Table of Contents
Evolution In A
Nutshell
As an evolutionist, have you ever really considered the process as a "whole"? Well, have ya?
The following was taken from mostly evolutionary sources. And, of course, it has the legendary BF editorial quips peppered throughout.
In the beginning...
Physical matter is the only ultimate reality - everything in
the cosmos, including life, can be explained in terms of interacting
matter.
Some 10 to 20 billion years ago, all of the matter and energy of the universe was compressed into a cosmic egg or plasma ball the size of a period on this page and consisting of sub-atomic particles and radiation.
Nobody knows where the cosmic egg came from, or how it got there -- it was just there.
For some equally inexplicable reason, it spun around extremely fast until KABOOOM! It exploded.
Instantaneously and randomly, enough energy was created from somewhere to break the gravitational bond which held this massive body together in the first place, exploding the super-heated particles throughout space.
As the matter and radiation expanded it cooled sufficiently for elements to form, as protons and electrons combined to form hydrogen, and neutrons were subsequently captured to form helium.
These gases expanded radially in all directions throughout the universe until they were so highly dispersed that an extremely low vacuum and temperature existed.
No oxygen, nitrogen, phosphorus, carbon, sulfur, copper, iron, nickel, uranium, or other elements existed at this time.
Then somehow the molecules of gas that were racing out at an enormous speed in a radial direction began to collapse in on themselves in local areas by some gravitational attraction from some newly formed mass(es).
The molecules within a space of about six trillion miles diameter collapsed to form each star, a hundred billion stars somehow collected to form each of the estimated 100 billion galaxies in the universe, and our own solar system formed about five billion years or so ago from a cloud of dust and gas made up of the exploded remnants of previously existing stars.
So . . . supposedly the universe was formed with no outside influence or cause - which makes for one whopper of a "virgin-birth" story!
Sun's formation
More time passes and the atoms became more abundant in the universe.
They began to pull together through atomic forces and the gravitational
force (probably not the same gravitational force that held it
all together as a singularity in the first place).
Gaseous bodies became more massive, which attracted more atoms and became more massive. The gravitational force of these early bodies were so great that they collapsed in on themselves, which began fusion.
Hydrogen atoms combined, yielding larger atoms and enormous amounts of energy; enough energy to keep these stars from collapsing any more. Eventually, the fusion process has to end and the star will explode, sending out more massive atoms into the universe - maybe to repeat the whole process all over again.
Over time, these atoms collect and combine to create planets, smaller stars, asteroids, and numerous other solid bodies in space - the final frontier.
Formation of the Milky Way Galaxy
Early in our universe, as
matter was quickly expanding outwards, clusters of gigantic amounts
of matter stopped quickly expanding and began orbiting in a circular
motion around a common center of mass.
These became early galaxies, which would grow in size from such things as collisions with other galaxies.
Formation of the Solar System
The solar system was born about 4.5 billion years ago, when something
disturbed and compressed a vast cloud of cold gas and dust --
the raw material of stars and planets. The disturbance may have
been a collision with another cloud, or a shock wave from an
exploding star.
Whatever the cause, the cloud fragmented into smaller, denser pockets of matter, which collapsed inward under the pull of gravity. In perhaps 100,000 years, one of the pockets, called a nebula, condensed into a volume about the size of the present-day solar system.
Earth's formation
The Earth was formed from the collapse of a star. Earth
was a relatively cold, homogeneous agglomerate of planetary particles
and planetismals.
Earth's first atmospheric conditions were dramatically different from those that exist today. It had no oxygen, but contained certain necessary ingredients, including ammonia, nitrogen, hydrogen, water vapor and methane.
Heating of the Earth by compression under its own weight, collision with other impactors, and radioactive decay lead to differentiation- the formation of layers with distinct densities and chemical compositions: the core, mantle and crust.
Then first permanent crust formed on Earth. Degassing of minerals within the Earth's interior through volcanism (volcanos - not pointy eared aliens) produced the waters of the oceans and atmosphere.
The Moon
Probably formed a bit later, when a body several times as massive
as Mars slammed into our planet. The collision blasted a geyser
of hot gas and molten rock into orbit around Earth; the material
quickly cooled and coalesced to form the Moon.
(Or maybe, similar to the big bang, there was no outside force but rather an inner one that exploded the gas out into space).
