Kevin Callahan's Lab Notebook
Fall Quarter 1997
(c) 1997 Kevin L. Callahan
Lab 1 Notes Fall 1997
Lab 2 Notes Fall 1997
Lab 3 Notes Fall 1997
Lab 4 Notes Fall 1997
Lab 5 Notes Fall 1997
Lab 6 Notes Fall 1997
Lab 7 Notes Fall 1997
Lab 8 Notes Fall 1997
Lab 9 Notes Fall 1997
Lab 10 Notes Fall 1997
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Lab 1 Notes Fall 1997
Anthropology 1101
HUMAN ORIGINS
The Physical Anthropology Laboratory: Room 20 Ford Hall
Welcome to Anth. 1101 Human Origins
Kevin L. Callahan
Email: call0031@tc.umn.edu
Index Card Information
Please fill out the index card with:
Your Name
A phone number (optional)
Your Major and Year in school
Any prior biology or anthropology courses
Are you a day or extension student
2 abiding interests in life
Kevin Callahan
Ph.D. candidate in Anthropology
Archaeology MA in 1995
Interests: International rock art studies
Research areas, MN, Scotland, Hawaii
Please call me by my first name.
How to reach me
Info is in the syllabus and U of M Phone book
Email call0031@tc.umn.edu
Office: 275 Ford Hall
Office phone: 625-0166
Office hours
The hour and a half just before my labs on Thursday and Friday
2:00 to 3:30 pm Thursday and Friday
Room 275 Ford Hall
Introduction to major course themes
Human evolution; change over time
Physical (biological) and cultural developments
Fossil primates to Homo sapiens
Over ten million years (= >10 my)
Anthropology 1101 Lab 1: Natural Selection
Introduction
In this lab we will introduce you to the topic of natural selection, the
evolutionary mechanism that results in adaptation.
As you will see, one of the conditions for natural selection is that traits
have a genetic basis (they can be passed to future generations).
Major Topics of Discussion
anatomy
genetics
primatology
early fossils
archaeology
early subsistance,
social behaviors and
symbolism
Course Organization
Read the lab manual before the lab!
Take notes in lab!
Do not miss a lab! Attendance is taken
Go to the lab you are registered in.
Bring pen, paper, and a calculator.
Bring a ruler in cm and inches.
Get some graph paper.
Lab is FUN!
Anth. 1101 Human Origins class website
Type in "Human Origins" in Yahoo!
Address http://www.oocities.org/Athens/Acropolis/5579/TA.html
Website addresses are case sensitive (type addresses exactly)
There are free computer labs
ANTH. 1101 WEBSITE
THERE ARE FREE COMPUTER LABS ALL OVER THE CAMPUS
IF YOU HAVE ANY QUESTIONS EACH LAB HAS AN ATTENDANT.
My Educational Approach
Use visual, auditory, tactile, color and emotional retention of info. i.e.
Use different parts of the brain
attention spans have limits
repetition of concepts in text, lecture & lab
some memorization is required e.g. know your bones & species
USEFUL HOME VIDEOS
"IN SEARCH OF HUMAN ORIGINS"
w/ DON JOHANSEN
ON PBS VIDEO
"APE MAN"
w/ WALTER CRONKITE
ON A & E VIDEO
Geography and site maps are important
RULES OF THE LAB
PLEASE! NO FOOD OR DRINKS (We are trying to avoid insects coming into the lab).
PLEASE! BE CAREFUL WITH THE SPECIMENS!!! (They are expensive and many students
will be handling them).
READ YOUR LAB MANUAL BEFORE COMING TO LAB
THERE ARE READING ASSIGNMENTS WITH SOME LABS
ASK QUESTIONS
GET TO KNOW YOUR LAB PARTNERS
Anthropology
The study of human beings
The 4 fields of Anthropology
Physical or Biological Anthropology (evolution, human biology).
Archaeology (the study of the material culture/behavior of early human beings).
