. Hormones are now known to bring on sleepiness at that time. -JKH]

Aug 21, 02: If you are worried about jealousy ruining your love life, here's the latest scientific advice: try measuring your partner's ears. Or feet. Researchers have found that asymmetrical people are more likely to be jealous in love than those who are symmetrical. Scientists have long shown that people whose faces and bodies are the same on both sides are considered more attractive and have an easier time attracting mates. Brown found that lopsided people were considerably more likely to be jealous lovers, with symmetry possibly accounting for 20% of the difference in romantic jealousy between people.

June 20, 02: Seeing smiling faces makes the brains of extroverted people light up more than the brains of shy people, researchers said in a study they believe could help shed light on the biology of personality differences. Specifically, the amygdala, a small region of the brain associated with emotional response, lights up when an outgoing person sees a picture of a smiling face. "This study shows for the first time that the same facial expression can be processed differently by different people, according to their personality." Now Canli has to answer a chicken-and-egg question --are extroverts outgoing because they are hard-wired to get pleasure out of smiling faces, or do they respond to smiling faces because they are outgoing?

May 22, 02: Women interested in knowing whether their men are likely to stray should find out their testosterone levels. In birds, low levels of the male hormone encourage fidelity while higher levels mean they are more likely to play the field, and the same could hold true for humans. Scientists at Harvard University have discovered that married men who spend time with their family have lower testosterone levels than bachelors.
. . Dr. Gray believes it could work both ways. Lower levels encourage men to spend time with their family and being in a family may lower the hormone levels. In his next project, he plans to study levels of the hormone in men separated from their wives but who have joint custody of their children to separate the impact of marriage from parenting.

The World Health Organization estimates that 500 million people around the world suffer from a psychological disorder. They estimate that only 100 million couples engage in sexual intercourse on an average day, which is only 3.3% of the world's people. [Sounds like a connection to me!]

June 24, 03: In tests conducted at New Mexico State University, it became evident that women have a predilection to choose certain types of mates depending on varying facial characteristics, as well as certain points in their menstrual cycles. Women identify one set of male faces as desirable at one stage of their fertility cycles, but pick a slightly different set of faces at another stage of their cycles. They also select different males for short- and long-term mates. Some of his students also plan to study the facial preferences of gay women, women past menopause and women taking birth control pills. (Men, Johnston noted wryly, tend to prefer the same 25-year-old face no matter how old they are.)
. . "We are bombarded by hundreds or thousands of images of members of the opposite sex who are wildly attractive", Dr. David Buss says. "And there is some evidence that hyper exposure to these images decreases people's attraction to their regular mate."

4-25-01, New Scientist magazine: Women stay in monogamous relationships for security and men stay in them for sex, a science journal says. "It's a cynical view of human relationships, but researchers now say it is the driving force behind the evolution of monogamy --and women started it".
. . In most species, females only have sex when they are fertile and males know through visual and chemical cues when the time is right. When it is not, males look elsewhere. But in birds, porcupines and humans, females have sex whether they are fertile or not. They found that monogamy is often the top choice when fertility is hidden, even among males who are used to having many partners.

Dr. David Buss, the author of Evolution of Desire, a massive cross-cultural study into human sexuality:

. . "Both sexes have what I call a short-term mating strategy and a long-term mating strategy", Buss says. "The short-term mating strategy involves casual sex, one-night stands, you know, brief sexual affairs. Long-term mating strategy involves commitment, marriage, and the emotion of love. And these are two very distinct programs."
. . Buss suggests these programs are etched into our behavior by millions of years of trying to get our genes passed on to another generation.

The long...
. . For men, a long-term strategy is to find a kind, intelligent, attractive woman, who will pass on good genes and care for children. However, Buss is quick to point out that these aren't conscious decisions. "Men aren't consciously thinking: Oh, I want a woman who's fertile and reproductively valuable, but the things that they're attracted to --things like physical appearance and youth-- provide a wealth of cues that convey fertility and reproductive value. Things like clear skin, good muscle tone, signs of health, clear eyes, and so forth", Buss explains.

A man's ideal long-term mate: intelligent, attractive woman, who will be a good mom. Men are not only looking for physical health, however. "They want a long-term mate who will be cooperative, who will be intelligent, who will be kind, who will be a good mother to their children, and who will be emotionally stable", Buss says. "But physical attractiveness, physical appearance is extremely important in men's search for a long-term mate."