Life arises
Originally, the earth had no atmosphere. Due to gravity, the
earth became more and more compressed, causing heat and pressure
to build up until volcanoes erupted all over the earth. When
the lava hardened and the gases cooled, it rained.
At this point, the earth's surface was not protected from the sun's deadly ultraviolet rays as in the case of bodies of water. Underwater, small unicellular organisms formed, developed and grew.
Life spontaneously generated, by chance, on this planet's ancient water supply (water which contained absolutely no life, just minerals and chemical substances which are used by living things) from inanimate matter through the interaction of matter and energy - though this is not observed today.
(Note: Life may have spontaneously generated on some other planet's surface and somehow have been transported here from another planet millions of light years away via star dust, meteors, comets, or spaceships - somehow surviving very very long in space despite cosmic rays and other life-killing radiation. This process is known as "panspermia".)
Four and a half billion years ago the young planet Earth was almost completely engulfed by the shallow primordial seas. Powerful winds gathered random molecules from the atmosphere. Some were deposited in the seas.
Tides and currents swept the molecules together which then interacted with solar energy. And somewhere in this ancient ocean life began.
Just like in 'Frankenstein,' a bolt of energy (maybe lightening) into the primeval mix of chemicals jumpstarted life (because it is well known that just mixing these ingredients does not create life).
(Note: It also is theorized that life may have begun in clay because the "clay-life" explanation explains several problems not explained by the "primordial soup" theory. Life on earth must have began from clay rather than in the the warm little pond as proposed by Darwin.
The clay-life theory holds that an accumulation of chemicals produced in clay by the sun eventually led to the hypothetical self-replicating molecules that evolved into cells and then eventually into all life forms on earth today.)
Againts all odds (10 to the 67th power to 1 against even a small "protein" forming by time and chance, in an ideal mixture of chemicals, in an ideal atmosphere, and given up to 100 billion years - an age 10 to 20 times greater than the supposed age of the Earth) a small protein arose.
Then another. And another. And so on. And so on.
Mathematicians generally agree that, statistically, any odds beyond 1 in 10 to the 50th have a zero probability of ever happening - but it happened anyway.
An origin of life, anywhere, consists of the chance arising of a self-replicating entity. Nowadays, the replicator that matters on Earth is the DNA molecule, but the original replicator probably was not DNA.
We don't know what it was. The original self-duplicating entities must have been simple enough to arise by the spontaneous accidents of chemistry and energy.
But something produce DNA in these packages of matter although only previous DNA produces DNA these days, but it happened none-the-less. (DNA is somewhat like a computer program on a disk, which is programmed by a programmer. It stores and transfers encoded information and instructions.)
Certain simple molecules underwent spontaneous, random chemical reactions until after about half-a-billion years complex organic molecules were produced.
Molecules that could replicate (make copies of themselves) eventually were formed (the most common guess is nucleic acid molecules), along with enzymes and nutrient molecules that were surrounded by membraned cells.
The first organized form of primitive life was a tiny protozoan (a one-celled animal). Millions of protozoa populated the ancient seas.
These early organisms were completely self-sufficient in their sea-world. They moved about their aquatic environment feeding on bacteria and other organisms. From these one-celled organisms evolved all life on earth - including you.
There was once a time when none of the creatures in the world had lungs (i.e. fish). This means that there was no genetic information (the 'blueprint' for living things, carried on the molecule DNA) for lungs - anywhere.
Then, at a later time, 'lung information' arose and was added to the world (i.e. killer whales and cute dolphins and even lungfishies), but no 'feather information' as yet - feathers evolved later (i.e. birds).
These processes acted for many tens of millions of years, most likely hundreds of millions of years, before true cellular life was brought into being - again, against all odds (less than 1 chance in 10 to the 40,000th power that life could have originated by random trials. (10 to the 40,000th power is a 1 with 40,000 zeros after it).
Reproduction
The ultimate fate of a cell or any living thing is death and
destruction. No dynamically functioning unit therefore can survive
as a species without self-reproduction. The ability to reproduce,
however, would have had to exist from the very beginning in any
system, no matter how simple or complex, that could have given
rise eventually to a living thing.
The first life forms were simple celled creatures which divided themselves to reproduce (known as 'asexual' reproduction).