Cultural and Social Anthropology (the extrasomatic means of adapting to the
environment through culture and society)
Linguistics (the study of the human use of language)
Introduction
Evolution is "change over time in the characteristics of a group of organisms"
Evolution is just change. It is not necessarily improvement or progress.
What is a species?
A species is "a group of organisms that can mate and produce fertile offspring
among themselves but not with other groups."
A species is reproductively isolated from other groups.
A horse and a donkey can mate and produce a mule, but mules are infertile
hybrids and cannot bear young.
The History of Evolutionary Thought
Pre-Darwin
Before Darwin
The Pre 1700’s view was that species did not change and the Earth was not very
old.
In 1650 Archbishop James Ussher determined that the world was created on the
night before Oct. 23rd in the year 4004 b.c.. The Earth was believed to be less
than 6000 years old.
CHARLES LYELL -geology
Principles of Geology
Uniformitarianism
1830-31
Uniformitarianism - Summary
Uniformitarianism is the concept that biological and geological processes that
affected the Earth in the past still operate today
The Earth was much older than previously thought.
Thomas R. Malthus
1830 Essay on the Principle of Population
Population increases geometrically, and faster than the food supply which
increases arithemetically leading to a struggle for resources. Overpopulation
is kept in check by disease, famine, and war.
Malthus profoundly affected Darwin and Wallace who realized this was the key
to understanding the evolutionary process.
Jean Baptiste Lamarck
1801 Theory of Acquired Characteristics
aka the "hopeful monster theory."
Giraffes stretch their necks and they grow longer.
The theory is incorrect.
Theory of Acquired Characteristics - Lamarck
(1744-1829) Coined the term "biology"
Lamarck correctly recognized that organisms and their environment are in a
dynamic relationship.
He proposed an incorrect progressive mechanism of biological change.
The error in Lamarckian thinking
The theory of inheritance of acquired characteristics suggests animals change
their bodies or create new organs through repetition and "will power" so that
giraffes have long necks because they somehow "will" it and pass the longer
necks on to succeeding generations.
Bodybuilders kids don’t inherit bulging muscles. It does not work that way.
Darwin
Charles Darwin would build his theory of the evolution of species on the work
of many others such as Burnett, Hooke, Linneaus, Malthus, Buffon, Hutton, Lyell,
Cuvier, Lamarck, and others.
Charles Darwin and Alfred Russel Wallace’s
Theory of Evolution
Charles Darwin - Evolution & Natural Selection
A.R. Wallace - 1858
Independently came up with a similar theory of evolution based upon natural
selection.
Darwin and Wallace agreed to publish papers on the same day at the same
conference.
Darwin and Wallace
Darwin came up with the theory in 1836 but delayed publishing it until Wallace
in 1858 threatened to go public with a similar theory. They agreed to present
the idea simultaneously.In 1859 "On the Origin of Species by Means of Natural
Selection" was published by Darwin.
Darwin and Wallace
As a result of separate world travels, observations, and reading they
independently noted 2 facts.
1) Individual organisms within a species exhibit variation.
2) Linnaeus’ similarities and differences represent biological relationships of
descent from previous organisms.
The Voyage of HMS Beagle
Charles Darwin’s trip around the world
1831-1836
Visited the Galapagos Islands
On the Origin of Species by Means of Natural Selection
Organisms are adapted to their environments.
Organisms undergo adaptive change when the environments change.
Variation already exists in populations.
Natural Selection
Nature "selects" from the existing variation those individuals who by chance
are best adapted to the environment.
Those individuals who are best adapted to the changed environment are the most
reproductively successful, produce the most offspring that survive, and pass on
their adaptive traits.
Natural Selection
The most adaptive traits of a species tend to increase in frequency.
The less adaptive traits tend to decrease.
Evolution has no particular direction such as evolving into more complex or
"progressive" forms.
Natural Selection
The variation from which nature selects is random - not willed by the organism.
If populations are geographically isolated in different environments there will
be different selective pressures.
