Understanding evolution

[Elaine Friedland]

http://www.newsweek.com/id/216140
Newsweek Print This
Evolution
By Richard Dawkins | NEWSWEEK

Published Sep 25, 2009

From the magazine issue dated Oct 5, 2009

Creationists are deeply enamored of the fossil record, because they have been taught (by each other) to repeat, over and over, the mantra that it is full of "gaps": "Show me your 'intermediates!' " They fondly (very fondly) imagine that these "gaps" are an embarrassment to evolutionists. Actually, we are lucky to have any fossils at all, let alone the massive numbers that we now do have to document evolutionary history—large numbers of which, by any standards, constitute beautiful "intermediates." We don't need fossils in order to demonstrate that evolution is a fact. The evidence for evolution would be entirely secure even if not a single corpse had ever fossilized. It is a bonus that we do actually have rich seams of fossils to mine, and more are discovered every day. The fossil evidence for evolution in many major animal groups is wonderfully strong. Nevertheless there are, of course, gaps, and creationists love them obsessively.

Let's use the analogy of a detective coming to the scene of a crime where there were no eyewitnesses. The baronet has been shot. Fingerprints, footprints, DNA from a sweat stain on the pistol, and a strong motive, all point toward the butler. It's pretty much an open-and-shut case, and the jury and everybody in the court is convinced that the butler did it. But a last-minute piece of evidence is discovered, in the nick of time before the jury retires to consider what had seemed to be their inevitable verdict of guilty: somebody remembers that the baronet had installed spy cameras against burglars. With bated breath, the court watches the films. One of them shows the butler in the act of opening the drawer in his pantry, taking out a pistol, loading it, and creeping stealthily out of the room with a malevolent gleam in his eye. You might think that this solidifies the case against the butler even further. Mark the sequel, however. The butler's defense lawyer astutely points out that there was no spy camera in the library where the murder took place, and no spy camera in the corridor leading from the butler's pantry. "There's a gap in the video record! We don't know what happened after the butler left the pantry. There is clearly insufficient evidence to convict my client."

In vain, the prosecution lawyer points out that there was a second camera in the billiard room, and this shows, through the open door, the butler, gun at the ready, creeping on tiptoe along the passage toward the library. Surely this plugs the gap in the video record? But no. Triumphantly the defense lawyer plays his ace. "We don't know what happened before or after the butler passed the open door of the billiard room. There are now two gaps in the video record. Ladies and gentlemen of the jury, my case rests. There is now even less evidence against my client than there was before."

The fossil record, like the spy camera in the murder story, is a bonus, something that we had no right to expect as a matter of entitlement. There is already more than enough evidence to convict the butler without the spy camera, and the jury was about to deliver a guilty verdict before the spy camera was discovered. Similarly, there is more than enough evidence for the fact of evolution in the comparative study of modern species and their geographical distribution. We don't need fossils. The case for evolution is watertight without them, so it is paradoxical to use gaps in the fossil record as though they were evidence against evolution. We are lucky to have fossils at all.

What would be evidence against evolution, and very strong evidence at that, would be the discovery of even a single fossil in the wrong geological stratum. As J.B.S. Haldane famously retorted when asked to name an observation that would disprove the theory of evolution, "Fossil rabbits in the Precambrian!" No such rabbits, no authentically anachronistic fossils of any kind, have ever been found. All the fossils that we have, and there are very very many indeed, occur, without a single authenticated exception, in the right temporal sequence. Yes, there are gaps where there are no fossils at all, and that is only to be expected. But not a single solitary fossil has ever been found before it could have evolved. That is a very telling fact. A good theory is one that is vulnerable to disproof, yet is not disproved. Evolution could so easily be disproved if just a single fossil turned up in the wrong date order. Evolution has passed this test with flying colors. Skeptics of evolution who wish to prove their case should be diligently scrabbling around in the rocks, desperately trying to find anachronistic fossils. Maybe they'll find one. Want a bet?

The biggest gap, and the one the creationists like best of all, is the one that preceded the so-called Cambrian Explosion. A little more than half a billion years ago, in the Cambrian era, most of the great animal phyla "suddenly" appear in the fossil record. Suddenly, that is, in the sense that no fossils of these animal groups are known in rocks older than the Cambrian, not suddenly in the sense of instantaneously; the period we are talking about covers about 20 million years. Anyway, it is still quite sudden, and, as I wrote in a previous book, the Cambrian shows us a substantial number of major animal phyla "already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history. Needless to say, this appearance of sudden planting has delighted creationists."