Cells eventually somehow "learned" how to duplicate themselves by copying a DNA molecule (which contains a complete set of instructions for building a next generation of cells). During the reproduction process, mutations changed the DNA code and produced cells that differed from the originals.
These asexual organisms then formed both male and female sex organs for some reason and mated producing similar creatures which eventually didn't asexually divide, but rather only mated to produce offspring.
The variety of cells generated by this process eventually developed the machinery required to do all that was necessary to survive, reproduce, and create the next generation of cells in their likeness.
Those clumps of cells that were better able to survive became more numerous in the population.
Life Evolves
All species of organisms originate through the process of biological
evolution. In this process, new and more complex species arise
from a series of natural changes.
The mechanism for evolutionary change resides in genes-the basic units of heredity. Genes affect how the body and behavior of an organism develop during its life.
The information contained in genes can change-a process known as mutation. The way particular genes are expressed-how they affect the body or behavior of an organism-can also change.
Over time, genetic mutations can alter a species's overall way of life, such as what it eats, how it grows, and where it can live - though new information arising has yet to be observed. But you gotta have faith, we will observe it eventually.
Even though no new information is produced, genetic mutations can improve the ability of organisms to survive, reproduce, and, in animals, raise offspring. This process is called adaptation.
Parents pass adaptive genetic mutations to their offspring, and ultimately these changes become common throughout a population-a group of organisms of the same species that share a particular local habitat.
Many factors can favor new adaptations, but changes in the environment often play a role.
For clarity we must restrict this process to meaningful change, especially the descent of new types and more complex of organisms from earlier less complex and different ones.
Evolution implies "descent from a common ancestor" with all of life related, consisting of modified forms of very different things, such as a person descending from a fish.
Evolution does not mean merely "change," for all things change with time.
Once multicellular organisation became possible as atmospheric oxygen levels rose, the early multicellular organisms rapidly diverged into many adaptive forms.
Mass extinction events, natural
selection and and an organism's unique adaptations via genetic
mutations mark the history of evolution - and you.
Living orders of placental mammals, be it bats, humanity, whales
or camels, have as their common ancestor a small insectivore
creature that went through a major phase of adaptive radiation.
Plants
Approximately 410 million years ago, the oxygen in the atmosphere
had reached levels greater than 2 percent and produced a by-product
of its own: ozone.
This blanket of gas was enough to protect plants from the sun's UV (ultra violet) rays and created a hospitable environment for organisms headed for land - "Land Ho!".
Also, due to the tides, water levels would rise and fall and mud flats started to occur in more shallow areas. Sometimes they would be dry and at other times they would be wet creating ideal grounds for the development of land plants.
Water-dwelling plants had large surface-to-volume ratios. They were supported by water and had a thin construction for easy transfer and diffusion of gases and minerals throughout their entire surface.
Now aquatic plants required a new construction more suitable for habitation on land for some reason. Once on land, some of the green algae developed ways to adapt to their new environment.
Through natural selection, plants became more rigid in order to support themselves out of water. They also developed a more compact shape and stronger cell walls with hard outer layers to protect them from losing moisture and suffering from the other drying effects of the wind.
In order to continue breathing, they developed small openings called stomata. Plants also began to absorb water and minerals in specific places rather than using their entire surface for that function.
Vascular plants were the result of further adaptations that occurred due to the need for plants to transport food, water and minerals from areas of plenty or production to areas of need.
Xylem tissue for transporting water and minerals, and phloem tissues for transporting food were developed. Plants could now grow larger than before.
They also became even more rigid in order to grow upward, so they could better compete for sunlight to be used in photosynthesis.
During the course of evolution plant and animal groups have interacted to one another's advantage. For example, as flowering plants have become less dependent on wind for pollination, a great variety of insects have emerged as specialists in transporting pollen.
The colors and fragrances of flowers have evolved as adaptations to attract insects who coincidently liked what the plants were procucing.
Fish
Fish are the first known vertebrates and also the stepping stone
to all land-walking vertebrates. They began as jawless, bottom
feeders and evolved into sharks, rays, tunas, and many extinct
species.
The first fish to evolve were the Agnathans. These jawless fishes are the first vertebrates and have round mouth parts that could be used for sucking or filter feeding.