The changes selected for accumulate through time and may result in populations
so different they cannot interbreed and produce fertile offspring.
On the Origin of Species by Means of Natural Selection
Environmental change can result in new species.
Since the process is based upon random variation species do not always
successfully adapt to changes in the environment.
If no preadapted variation is available the species becomes extinct. More than
9/10ths of species are now extinct.
Hominid extinctions
A "Hominid" is a primate that habitually walks upright on 2 legs - humans are
hominids.
Homo sapiens is the only hominid left that is not extinct.
2 million years ago 4 hominids lived at the same time.
Peppered Moth camoflage
Natural selection is illustrated by the increased survival rate of moths that
blend in with their backgrounds. Where light (lichen covered) trees were
blackened by industrial soot the dark moths became more common.
Gaps in Darwin’s work
Darwin and Wallace did not understand the mechanism of genetic transmission of
traits or the reason for individual variation within a species.
Gregor Mendel (1866) discovered that traits are inherited as discrete units
(genes) and are not blended. Mendel worked out the particulate nature of
inheritance.
Genes
A gene is just a section of a DNA molecule. The genes control production of
proteins and enzymes which make up the body and control its chemical processes.
The DNA molecule is the only self reproducing molecule we know of (its what life
"is" in some sense).
We will cover this later in the course.
Q: What does it mean to be "human"? (what are our distinctive characteristics)
A: ?
WHAT DOES IT MEAN TO BE "HUMAN?"
BIGGER BRAIN?
HIGH EYES, COLOR BINOC.VISION?
OPPOSABLE THUMBS? TOOLS?
HABITUALLY BIPEDAL?
CULTURE?
LANGUAGE?
Natural Selection
Therefore, we will also introduce some genetic terms in this lab. (Genetics
will be covered in more detail in the textbook, lectures, and a future lab.)
The main purpose of this lab is to ensure that you learn the basic principles
of natural selection, as Darwin understood them-that is, without necessarily
understanding the genetic basis.
necessary and sufficient conditions
You will learn in this lab the three necessary and sufficient conditions for
natural selection (variation, inheritance, and differential reproductive
success) and will be introduced to different kinds of selective forces.
In addition, the other causes or factors of evolution are introduced and
discussed:
mutation, migration, and genetic drift.
Evolution
"Nothing in biology makes sense except in light of evolution
--Theodosius Dobzhansky
Sex.
Humans have a long history of careful observation of animal and plant
reproduction, and one of the first things we noticed was that, although
offspring strongly resemble their parents, they do not resemble them exactly--
offspring exhibit differences from their parents, sometimes subtle, sometimes
gross. We call this concept "descent with modification."
Evidence for organic evolution
The evidence for organic evolution comes from reproductive studies of animal
and plant breeding, from the fossil record, comparative morphology (shape and
size), biogeography (which animals live where), embryology (what stages do
developing embryos pass through, and how are they similar to embryos of other
species?), and from genetics.
Before Darwin
In the days before Charles Darwin, many enlightened biologists and philosophers
tentatively accepted the concept of organic evolution, but did not embrace it
fully because it conflicted with their system of beliefs and they lacked an
acceptable explanation of its causes.
Four causes of evolution
In section this we will concentrate on the four most important interacting
causes of organic evolution:
MUTATION,
RANDOM GENETIC DRIFT,
MIGRATION, and
NATURAL SELECTION.
1. Genotype, Phenotype, and Norm of Reaction
The genotype is the genetic constitution of an individual organism: the
blueprint by which the body is built and which directs the body's functions.
Phenotype
The phenotype includes the morphological (form and structure), physiological
(function and activities), and behavioral (acting and responding) characteristics
of that organism. There is not necessarily a one-to-one correspondence between
the genotype and phenotype. In other words, a single genotype could produce
different phenotypes in different environmental regimes.
Norm of Reaction
The term norm of reaction (referred to as "environmental variation" in your
textbook) means "the set of all phenotypic expressions possible for a given
genotype under different environmental conditions".