The last sentence shows that I was savvy enough to realize that creationists would like the Cambrian Explosion. I was not (back in 1986) savvy enough to realize that they'd gleefully quote my lines back at me in their own favor, carefully omitting my careful words of explanation. On a whim, I just searched the World Wide Web for "It is as though they were just planted there, without any evolutionary history" and obtained no fewer than 1,250 hits. As a crude control test of the hypothesis that the majority of these hits represent creationist quote—minings, I tried searching, as a comparison, the clause that immediately follows the above quotation: "Evolutionists of all stripes believe, however, that this really does represent a very large gap in the fossil record." I obtained a grand total of 63 hits, compared to the 1,250 hits for the previous sentence.

I have dealt with the Cambrian Explosion at length before. Here I'll add just one new point, illustrated by the flatworms, Platyhelminthes. This great phylum of worms includes the parasitic flukes and tapeworms, which are of great medical importance. My favorites, however, are the free-living turbellarian worms, of which there are more than 4,000 species: that's about as numerous as all the mammal species put together. They are common, both in water and on land, and presumably have been common for a very long time. You'd expect, therefore, to see a rich fossil history. Unfortunately, there is almost nothing. Apart from a handful of ambiguous trace fossils, not a single fossil flatworm has ever been found. The Platyhelminthes, to a worm, are "already in an advanced state of evolution, the very first time they appear. It is as though they were just planted there, without any evolutionary history." But in this case, "the very first time they appear" is not the Cambrian but today. Do you see what this means, or at least ought to mean for creationists? Creationists believe that flatworms were created in the same week as all other creatures. They have therefore had exactly the same time in which to fossilize as all other animals. During all the centuries when all those bony or shelly animals were depositing their fossils by the millions, the flatworms must have been living happily alongside them, but without leaving the slightest trace of their presence in the rocks. What, then, is so special about gaps in the record of those animals that do fossilize, given that the past history of the flatworms is one big gap: even though the flatworms, by the creationists' own account, have been living for the same length of time? If the gap before the Cambrian Explosion is used as evidence that most animals suddenly sprang into existence in the Cambrian, exactly the same "logic" should be used to prove that the flatworms sprang into existence yesterday. Yet this contradicts the creationist's belief that flatworms were created during the same creative week as everything else. You cannot have it both ways. This argument, at a stroke, completely and finally destroys the creationist case that the Precambrian gap in the fossil record can be taken as evidence against evolution.

Why, on the evolutionary view, are there so few fossils before the Cambrian era? Well, presumably, whatever factors applied to the flatworms throughout geological time to this day, those same factors applied to the rest of the animal kingdom before the Cambrian. Probably, most animals before the Cambrian were soft-bodied like modern flatworms, probably rather small like modern turbellarians—just not good fossil material. Then something happened half a billion years ago to allow animals to fossilize freely—the arising of hard, mineralized skeletons, for example.

An earlier name for "gap in the fossil record" was "missing link." The phrase enjoyed a vogue in late Victorian England, and on into the 20th century. Inspired by a misunderstanding of Darwin's theory, it was used as an insult, in roughly the same way as "Neanderthal" is colloquially (and unjustly) used today.

The original meaning, a confused one, implied that the Darwinian theory lacked a vital link between humans and other primates. History-deniers, to this day, are very fond of saying, in what they imagine is a taunting tone of voice: "But you still haven't found the missing link," and they often throw in a gibe about Piltdown man, for good measure. Nobody knows who perpetrated the Piltdown hoax, but he has a lot to answer for. The fact that one of the first candidates for a man-ape fossil to be discovered turned out to be a hoax provided an excuse for history-deniers to ignore the very numerous fossils that are not hoaxes; and they still haven't stopped crowing about it. If only they would look at the facts, they'd soon discover that we now have a rich supply of intermediate fossils linking modern humans to the common ancestor that we share with chimpanzees. On the human side of the divide, that is. Interestingly, there are as yet no fossils linking that ancestor (which was neither chimpanzee nor human) to modern chimpanzees. Perhaps this is because chimpanzees live in forests, which don't provide good fossilizing conditions. If anything, it is chimpanzees, not humans, who today have a right to complain of missing links!

Another meaning concerns the alleged paucity of so-called "transitional forms" between major groups like reptiles and birds, or fish and amphibians. "Produce your intermediates!" Evolutionists often respond to this challenge from history-deniers by throwing them the bones of Archaeopteryx, the famous "intermediate" between "reptiles" and birds. This is a mistake. Archaeopteryx is not the answer to a challenge, because there is no challenge worth answering. To put up a single famous fossil like Archaeopteryx panders to a fallacy. In fact, for a large number of fossils, a good case can be made that every one of them is an intermediate between something and something else.

The silliest of all these "missing link" challenges are the following two (or variants of them, of which there are many). First, "If people came from monkeys via frogs and fish, then why does the fossil record not contain a 'fronkey'?" And, second, "I'll believe in evolution when I see a monkey give birth to a human baby." This last one makes the same mistake as all the others, plus the additional one of thinking that major evolutionary change happens overnight.