These rasping, sucking mouths are currently found on modern lampreys and hagfishes.
These fish were often extremely armored in order to help them protect themselves.
Most of these types of fish are currently extinct with the exceptions of the lampreys and the hagfish which seem to not have evolved.
From these bottom feeding, jawless fish came the evolution of jawed fish. Jaws evolved only once (rather than evolving multiple times in different species through parallel evolution).
Jaws evolved from gill arches which are the bony parts between gill slits.
It is thought that a gill arch in an agnathan became fused to its skull. The upper part of the gill support became the top jaw and the bottom part of the gill support became the bottom jaw.
The evolution of the jaw is incredibly important because it led to fish to be able to ingest a much wider variety of foods and allowed them to be active hunters as opposed to passive filter feeder. This led to a wide variety of adaptations in morphology.
Fish became more agile to be better predators, they were able to reduce their armor because they were less vulnerable, and their muscle density was able to decrease becuase they no longer led such a sluggish lifestyle.
Placoderms (early jawed fish) had bony armor that covered the head and forepart of the body. In many, a movable joint between the head and body armor let the head rock back to open the mouth wide.
The primitive jaws had jagged bony edges that served as teeth.
The tail end usually lacked protection.
The Dunkleosteus, a placoderm, grew to be as large as 35 feet, had well developed jaws, with fang like teeth. The front of the trunk was heavily armored and the hind part was either bare or covered with small scales (11). The Dunkleosteus and all the other large placoderms are extinct, but in the Devonian they dominated both salt and freshwater.
Sharks, skates, and rays (along with some other fish) and these first evolved between 400 and 450 million years ago. This class is commonly refer to as the cartilaginous fish because they lack true bone, instead they have cartilage and calcified cartilage for internal support. This type of skeleton is extremely light and flexible and helps these species be agile predators.
The bony fish, while being varied, all share an extremely important characteristic: a swim bladder. This probably evolved from lungs which had appeared in some freshwater species.
The swim bladder is a internal structure which allows bony fish to float easily at any water level.
There is still much controversy about the exact steps of evolution from lobe-finned fish to walking, land living, vertebrates (in the form of amphibians). There was originally much controversy over whether the limbs of tetrapods (limbed vertebrates) evolved in water or on land as an emergency feature.
Perhaps early lung fishes in times of drought had used their fleshy fins to pull themselves from a pond that was trying onto land to search for a more fruitful water source. The fish that made this journey successfully were able to reproduce and their offspring began to have modified limbs which were able to allow them to move from water source to water source and eventually these developed into true limbs.
Or maybe the Devonian was so conducive to fish that the were able to have many offspring survive and that these were drawn to the land with its not yet exploited food sources.
Or yet still, the earliest tetrapods evolved limbs to help maneuver through the Devonian habitat which consisted of very dense wetlands. These creatures could maneuver through these dense branches and plants by using their limbs rather than just having to "wiggle" through.
They could also use the limbs to anchor themselves to wait silently for prey and then use their water adaptations to snag prey deftly.
These huge tetrapods may have began to use land in a very gradual fashion, for breeding or to escape predators.
Neverthless, it (fish migrating to land) happened - one way, or another, or another. They then became amphibians [from Greek words meaning 'double life'] whose modern decendants include frogs, toads, and salamanders."
Amphibians
From one of the many groups of fish inhabiting pools and swamps
emerged the first land vertebrates, starting the vertebrates
on their conquest of all available terrestrial habitats just
as the plants did earlier.
Prominent among the numerous aquatic forms were the lobe-finned fish that possessed the ability to gulp air when they rose to the surface. These ancient air-breathing fish represent the stock from which the first land vertebrates, the amphibians, were derived.
The ones that migrated onto land were only crudely adapted for terrestrial existence, but because they did not encounter competitors, they survived.
Lobe-finned fish did, however, possess certain characteristics that served them well in their new environment, including primitive membranous lungs and internal nostrils, both of which are essential for atmospheric breathing.
Such characteristics, called preadaptations, did not develop because they were preparing to migrate to the land; they were already present by accident and became selected traits only when they imparted an advantage to the fish on land.
How terribly lucky for them.
The ancient amphibians never became completely adapted for existence on land for some strange reason, however.