A woman's long-term strategy is to find a kind man who is a good provider, and who loves her and only her --lest she lose resources. "Women like men who have some goals and drive and want to get ahead in the world. These men are reliable providers of resources over time", Buss says. "But women also go for men who are in love with them. This love issue is a critical issue that kicks in only in the long-term mating context. One of the central functions of love is that it's a signal of commitment to her. The guy's in love with her, then the chances are he's going to stay with her through thick and thin." Again: resources.
. . A woman's ideal long-term mate: driven, reliable provider who's in love with only her.

... and the short of it:
. . However, both men and women have short-term strategies. Men seem to be programmed to want sexual variety. They want to spread their seed as far as possible so that it has a greater chance of moving down the line. "Men could just walk down the street and pass six different women and find themselves sexually attracted to each of those six different women", Buss says. He is quick to add, however, "Whether we act on those desires is a different issue."
. . Women also have short-term strategies. "This may sound really harsh, but in the economics of the mating world, women can have short-term sex with men who are far more desirable than their regular partner", Buss says. Stated differently, a woman can attract a more desirable sex partner more easily than she can a husband. "What that means is, in an ideal world, one optimal strategy for women is to marry one guy and secure all of his resources and commitment while cuckolding him with a genetically superior male", Buss continues. "So, she gets the best of both worlds --resources from one guy, good genes from another guy. And some women, in fact, do that."

When sex and love collide: it's a difference between short- and long-term strategy.
. . Buss has some evidence to back this statement. "We know from the DNA fingerprinting data that 10% --and this is a rough figure-- but 10% of all people now have genetic fathers that are different from their social father, so to speak."
. . Humans are, of course, creatures capable of making decisions, and we don't automatically act on all of our urges. There are many reasons people cheat on a spouse, but evolutionary influence does show up in some extramarital affairs.

What's happiness got to do with it?
. . "Women who are happy with their relationships typically do not have affairs. Now this may seem very obvious, but the interesting thing is when you look at men and compare men who have affairs, with men who don't have affairs, there is no difference in their level of marital happiness", Buss explains. "What that means is that some men who are perfectly happy with their marriage can still have affairs on the side and try to satisfy that desire for sexual variety, even if they are in love with their wife and have no desire whatsoever to leave her."
. . Again, men aren't consciously thinking, "Hey, I'd like some sexual variety." These thoughts are maneuvering below their radar, exerting their evolutionary force.

Recent research challenges
notion of female monogamy
. . Carol Cruzan Morton, Special to The Chronicle
. . (sorry, donno which city's Chronicle)

Females of many species, it turns out, have evolved strategies for passing on their genes that involve copulating with multiple males --and recognition of that fact is literally changing our view of the birds and the bees.
. . "Natural selection, it seems, often smiles on strumpets", says evolutionary biologist Olivia Judson, author of "Dr. Tatiana's Sex Advice to All Creation", the most recent and entertaining book exploring the variety of female harlotry. "As a rule, loose females have more and healthier children."
. . To be sure, biologists are examining these questions in the dispassionate light of scientific inquiry. In describing their theories, they prefer the more neutral term "polyandry", meaning many males, instead of "promiscuity." And they caution laypeople not to look to nature's own apparent infidelities for any justification of their own behavior.
. . The misbegotten idea that males evolved to make love and females to demur gained scientific currency in the late 1940s in fruit fly experiments by Angus Bateman, a British scientist who reached his erroneous conclusions in part because his experiments lasted only three or four days.
. . Had he run his experiments longer, he might have discovered that male black-bellied fruit flies secrete an anti-aphrodisiac [!] in their semen that's relatively short lived. As soon as it runs out, females become interested in copulating again. On the surface, the conventional view made sense. Sperm seemed to come cheap to males, while eggs were expensive to females, which have to invest the time to raise offspring. Scientists could not fathom any possible benefit of multiple partners of females, and they could come up with plenty of potential costs, such as sexually transmitted diseases.