Well, of course, monkeys are not descended from frogs. No sane evolu-tionist ever said they were, or that ducks are descended from crocodiles or vice versa. Monkeys and frogs share an ancestor, which certainly looked nothing like a frog and nothing like a monkey. Maybe it looked a bit like a salamander, and we do indeed have salamander-like fossils dating from the right time. But that is not the point. Every one of the millions of species of animals shares an ancestor with every other one. If your understanding of evolution is so warped that you think we should expect to see a fronkey and a crocoduck, you should also wax sarcastic about the absence of a doggypotamos and an elephanzee. Indeed, why limit yourself to mammals? Why not a kangaroach (intermediate between kangaroo and cockroach) or an octopard (intermediate between octopus and leopard)? There's an infinite number of animal names you can string together in that way. Of course hippopotamuses are not descended from dogs, or vice versa. Chimpanzees are not descended from elephants or vice versa, just as monkeys are not descended from frogs. No modern species is descended from any other modern species (if we leave out very recent splits). Just as you can find fossils that approximate to the common ancestor of a frog and a monkey, so you can find fossils that approximate to the common ancestor of elephants and chimpanzees.

As for the second challenge, once again, humans are not descended from monkeys. We share a common ancestor with monkeys. As it happens, the common ancestor would have looked a lot more like a monkey than a man, and we would indeed probably have called it a monkey if we had met it, some 25 million years ago. But even though humans evolved from an ancestor that we could sensibly call a monkey, no animal gives birth to an instant new species, or at least not one as different from itself as a man is from a monkey, or even from a chimpanzee. That isn't what evolution is about. Evolution not only is a gradual process as a matter of fact; it has to be gradual if it is to do any explanatory work. Huge leaps in a single generation—which is what a monkey giving birth to a human would be—are almost as unlikely as divine creation, and are ruled out for the same reason: too statistically improbable. It would be so nice if those who oppose evolution would take a tiny bit of trouble to learn the merest rudiments of what it is that they are opposing.

Excerpted from The Greatest Show on Earth: The Evidence for Evolution, by Richard Dawkins. © 2009 by Richard Dawkins. Reprinted by permission of Free Press, a division of Simon & Schuster, Inc.

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Fossils Shed New Light on Human Origins

By ROBERT LEE HOTZ

This image released by the journal Science shows the probable life appearance of Ardipithecus ramidus.


Researchers in the U.S. and Ethiopia on Thursday made public fossils from a 4.4-million-year-old human forebear they say reveals that the earliest human ancestors were more modern than scholars assumed and deepens the evolutionary gulf separating humankind from today's apes and chimpanzees.

The highlight of the extensive fossil trove is a female skeleton a million years older than the iconic bones of Lucy, the primitive female figure that has long symbolized humankind's beginnings.

An international research team led by paleoanthropologist Tim White at the University of California, Berkeley, unveiled remains from 36 males, females and young of an ancient prehuman species called Ardipithecus ramidus, unearthed in the Awash region of Ethiopia since 1994. The creatures take their scientific name from the word for root in the local Afar language. They are not the oldest known homind fossils but they comprise the most complete set discovered so far.

"It is not a chimp and it is not human," said Dr. White. "It gives us a new perspective on our origins. We opened a time capsule from a time and place that we knew nothing about."

Although the differences between humans, apes and chimps today are legion, all shared a common ancestor six million years or so ago. These fossils suggest that creature--still undiscovered--resembled a chimp much less than researchers have always believed.

In fact, so many traits in chimps and apes today are missing in these early hominids that researchers now question the notion that modern chimps and apes embody vestiges of humanity's primate past, retaining primitive traits once shared by human ancestors. "We all thought the ancestral animal would look more like a chimp," explained Yale University anthropologist Andrew Hill.

Instead, the new finds show that what seems most ancient about nonhuman primates today--such as canine fangs, long limbs with hooked fingers meant for swinging through trees and hands designed for knuckle-walking--may actually be the product of more recent development, the researchers said. In that sense, the human hand today actually may be the more primitive appendage, they said.

"It is the chimps and gorillas that have been evolving like crazy in terms of limbs and locomotion, not hominids," said Kent State University anthropologist Owen Lovejoy, a senior scientist on the research team. "We took a different tack. We went social."

Documented in 11 research papers to be published Friday in the journal Science, the fossils offer a detailed look at a species of sturdy, small-brained creatures that dwelled in an ancient African glade of hackberry, fig and palm trees, by a river that long ago turned to stone. Despite their antiquity, their bodies were already starting to presage humanity, the scientists said.