They spent much of their lives in the water, and their modern descendants--the salamanders, newts, frogs, and toads--still must return to water to deposit their eggs.
The elimination of a water-dwelling stage, which was achieved by the reptiles, represented a major evolutionary advance.
Land Dwellers
The first animal life to reach the land were various
members of the phylum 'Arthropoda' spiders, scorpions, and primitive
insects.
The fish-to-four-legs transition occurred about 370 million years ago. They are the ancestors of all tetrapods -- from dinosaurs to dogs, horses to humans.
It was long thought that the first tetrapods were fish that first clambered ashore, then evolved limbs to stand on. One theory held that tetrapods arose from fish living in ponds that dried up periodically. When a pond evaporated, these fish used their fins to drag themselves to new ponds.
Recent discoveries, however, reveal that fish evolved limbs first, then came ashore.
Careful study of fossil anatomy shows that those rudimentary limbs could not support their owner's weight. Rather they were used to support the animal in the shallow swamp edges in which it lived.
Those early tetrapods evolved from the so-called lobe-finned fishes, a group of fish that had stout, strong fins whose bones foreshadowed in basic arrangement those of arms and legs.
About 300 million years ago, certain amphibia strangely developed an egg that was surrounded by a protective shell of thin limestone. The shell was permeable to air, but not to water. Air could reach the developing embryo inside, but water could not leave it.
Reptiles
Perhaps the most important factor contributing to the emergence
of reptiles from the amphibians was the development of a shell-covered
amniotic egg that could be laid on land.
This development enabled the reptiles to spread throughout the Earth's landmasses.
Like the eggs of birds, which developed later, reptile eggs contain a complex series of membranes that protect and nourish the embryo and help it breathe.
The reptiles, and in particular the dinosaurs, endured as the dominant land animals of the Earth for well over 100 million years.
The first dinosaurs appear during the Triassic Period [248-208 million], along with some of the first mammals, but the dominant animals at the beginning of this epoch are reptiles like turtles and 'fish lizards' called ichthyosaurs.
Dinosaurs
The largest abrupt event of the last 100 million years
occurred when a meteor hit the region of Yucatan causing mass
extinction about 65 million years ago, triggering the extinction
of the dinosaurs and beginning the reign of mammals.
Then, ten million years later, a warm spell led to significant global warming, with Palm trees in Alaska and crocodiles in the Arctic.
Dinosaurs dominated the land fauna during the Jurassic Period.
The dinosaurs all died out in a comparatively short period, about 65 million years ago, as did other giant reptiles and many other types of organisms.
The reptilian dynasty collapsed before the close of the Mesozoic Era. Relatively few of the myriad Mesozoic reptiles have survived to modern times; those remaining include the CROCODILE, LIZARD, SNAKE, and TURTLE.
Birds
Birds descend from ground-dwelling, meat-eating dinosaurs of
the group known as theropods. Birds are not only descended from
dinosaurs, they are dinosaurs (and reptiles).
The birdlike characteristics of the theropods that evolved prior to birds did not appear all at once, and some were present before the theropods themselves emerged in the earliest dinosaurs.
Feathers:
Just like some birds select their breeding pair through ritualistic displays, the same way some dinosaurs were able to select their mates millions of years ago.
Some male dinosaurs showed and displayed their colorful scale like skin to the females for the purpose of mating, until one day through mutations some dinosaurs within a specie began showing very colorful shiny scale like skin in some parts of the body, such as near the neck, on top of their heads and other places.
Their skin was shiny for it had little ripples that when the light shined on them, it looked a bit metallic just like some birds feathers reflect the light in the same manner.
This attracted the female dinosaurs into mating with these individuals more than the others, therefore, improving the quality of this genetic trait, until these ripples eventually became tiny slender furry like scales within their scale like skin.
Time went by, and these scales became more and more furry such as the feathers we know today, but very short.
Some dinosaurs had them on their heads, and some on their arms, until through ritualistic selection some female dinosaurs began liking the mutations of longer dinosaur feathers, especially around the arms and on top of the heads of the males.
Time passed by, as better feathers created a more complex display of rituals which demanded more better feathers, which were better looking and better arranged.
The dinosaurs who have these feathers on their arms, cornered their females as they flashed their beautiful colorful feathers at them flapping their arms up, then down again. So the dinosaurs who had the most beautiful feathers in the best displayed order, where the ones that mated.