Examples of the Norm of Reaction
For example, humans clearly have a broad norm of reaction for body weight-
given different environmental conditions, the same person (a constant genotype)
could express wildly different body weights depending on food avaiolability.
Also, certain individual humans have higher norms of reaction for body weight
than do others.
Examples of the Norm of Reaction
Humans have a much narrower norm of reaction for body height,
and virtually no norm of reaction for number of fingers per hand or number of
hands.
2. Mutation
For our purposes, a mutation is any random change in the genetic material of
an organism that could be passed on to offspring. For this lesson, you need to
think of mutation in two ways:
1) as a cause, in and of itself, of organic evolution, and
2) as a main source of variation for the more effective cause of natural
selection to occur.
Mutation
Any mutation in the gametes (eggs or sperm) or gamete-producing cells is, by
definition, an evolutionary event, because change that can be inherited by the
offspring has taken place.
However, careful observations of the rates of single random mutations clearly
document that these rates are far too low to account for the diversity of life
forms that we currently find on our planet.
Mutation
If there were no mutation, there would be no evolution, but evolution has
proceeded at a much faster rate than mutation alone can account for.
Consequently, it is likely that random genetic dnft and natural selection play
greater roles in the evolutionary changes that take place in populations.
Evolution
In this course, we more precisely define evolution as "the change in allele
frequencies in a population over time."
Mutation, Genetic Drift, and Nat. Selection
A mutation can change a single allele.
Then random genetic drift and natural selection can take that single change and
make it into the most common allele type in a population.
Conversely, random genetic drift and natural selection can take the most common
type of allele in a population and extinguish it.
3. Random Genetic Drift and Migration
A. The term random genetic drift describes non-directed changes (i.e., changes
not directed by natural selection) in the frequencies of the alleles found in a
population.
Small population sizes provide the most likely environment for dramatic random
genetic drift to occur.
Genetic Drift
Another way to conceptualize this is to consider: if you flip a coin one
million times, the likelihood is very strong that you will come up with tails
very, very close to 50% of the time.
Genetic Drift
However, if you only flip that coin twice, you very well may not come up with a
tail at all. In a similar way, an allele may be present in high frequencies in
an original population, but if that population is reduced to two or three
individuals, it is possible that none of these remaining individuals carry
that originally prevalent allele.
Genetic Drift in small groups
Tremendous changes in the frequencies of alleles can occur when population
sizes are very low.
The Founder Effect
One situation in which random genetic drift is frequently noted is known as the
founder effect, in which a small number of individuals, perhaps just one
pregnant female, migrates to a new habitat. The genes available for the
subsequent population are based upon the specific genetic material of those
few individuals, and not on the average allele frequencies of the original
population.
The Founder effect and speciation
This founder effect is thought to be responsible for the origin of many new
species.
You may want to think of Genetic Drift as metaphorically like several groups
of people in life rafts drifting apart on the ocean.
You may want to think of Gene Flow (migration) as being like streams (people)
running together into a larger river.
B. Migration (gene flow)
Migration (Gene Flow) is an evolutionary agent in the sense that it typically
counteracts random genetic drift.
Large populations that fragment into smaller ones can maintain relative
stability of allele frequencies if individuals continually migrate between
these populations and exchange alleles (i.e., mate).
Gene flow
Migration in its own right infrequently can be an active agent of evolutionary
change.
Movement of several initially distinct groups into the same area, such as
humans from many different parts of the world arriving in North America and
interbreeding, can create allele, combinations never before present in a
species' history.
Natural selection
Much of this course focuses on the adaptation of organisms to their environment
by way of natural selection, so it will be important to understand the concepts
of natural selection, adaptation, and what we mean by the "environment."
Review: The Three conditions
A. Darwin's principle of evolution by natural selection is based upon three
necessary and sufficient conditions:
1. Variation in a trait. To understand this, you should recall the concepts
genotype and phenotype.