Indeed, unlike apes and chimps, they had supple wrists, strong thumbs, flexible fingers and power-grip palms shaped to grasp objects such as sticks and stones. They were primed for tool use, even though it would be another two million years or so before our ancestors began to fashion the first stone blades, choppers and axes.

There is no way to gauge these creatures' intelligence but they had brains barely bigger than the head of a golf club--much smaller than the more recent species, called Australopithecus afarensis, to which the Lucy skeleton belonged.

They were still evolving the ability to walk upright, with a big toe better suited for grasping branches than stepping smartly along, an analysis of their anatomy shows. They made their home in the woods, not on the open savannah grasslands long considered the main arena of human development. Yet their upright posture, distinctive pelvis and other toes suggest they walked easily enough. Most importantly, they showed no sign they walked on their knuckles, as contemporary chimps and apes do.

"They are not what one would have predicted," said anthropologist Bernard Wood at George Washington University.

Already, the discoveries have experts reworking the human pedigree. "They are extraordinary fossils," said anthropologist Alan Walker at Pennsylvania State University, who wasn't part of the project. They undoubtedly will shape debates about human origins for years to come, as scholars argue whether these creatures should be counted among our most ancient direct ancestors or cataloged as an intriguing dead-end.

"There are going to be generations of dissertations based on this," said Carol Ward, an independent expert on ancient anatomy at the University of Missouri, Columbia.

The project began simply with the discovery of a single tooth. But it soon grew into arguably the most comprehensive effort in the field of hominid studies, involving 47 scientists world-wide, as scores of unusually fragile and shattered specimens emerged from the rock. The skull, for example, was in so many pieces it had to be reconstructed digitally, requiring hundreds of CAT scans and 1,000 hours of computer processing. The pelvis alone took six years to reconstruct.

Moreover, the researchers also excavated and analyzed 150,000 other related fossils of animals and plants so that they could understand the conditions in which the creatures lived.

"We took enormous flak" for spending so much time analyzing the fossils, said Dr. Lovejoy. "We wanted to get it right and people had to wait until it was right.'

Write to Robert Lee Hotz at [e-mail]

[Elaine Friedland]

Those who view of the creation story literally, instead of as an allegory, have problems with understand the science of evolution. I think these two articles posted explain how the science of evolution views the development of human beings.

[Frank]

Eliane, I know noone who thinks that the Adam and Eve story is fact. However, I do not believ in the big bang or any of these other theroies that go around either. Lets look at Webster and see what it has to say about all this.
Creation; the act of creating, everything that has been created, the universe, something that has been created with imagination, bringing into being, the Creation of the world by God described in Genesis.

Evolution; a continuous change from a simple to a more complex form; the gradual developement e.g. of an idea, argument, plot, insitution or social group; the theroy that all living things have changed in responce to environmental conditions by natural selection of randomly occurring mutations, developing from the simplest forms to complex forms which are more prlific and stronger, due to their better adaptation to their environment.
If it is as you say everything came from one simple organisism why did it stop? If that theroy is true why are ther no more people evolving. A tadpole by end of sprin and well into summer become a grog. I would say that the tadpole had evoled.. But the fish when they break out of thier eggs sac in the spring they stay a fish, besdies the tadpole is there any living creature start life as one thing and then changes into something else? Now for the big question Elaine, lets say that all your therioes are true and they are proven to be so. Where did this first simple organisism come from? Was it created by what Einstein said a higher power, or did it evole from a what drop of water, grain of sand. Whne you come to the begining your theroy falls apart.

[Elaine Friedland]

Frank,

Those mutations which are beneficial will be passed on, while random mutation which aren't will cause the organism to fail to reproduce.

Contemporary Kabbalists, Jewish mystics, say that the big bang is similar to Kabbalist concepts If you are interested in explanation please read this http://www.myjewishlearning.com/practices/Ethics/Caring_For_Others/...

[Elaine Friedland]

Frank,

How do explain the fact that human beings have a vestige of a tail bone and the fact that human beings and chimps have common gene amounting about 98% of each genome? If we didn't share some many genes with chimps, science couldn't use chimps to test drugs.

There are still mutations occurring with human beings. I know of a group within Sierra Leone which are born with six fingers on each hand--the doctor cuts off the extra fingers at birth.

[Elaine Friedland]

Frank,

Here is more information on how recent research on DNA supports the theory of evolution
---------------

Samples of Genetic Evidence for Evolution: What Genes Can Tell us about Relationships & Evolution
Article by dgemmellaro (1,389 pts ) , published Aug 5, 2009

Read more: http://www.brighthub.com/science/genetics/articles/42290.aspx#ixzz0...

DNA Sequences

One of the most compelling pieces of genetic evidence for evolution is also one of the most basic. All living organisms use nucleic acids to encode genetic information; either DNA, or in the case of some viruses, RNA. The genetic code that specifies which DNA sequences translate into which amino acids is extremely similar in living things, with the only major differences being found in “simple” organisms like bacteria.