Time went by and some of these dinosaurs now had feathers all over their arms and tail.
Flight:
The immediate reptilian ancestor of dinosaurs was already bipedal and upright in its stance (that is, it basically walked like a bird), and it was small and carnivorous.
Its hands, in common with those of early birds, were free for grasping (although the hand still had five digits, not the three found in all but the most basal theropods and in birds). Also, the second finger was longest-not the third, as in other reptiles.
In the ancestors of dinosaurs, the ankle joint had already become hingelike, and the foot bones had became elongated. The ankles were held off the ground, so the immediate relatives of dinosaurs, and dinosaurs themselves, walked on their toes and put one foot in front of the other, instead of sprawling.
Many of the changes in the feet increased stride length and running speed, a property that would one day help avian theropods to fly.
The earliest theropods had hollow bones and cavities in the skull; these adjustments lightened the skeleton. They also had a long neck and held their back horizontally, as birds do today.
In the hand, digits four and five (the equivalent of the pinky and its neighbor) were already reduced in the first dinosaurs; the fifth finger was virtually gone. Soon it was completely lost, and the fourth was reduced to a nubbin.
Those reduced fingers disappeared altogether in tetanuran theropods, and the remaining three (I, II, III) became fused together sometime after Archaeopteryx evolved.
In the first theropods, the hind limbs became more birdlike as well. They were long; the thigh was shorter than the shin, and the fibula, the bone to the side of the shinbone, was reduced.
These dinosaurs walked on the three middle toes-the same ones modern birds use. The fifth toe was shortened and tapered, with no joints, and the first toe included a shortened metatarsal (with a small joint and a claw) that projected from the side of the second toe.
The first toe was held higher than the others and had no apparent function, but it was later put to good use in birds.
By the time Archaeopteryx appeared, that toe had rotated to lie behind the others. In later birds, it descended to become opposable to the others and eventually formed an important part of the perching foot.
Major changes occurred in the forelimb and shoulder girdle; these adjustments at first helped theropods to capture prey and later promoted flight.
During theropod evolution the arms became progressively longer, except in some giant carnivores in which the forelimbs were relatively small. The forelimb was about half the length of the hind limb in very early theropods.
By the time Archaeopteryx appeared, the forelimb was longer than the hind limb, and it grew still more in later birds. This lengthening in the birds allowed a stronger flight stroke.
The hand became longer, too, accounting for a progressively greater proportion of the forelimb, and the wrist underwent dramatic revision in shape.
Basal theropods possessed a flat wristbone that overlapped the bases of the first and second palm bones and fingers. In maniraptorans, though, this bone assumed a half-moon shape along the surface that contacted the arm bones.
The halfmoon shape was very important because it allowed these animals to flex the wrist sideways in addition to up and down. They could thus fold the long hand, almost as living birds do.
The longer hand could then be rotated and whipped forward suddenly to snatch prey.
In the shoulder girdle of early theropods shoulder blade was long and straplike; the coracoid (which along with the scapula forms the shoulder joint) was rounded, and two separate, S-shaped clavicles connected the shoulder to the sternum, or breastbone.
The scapula soon became longer and narrower; the coracoid also thinned and elongated, stretching toward the breastbone.
The clavicles fused at the midline and broadened to form a boomerang-shaped wishbone. The sternum, which consisted originally of cartilage, calcified into two fused bony plates in tetanurans.
Together these changes strengthened the skeleton; later this strengthening was used to reinforce the flight apparatus and support the flight muscles.
The new wishbone, for instance, probably became an anchor for the muscles that moved the forelimbs, at first during foraging and then during flight.
In the pelvis, more vertebrae were added to the hip girdle, and the pubic bone (the pelvic bone that is attached in front of and below the hip socket) changed its orientation.
Finally, the tail gradually became shorter and stiffer throughout theropod history, serving more and more as a balancing organ during running, somewhat as it does in today's roadrunners.
This transition in tail structure paralleled another change in function: the tail became less and less an anchor for the leg muscles. The pelvis took over that function, and the muscle that once drew back the leg now mainly controlled the tail.
In birds that followed Archaeopteryx, these muscles would be used to adjust the feathered tail as needed in flight.