Genotype and Phenotype
A genotype is the underlying genetic code, and the phenotype is the physical
expression of that code.
The genotype is like the blueprints for a building as opposed to the phenotype
which is the constructed physical building.
A Trait
A trait is most simply a feature of an organism's phenotype that we choose to
call a trait. Consider two particular traits of the hair of everyone in this
class: length and color. Both vary considerably, short to long, dark to light.
Genetic inheritance: The 2nd Condition
2. Genetic inheritance. This simply means that a trait is coded for at some
level by DNA. Hair color is inherited with a certain range of norm of reaction.
Hair color can also be environmentally influenced by such things as sunlight.
Differential reproductive success
3. Differential reproductive success (RS). Darwin's insight was that if one
version of a trait causes an individual to have more offspring than "average,"
and another version does the opposite, the former will become more common in
subsequent generations, and the latter will become less common.
Obviously, there must be variation for there to be more than one version of a
trait.
Differential reproductive success
If the trait is inherited, then the underlying genetic code for that trait will
also become differentially represented in subsequent generations.
Thus, evolution happens, in such a case, via the force of natural selection.
Natural Selection
These three conditions are necessary and sufficient to result in evolution by
natural selection. Darwin published his theory of natural selection in The
Origin of Species in 1859; in 1865, a Moravian (now within the Czech Republic)
monk named Gregor Mendel published his experiments on the hybridization of peas,
founding the science of genetics.
Darwin
Darwin himself did not know of the existence of genes or chromosomes (which we
will deal with in more detail later), Condition 2 contains the requirement of
genetic inheritance.
Individuals
When we speak of individuals, we mean the individual organism, not the
individual population or species.
Natural selection acts on the level of the individual and its genotype, not at
the level of the species.
Individuals do not behave for the good of the species or group (a common
misconception), but for their own benefit.
Fitness
At this point it is important to consider the concept of "fitness." An often
misused and misunderstood phrase is "the survival of the fittest", which, by
the way, was not originally coined by Darwin.
Darwinian fitness
Darwinian fitness is a very specific, technical term, and it means the relative
frequency of an allele in future generations as a result of the properties of
that allele.
Reproductive success
On average, fitness is highly correlated with the more easily observed
"reproductive success."
Reproductive success is simply the number of fertile offspring you have that
are "normal" with respect to reproduction. (In other words, if you have a lot
of offspring that are all sterile, you don't have any reproductive success.)
Fitness and reproductive success
RS might be better measured as the number of grandchildren an individual has.
For all practical purposes, "fitness" and "RS" measure the same thing most of
the time.
Fitness in this sense does not refer to athletic ability or good health, two
traits that might or might not be inherited in a get a hair cut.
Fitness
Those individuals are most "fit" who leave the most surviving descendants to
the future.
Thus individuals who survive a long time but raise few or no offspring to
maturity have relatively low fitness, as also are those individuals with a high
rate of reproduction but a life span so short that they leave few or no
surviving offspring.
Adaptations
Natural selection is the force that shapes adaptations (in fact, the best
possible definition of an "adaptation" is a trait that was shaped by natural
selection). One can think of natural selection as the verb, and an adaptation
as the noun: A proper, biological adaptation is a trait that is inherited (it
is genetic), and is likely to increase its bearer's fitness (or, among several
bearers, will increase average fitness).
Environmental change
However, environments rarely stay constant for very long, and thus the fitness
advantages of a particular adaptation may change. A warm furry coat that
evolved in a species during a cold millennium may be a disadvantage if climate
warms.
Since what is adaptive for an organism may be constantly shifting, so may
natural selection and its effects be acting differently in a given lineage
over time.
Global climatic change
Not only is there fairly regular global climatic change affecting the organism's
environment, but other important things change as well, including the types,
diversity, and numbers of prey or vegetation on which an organism may feed,
or predators that; may feed on it, and so on.