Many of the actual DNA sequences of complex genes are very similar among animals and the differences that do exist quite nicely reflect the degree of relatedness among species. For example, one gene that has been highly studied by scientists is the gene that makes the cytochrome c protein, which functions in the electron transport chain (the last stage of cellular respiration that takes place in mitochondria). The sequence of this gene in humans and chimps, our closest relatives, is virtually identical (with amino acid sequences being completely identical), while humans have varying degrees of differences in nucleotide sequences with other, less related organisms. The less related an organism is to humans, the more the nucleotide differences in the cytochrome gene. Scientists have found that there are:

* 13 nucleotide differences between humans and pigs
* 17 nucleotide differences between humans and ducks
* 20 nucleotide differences between humans and snakes
* 31 nucleotide differences between humans and tuna
* 36 nucleotide differences between humans and moths
* 66 nucleotide differences between humans and yeast
Genes and Relatedness

Though many genes are extremely similar and the degree of similarity also reflects the degree of relatedness among organisms, genes will often not be identical. This is to be expected given the idea that genetic mutations arise in DNA sequences, causing variation in a population (a basic tenet of modern evolutionary synthesis). Many scientists believe that there is a “basal” rate of mutation and the amount of variation within sequences can be used as a “molecular clock”; while this idea has some problems (rates of evolution can change depending on the gene being analyzed and the group being analyzed), the difference in the amount of mutation found when comparing species gives a good indication of when those species last shared a common ancestor.

The idea that gene sequences reflect relatedness is supported by such a large amount of evidence that it is even used in courts of law; this is the concept behind DNA profiling (like DNA fingerprinting) and paternity testing.

Evolutionary scientists can take the information observed in DNA sequences and construct what are called “phylogenetic trees”, which are essentially like family trees. By analyzing the differences and similarities in sequences among organisms, scientists can visually plot out the degree of relatedness among those species. These results are corroborated by other pieces of evidence as well, such as fossils and overall anatomical morphology.
Genes and Evolution

Moving on to a larger scale, we can look at the genes themselves and see that there are quite a number of genes that are shared by a wide variety of living things. These genes perform the same or similar functions in the genomes in which they are found, from the human genome to the fly genome. There would be no reason for organisms as different as humans and flies to have the same genes to perform similar functions, if not for the fact that they were descended from a common ancestor that possessed those genes. We’ve already looked at the cytochrome c gene; evolutionary scientists also invoke the opsin family of genes, which are used in light-sensing structures, more commonly known to us as “eyes”.

Perhaps the most famous of cases of stunning gene similarity among living things are the Hox genes. Essentially, Hox genes are genes responsible for laying down the basic body plan of an organism very early in its development; Hox genes, first found

n the fruit fly, establish what will be the front and back of an organism, and where structures such as limbs and eyes will develop; interestingly, the order of these genes on the chromosome perfectly correlates with the parts of the body that are influenced by particular genes. Not only are these genes found in virtually all organisms tested to date (including jellyfish), and not only are their sequences virtually identical in all organisms, but they are also found in the same order on the chromosomes of organisms studied. These genes are so identical that scientists have been able to take Hox genes from

one species and express them in another species; the genes function perfectly. For example, the gene governing limb development in chicks, called Sonic hedgehog, can be expressed in a shark and govern the perfect development of a shark fin.

One last piece of gene-scale evolution evidence can be found in what some scientists call vestigial genes. Just as vestigial structures are structures that at one time had a function for an organism but now essentially serve no purpose, vestigial genes are genes that were once expressed in an organism to make a protein product, but now are silent. Two classic examples are the gene responsible for Vitamin C synthesis (found but completely nonfunctional in the human genome and in higher primates) and odorant receptor genes, used in olfaction. The human genome contains around 100 odorant receptor genes, of which roughly 70% are completely nonfunctional; indeed, humans, and primates in general, are less dependent on their sense of smell than many other organisms. Dolphins contain numerous odorant receptor genes, with not even one being functional; dolphins, in other words, have given up their sense of smell. Again, there would be no reason to have genes without any function whatsoever unless they were passed along through common descent.
References

The Shape of Life: Genes, Development, and the Evolution of Animal Form (Raff, 1996)

Evolution (Mark Ridley, Ed., 1997)

From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design (Carroll et al., 2001)

Asking About Life (Tobin and Dushek, 2005)

Biology: A Guide to the Natural World (Krogh, 2005)

The Chimpanzee Sequencing and Analysis Consortium. "Initial sequence of the chimpanzee genome and comparison with the human genome." Nature, 2005.