Feathers also became of some good use to some dinosaurs who needed to escape their predators, for some of them found out that by putting their arms to the side in an aerodynamic horizontal manner and then flapping them to the back in a vertical manner they could give themselves a little push and give less stress to their running legs while being chased.
Also they were able to change directions much faster while running by putting the left arm to the side in a vertical manner to make a fast left or the right arm to the side in a vertical manner to make a fast right, which gave them an even bigger edge at escaping their predators.
This was the magor adaptation that made dinosaurs into flying birds, for the better the designs that these feathers became to help these dinosaurs escape their predators and the more skillful these dinosaurs became at using those feathers, the more these dinosaurs began to leave the ground, until one day some dinosaurs although were not able to fly for long distances, they were able to make high long jumps, such as the way chickens do today, and escape their predators.
After that, some of these dinosaurs became aware that by flying short distances, they were able to jump on top of trees to escape their predators and were also able to get food and seeds which they could not reach before.
Or maybe they started up in the trees, and flew down, and so scales grew longer and longer somehow and promoted gliding.
Whichever.
Mammals
The decline of the reptiles provided evolutionary opportunities
for birds and mammals. Small and inconspicuous during the Mesozoic
Era, mammals rose to unquestionable dominance during the Cenozoic
Era (beginning 65 million years ago).
Mammals, including humans, are descended from animals that reproduced by means of externally laid eggs that were rich in yolk.
By about 220 million years ago, reptiles had evolved into animals that had differientated teeth, as we do; that had hair; that were warm blooded; that laid eggs containing partially developed embryos [and eventually went on to develop mechanisms for giving birth to the embryos themselves]; and that produced milk to feed their young.
About 100 million years ago, some mammals, for no particular reason, improved the child-bearing system and made it more complex. The embryo remained within the mother's body, nourished by a placenta.
The Cenozoic Era is truly the Age of Mammals. At its beginning, the world is without any larger-sized terrestrial mammals. The next 65 million years brings marine mammals, as well as the land mammals, including Homo sapiens, that we know today - including you.
Mammals and subsequently humanity may not have become dominant on earth had it not been for the global catastrophe that led to the extinction of the dinosaurs 65 million years ago.
Marine Mammals
Dolphins and whales are also tetrapods, having evolved from a
race of wolflike creatures that began to adapt themselves to
water about 50 million years ago.
Their nostrils merged together and moved to the top of their head to form "blow holes". And their arms/legs devolved back into flippers.
Man
Humans are creatures whose roots lie in the animals (we
are first animals, then mammals, then primates). Accordingly,
we find ourselves at the tip of a branch of an immense tree of
life (and death), a tree that has been developing and growing
ever more diverse over a period of four billion years.
Ancestral human species adapted to new environments as their genes changed, altering their anatomy (physical body structure), physiology (bodily functions, such as digestion), and behavior.
Over long periods, evolution dramatically transformed humans and their ways of life.
Adaptations to a specific diet in our ancestors paved the way for the development of modern humans.
Humans and the so-called great apes (large apes) of Africa-chimpanzees (including bonobos, or so-called pygmy chimpanzees) and gorillas-share a common ancestor that lived sometime between 8 million and 5 million years ago.
Primates, the order of mammals to which humans belong, underwent adaptive radiation (they spread out).
Part of human radiation is an adaptation to life on the ground. Ground living forms need to range farther to find food and survive and form fewer varieties than tree-living forms.
Ground-living is a very ancient adaptation on the evolutionary line leading to humanity as the oldest hominids walked upright on adapted feet. Our upright stance evolved at least 3.6 million years ago, before any significant brain enlargement evolved.
Walking upright probably occured as these ancestors stood up for long periods of time looking over tall grass scanning for aproaching predators and/or reaching for food in the trees from which they came down out of.
Between 6 million and 2 million years ago in Africa, a number of different species lived that were bipedal (and hence hominids) but still had small brains and protruding faces.
The earliest hominids lived in the woodlands and forests, and only later moved out into the open grasslands (savanna).
Over time, the teeth became less apelike, including the reduction in the size of the canines. As some teeth got smaller, the brain got bigger and more complex, therefore smarter.
And that's how YOU came to be.
What's the matter?
Couldn't swallow that?!
If you would like to read the "nutshell" version of Biblical history, migrate here.