BIRDS DO IT
. . Then came DNA paternity testing. In one species after another, it turned out that biologists were as cuckolded as the males they had been observing. The first and most extensive examples of polyandry were found among avian species, which was quite a shock to scientists because birds had appeared to be paragons of traditional family values.
. . "The way the male and female rush back and forth to their demanding brood of chicks seems like nature's model of good parenting", says Marlene Zuk, biology professor at UC Riverside and author of "Sexual Selections: What We Can and Can't Learn About Sex From Animals." ... "Now, we find that they're actually in the same situation as millions of modern-day husbands and wives, eyeing a child warily and making uneasy jokes about the milkman", she says.
. . DNA testing in chicks of seemingly monogamous females showed a wide range of extra mates. In one study, for example, as much as 90% of the offspring of the brilliantly colored Australian fairy wren were from mates other than the presumed father.
. . Biologists have struggled to come up with broad theories for why females benefit from playing the field, but so far the reasons seem to vary widely according to species. A lot of complex theory boils down to this: A gal's got to do what's necessary to ensure the survival of her genes.
. . In some cases, females may get more help around the home. Among bronze-winged Jacana, for example, harems of up to four males do all the child care, enabling a female to have four times as many broods. Male Greater Rheas, flightless South American birds that resemble ostriches, receive eggs from several females, incubate them and rear all the chicks, while females go off to mate and lay other clutches. In other cases, females swap sex for food --the more sex, the more food and the healthier their offspring.
. . Among green-veined white butterflies, for example, a virgin male ejaculates a sperm packet roughly 15% of his weight that also contains nutritious substances. Females that have sex with several virgins lay more and bigger eggs than those that do it with only one or with males that have lost their virginity and consequently make sperm packets only half the size of their virgin glory.

SURVIVAL OF THE LOOSEST
. . In other cases, promiscuity is simply a matter of survival. Male chimpanzees & lions, for example, have been known to kill infants not their own. Frequent sex with several males --in one 15-minute period, a chimp female was observed having sex with eight males-- can heroically confuse paternity and act as insurance against harm to her offspring.
. . But while females are busy ensuring their genetic survival by sleeping around, males have not been idle. After all, female promiscuity puts the genes of males at risk. It's no good being Don Juan, seducing all the females in sight, if none of them uses your sperm, Judson says. So males have developed counterstrategies to ensure their genetic survival.
. . "This is perhaps the most significant discovery of the past two decades, that male and female attributes coevolve", writes Tim Birkhead, professor of behavioral ecology at the University of Sheffield in Britain and author of "Promiscuity: An Evolutionary History of Sperm Competition."

SOME MALES' WEAPONS LETHAL
. . In the arms race between the sexes, males of some species have developed penises that are more than sperm delivery devices.
. . Damselflies, close relatives of dragonflies, have penises with inflatable balloonlike bulbs, two horns at the tip and long bristles down the sides. In one species, males use this to scour sperm from inside a female before depositing his own. In another, males use it for extra stimulation, inducing her to eject sperm from previous lovers.
. . Male honeybees, on the other hand, sacrifice themselves on the altar of love. Upon climax with the queen, he explodes, and his genitals rip from his body, leaving the mutilated member as a kind of chastity belt. "You might imagine that male honeybees would have evolved some way of removing the chastity belt. You'd be right", Judson says. "If you look closely, you'll see that each male honeybee sports, on the tip of his phallus, a hairy structure that can dislodge the severed genitalia of his predecessor."
. . Other species resort to guarding their mates. A possessive postcoital male Idaho ground squirrel, for example, won't let his partner out of his sight and follows her everywhere, stationing himself at the entrance to her burrow and picking fights with other males that happen to come near.
. . When it comes to Homo sapiens, scientists urge us not to read too much into all this. Depending on their point of view, people may be horrified or intrigued by the infidelity of the birds and the bees, but in truth birds aren't cheating, they're just doing what they do.
. . "If we try and use their behavior as a model or justification for our own", says Zuk, the UC Riverside biologist, "we not only run the risk of making decisions about our morals on very shaky grounds, we miss what is interesting and vital about the animals' own behavior."

NEW LOOK AT REPRODUCTION
. . Females of many species have sex with multiple partners. Males, in turn, have adapted ways to ensure that their genes, and not those of competitors, are passed on. Understanding this co-evolution is changing our view of male and female sex roles.
. . Among reed buntings, small brown songbirds, every male a female has mated will come flying to her defense. But her infidelity can backfire if the female's main squeeze suspects her of cheating. ==========

LINKS:
. . The first season of The Sex Files (Discovery Channel) explored a whole episode on The Affair. Check it out for other influences on marital infidelity.

Here's a basics tract.
And a professional site on Evolutionary Psychology.

Also, of course, see the sex file on this site.

Skip down to "A cogent explaination from the Discovery Channel.".

When you read, take care not to judge based on your desire to believe that viewpoint, be it opposite yours, or just different. Read Dawkins' "The Selfish Gene" (See excerpts.)) or Wilson's seminal "Sociobiology".

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