Your Inner Fish (Shubin, 2009)

http://www.talkorigins.org/faqs/comdesc/section1.html


http://www.brighthub.com/science/genetics/articles/42290.aspx

--------

DNA Evidence for Evolution: Chromosomes, the Fossil Record & Practical Applications of the Theory of Evolution

Read more: http://www.brighthub.com/science/genetics/articles/42293.aspx#ixzz0...

Chromosomes and Evolution Evidence

Chromosomes, or the higher order structures that contain genes, are also analyzed to support the theory of evolution. Scientists compare chromosomes among species or other large groups of living organisms and “tally up” the differences. The result is that groups that are less related will have a greater number of structural differences, or rearrangements, in their chromosomes. An extremely important piece of chromosomal evidence for evolution was discovered in 2005. It was observed that our closest relatives, chimpanzees, gorillas and orangutans, possess 48 chromosomes, or 24 pairs (one pair coming from mom and one coming from dad), while humans possess 46 chromosomes, or 23 pairs.

According to the theory of evolution, because we are so closely related to these apes in genetic terms, the difference in our chromosome numbers must have one of two explanations. Either the human lineage lost a chromosome or there was a fusion between two chromosomes. Losing a chromosome would be out of the question biologically, given the fact that such a huge loss of genetic material would certainly be fatal for an organism. Once scientists started looking for evidence of chromosome fusion, however, they were surprised at how easy it was to find. Indeed, human chromosome 2 is now accepted by scientists as having resulted from the fusion of two ancestral chromosomes, still found in apes; in apes, the original chromosomes are now called 2A and 2B.

Populations

The last level to examine for genetic evidence of evolution is the population level. The modern evolutionary synthesis postulates that there is genetic variation in populations of living organisms and over time, some alleles (or alternative versions of genes) will become more or less prevalent in a population, depending on circumstances. This concept is no more obvious than in the case of antibiotic and pesticide resistance in bacteria and insects. Some bacteria, even before the advent of mass-produced antibiotics, possessed the occasional antibiotic resistance gene. When humans introduced antibiotics on such a massive scale, we “favored” those bacteria which possessed resistance, thereby changing the genetic composition of the bacterial population.

This has also been observed in the laboratory. Dr. Richard Lenski, at Michigan State University, observed that cloned (genetically identical) E. coli actually displayed genetic diversity after 40,000 generations. Furthermore, he placed these bacteria in test tubes full of citrate, which E. coli cannot normally metabolize; after around 30,000 generations, a mutation arose that allowed the bacteria to utilize the citrate as a food source.
Practical Applications of the Theory of Evolution

Not only are these genetic similarities useful for humans in order to support evolution, but they also have a much more practical application for us. Indeed, they are the basis for the use of “model” organisms. Because of the ethics involved in doing experimentation on humans, many other organisms are used to understand basic physiological and disease processes in humans. These model organisms can be successfully used because of the similarities in the gene structure and biochemical processes among living things. Many organisms can also provide insight into how to treat medical illnesses; it is thanks to the ideas of evolutionary theory, for example, that mice have provided so much insight into the study of cancer.


More than Just the Genes

Even though there is a an enormous body of genetic evidence that supports evolution, this evidence is given even more weight because of the corroboration of its conclusions from other scientific disciplines. The fossil record, for example, reflects what the genes tell us. In very broad terms, when comparing DNA sequences, scientists find that humans have more in common with mice than with frogs. The fossil record says that amphibians appeared on Earth way before mammals did, so humans and mice share a more recent common ancestor than do humans and frogs, which explains why they are more genetically similar. All other observations point to the same conclusions.


References

The Shape of Life: Genes, Development, and the Evolution of Animal Form (Raff, 1996)

Evolution (Mark Ridley, Ed., 1997)

From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design (Carroll et al., 2001)

Asking About Life (Tobin and Dushek, 2005)

Biology: A Guide to the Natural World (Krogh, 2005)

The Chimpanzee Sequencing and Analysis Consortium. "Initial sequence of the chimpanzee genome and comparison with the human genome." Nature, 2005.

Your Inner Fish (Shubin, 2009)

http://www.talkorigins.org/faqs/comdesc/section1.html



Read more: http://www.brighthub.com/science/genetics/articles/42293.aspx#ixzz0...

http://www.brighthub.com/science/genetics/articles/42293.aspx

[Elaine Friedland]

The Genetic Evidence for Human Evolution
From: The Natural History Museum | By: Chris Stringer


it has been discovered that we share a huge amount of DNA with our closest primate relatives. It has been calculated that we share 98 to 99 percent of our DNA with chimpanzees. The differences between humans and chimps may seem profound, but when you look at the genetic codes they are overwhelmingly similar. There are in fact two species of chimpanzees, common chimpanzees and bonobos, and we are equally related to both. DNA studies have shown that of the apes, chimpanzees are our closest relatives, followed by gorillas, the other African great ape, followed by orang utans, the Asian great ape, followed by gibbons, which are smaller apes. This reflects the order of divergence. We think that humans shared a common ancestor with the apes and that the different species split off from there; first the gibbons split off, then the orang utans, then the gorillas, then the chimpanzees, leaving humans with their own line of evolution. Researchers have analysed the amount of difference between human and chimpanzee DNA and estimated that in order to accumulate those differences, the two species would have split between 5 and 7 million years ago.