Artificial selection
B. In his research leading up to The Origin of Species, Darwin spent many years
carefully observing his neighbors in the palatial English countryside, who were
unwittingly engaged in experiments in artificial selection, especially pigeon
breeding, and these served as the inspiration for his idea of natural selection
(Darwin himself was an avid breeder of pigeons.)
Artificial selection
Artificial selection simply refers to a subset of natural selection in which
humans are the agents determining the differential reproductive success. It is
pnmarily used to produce certain desired traits in livestock and crops.
Non-beneficial behaviors
Darwin also noticed in his research that many organisms in nature possessed
organs or performed behaviors that did not seem beneficial for their survival;
for example, the oversized antlers of some deer and the extravagant plumage of
some birds seem to be deleterious traits because the antlers burden the deers'
movements and the plumage of the birds attracts predators.
Sexual selection
He reconciled these traits with his theory of natural selection by proposing
the ancillary idea of sexual selection, which results from the struggle between
members of one sex, most often by 1) male-male competition or 2) female choice,
to mate with the other sex.
Sex vs survival
There is a trade-off in these organisms between their need to survive and their
need to reproduce.
Sexual selection
Sexual selection, as one would expect, is a fascinating and complicated process
with many subtleties and nuances that are only just being unraveled by
scientists.
For our present purposes, note that sexual selection results in most of the
differences in size, physical details, and behaviors between males and females.
Modes of Selection
When a morphological trait exhibits a continuous distnbution, e.g., height or
weight, we can characterize the patterns that result from an episode of natural
selection in three ways:
stabilizing selection,
directional selection, and
disruptive selection.
Stabilizing selection
Stabilizing selection decreases the frequency of traits on the extreme end of
their range of variation. It serves to increase the frequency of individuals
with the average value of a given trait (see Fig. 1). It occurs when the
extreme values of a trait (the tallest and the shortest, the lightest and the
darkest, etc.) are less fit than the average values.
An example
An example might be wing length in birds. Long wings are good for efficient
flight, but birds with long wings cannot maneuver easily, and so are caught
by predators. Short wings are good for quick turns, but birds with very short
wings spend too much energy on flight and cannot forage efficiently.
An example
A particular species of bird, due to the environmental context in which it
lives, may have an optimal wing size. Despite the continuous introduction (in
a population over time) of mutations for longer or shorter wings, the optimal
length remains the most common, with too-short or too-long versions selected
against.
Directional Selection
Directional selection changes the average value of a trait over time. The
result is that a new value, either higher or lower than the original one,
becomes the average for the trait in that population. This mode of selection
has a visible effect on a population over time, causing a trait to change in a
particular direction.
An example
Let's take the same bird from the example above, and remove the predators from
its environment. In the absence of selection against long wings, the individual
birds with longish wings might forage more efficiently than the average bird in
this population.
An example of Directional Selection
Such individuals may leave more offspring than the average bird, especially in
years when the food supply is short. In this way, the population may change
over time to become a long-win~ed form in comparison to the ancestral
population.
Disruptive selection
Disruptive selection occurs when individuals possessing the most common value
of a trait are selected against, with the result that individuals at the
extreme ends of the distribution of a trait have relatively greater fitness,
and thus increase in relative frequency.
An example
Imagine a rodent population with variable, but generally grayish, coat color,
that lives in a heavily vegetated environment- Now introduce climate change,
so that the vegetation becomes rare, but somehow this rodent survives. The
denuded landscap~ consists of open areas of white sand interspersed with piles
of very dark-colored boulders that cast heavy shadows.
An example
The gray form of rodent would be visible to predators on the sand, or on the
dark rocks.
If the light-colored forms could learn to forage in the open, where they are
better camouflaged against the light sand, and darker-colored forms foraged
among the rocks, then they may individually have an advantage with respect to
predation.
An example
Intermediate forms would do poorly in all contexts, and owing to increased
predation, would be less fit. Eventually, the ancestral population may split
into two different forms--possibly two different species--one white, the other
black.
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Lab 1 Notes Fall 1997
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