Despite all the different shapes and sizes and colours of humanity, the evidence from mitochondrial DNA tells us that we are actually very, very similar. Comparing the differences between human mitochondrial DNA around the world with the differences found within just one small troop of chimpanzees or gorillas in central Africa shows that a single ape troop contains greater diversity than all of humanity! In fact relative to many other species, we're almost clones of each other. This is consistent with a recent origin for our species and also with the view, held by some scientists, that there was a bottleneck some time in our recent evolutionary past. It seems likely that within the last 200,000 years, the human population went down to a very small number, to maybe only 10,000 or 20,000 people, reducing the genetic diversity that gave rise to today's population. This may well be why humans today show a relatively low diversity compared with many other species. Chimpanzees, in comparison, have had a long and quite complex evolutionary history; their diversity may have been developing for over 1 million years.

Genetic studies for modern human origins I think it really took off in 1987 when seminal work on mitochondrial DNA was published in the journal Nature. The three authors of that paper caused quite a sensation because, for the first time, they had looked at the mitochondrial DNA types of about 150 people from all over the world, from Africa, Europe, New Guinea, etc.--members of the different so-called races. They used a computer to build up a tree of the relationships of all those different types. The tree assumed the minimum number of mutations needed to account for all the difference found among the samples and charted common ancestors going further and further back in time until it eventually arrived at a single hypothetical ancestor for all the people living today. Since this is mitochondrial DNA, that ancestor is female, so she was termed 'Mitochondrial Eve'. By making calculations based on the number of mutations, the authors were able to pinpoint that Eve lived approximately 200,000 years ago--relatively recently. And that wasn't all. From the structure of the tree that the computer constructed, they deduced two fundamental branches. One branch was African and was found only in Africa, the other included both Africans and non-Africans.


The authors thus concluded that Mitochondrial Eve lived in Africa and that some of her descendants stayed behind in Africa whilst others went out and founded the populations in the rest of the world. This was revolutionary because it indicated that the ancestral stock lived in Africa quite recently and gave rise to all the variation we find today in really quite a short period of time. It also concurred with the 'Out of Africa' theory which had suggested just this pattern of events, based on the fossil evidence.
http://www.fathom.com/feature/190159/
So the Genesis' allegory is teaching us the same as science: we all have a common origin no matter how we look., no matter our skin color, eye color, hair type/color. facial features etc.

By the way, the research on Mitochondrial DNA and Y chromosome DNA enables geneticists able to trace human migration.

[John Fisher]

But even still Mitochondrial DNA has been unable to link Homo Sapiens to Homo Habillis, nor has it linked Homo Habillis to Australopithecus Africanus and they have been unable to show that these inter-species were able to mate and provide offspring. Until they do Evolution requires faith. Much like creation does. So it becomes a matter of who do you believe more. Moses or Charles Darwin?

My objection to the school of evolution is that it requires blind faith and the rejection of creationism. Creationism does not reject evolution. What it says is that G-d created man both male and female. It says that man was created from the dust of the earth. It says he did this in one day. What is a day to G-d? It could have been millions of years I do not know I will ask Him next time I see Him. Evolution says that man came from mud. What is mud, but wet dust. Can Evolution fit within the creation story? Yes it can. But my problem is that evolution requires me to call Moses a liar.

[Elaine Friedland]

Who's Who in Human Evolution

Despite a fragmentary fossil record augmented by rare, sometimes surprising new finds like Homo floresiensis, paleoanthropologists have assembled a very solid general picture of human evolution. In this clickable illustration, follow the trajectory of hominin development as it is currently known. As the illustration makes clear, scientists have traced hominins—that is, species more closely related to humans than to other apes—all the way back through the australopithecines, like the three million-year-old Lucy, to Sahelanthropus tchadensis, who lived over six million years ago. The key feature that all these hominins share is bipedalism, which separates hominins from the primate line that eventually produced today's chimpanzees and other great apes.—Peter Tyson
http://www.pbs.org/wgbh/nova/beta/evolution/whos-who-human-evolutio...
The Adaptable Human

* Posted 10.26.09
* NOVA

The human family tree is full of dead branches, cousins to us modern humans that went nowhere. What enabled our kind, Homo sapiens, to arise and persist? Rick Potts, a paleoanthropologist at the Smithsonian Institution, sees evidence that early humans were adapted to change itself, specifically the frequent and severe environmental changes that occurred in Africa and elsewhere beginning around 800,000 years ago. In this interview with anthropologist Graham Townsley conducted at Potts's research site at Olorgesailie in Kenya, Potts talks about how he came to this way of thinking, what pigments found at the site say about our evolution, and why the jury is still out on how successful Homo sapiens really is.

Editor's note: Olorgesailie is an early human site in southern Kenya first discovered by Louis and Mary Leakey in the 1940s. Since the early 1980s, Potts, Director of the Human Origins Program at the National Museum of Natural History, has been excavating the site, which is noted for its large number of handaxes made by Homo erectus between 600,000 and one million years ago.

BIRTH OF AN IDEA
What was it that originally led you to formulate the climate variability hypothesis?

Climate change had always been on people's minds when it came to human evolution. The idea that was around for a long time is that the establishment of a savanna environment, the grassy environment with a few trees, was critical to human evolution early on, and that and the Ice Age later on presented the challenging environment in which humans evolved.

But when I began the work here at Olorgesailie, we kept seeing layer after layer of environmental change, from soils to volcanic ashes to a lake to a drought when the lake completely evaporated. We saw this through 700,000 years, and I began to think, well, maybe it's not the particular environment of a savanna that was important, but the tendency of the environment to change, to vary in very dramatic ways. And we saw that the large grazing animals of the savanna—elephants, baboons, pigs, zebras, all of whom ate grass—disappeared in the time period when worldwide climate began to vary the most.

So it dawned on me: Rick, you're an anthropologist. Maybe this has something to do with human evolution, and it's not the survival of the fittest in any one environment but the survival of the more versatile, the more general and flexible creatures that would really persist over time. This gave me a new insight into human evolution. The origin of stone tools, the expansion of the brain, and the complexity of social life that we see with the emergence of our own species may actually be a response not to just the dry savanna or the cold Ice Age but to the wide and dramatic variability of climate over time.

We have not yet proven whether we can be as successful even as Homo erectus.

How condensed could these periods of climate variability be?

In some cases the landscape change occurred within a few thousand years. But this is all within a larger cycle of changing—Earth's orbit around the sun, and changes from wet to dry in tropical Africa, and, later in time, changes that were on [a scale of] 100,000 years between ice ages and interglacial warmth.
So you were able to correlate these periods of intense climate variability with the important steps in human evolution?

Olorgesailie inspired our idea that climate variability was an important driving force in human evolution. But we had to look outside of Olorgesailie to many other early human sites to really test the idea. What we have found is that the most prolonged periods of climate variability early on corresponded with the origin of stone tools and of eating meat, and the origin of our own genus, Homo. Then, later on, another prolonged period of climate variability, very dramatic, corresponded with the origin of modern human behavior and our own species.

So it really does look, on the grand scale, as if these pulses of climate variability were the engine that was powering human evolution?

When you think about it, we started out as a tropical African ape-like population and species, and after a period of diversification of our family tree—and extinction, real survival challenges—we now end up with one species, our own, spread all over the world. That's a story of adaptability. And so the question that we've posed is, How does adaptability evolve? It seems like it would evolve in relation to vast and dramatic climate changes.
NATURAL SELECTION AT WORK
But survival works on the basis of the individual. How could a quality like adaptability, which would only become evident over hundreds or thousands of years and many generations, be selected for?

Generally, the idea of natural selection involves the reproductive success and survival of individuals. But when we're looking at evolution by natural selection, you have to take into account the success of individuals not only living at the same time in one generation but over many generations. And what the environmental sciences have contributed is [the notion] that the environment changes. The rules of the survival game are upturned every once in a while, and the descendants of a single lineage will experience many different environments over time. So the idea of variability driving evolution is the idea that adaptability will evolve in relation to vast periods of environmental change over time.
But despite its success as a species, Homo erectus ultimately couldn't adapt.

Right. What we see in this record of vast environmental change here is that Homo erectus and the handaxe makers had a very enduring and adaptable way of life, but ultimately they became extinct. And it brings up the question: Why did their way of life dissolve? Well, we have our own species now, highly adaptable, spread all over the world. It seems like we might persist forever. But evolution brings up this point of: What tips the balance between persistence, adaptability, and success, as in Homo erectus and our own species, but then extinction?

I like to think of them as the lawnmowers of the Pleistocene.

And Homo erectus was around an awful lot longer than we've been. People think that we, Homo sapiens, are this great thing.

Yes. The handaxe makers here at Olorgesailie and at other sites in East Africa, and the species Homo erectus, were around for about 1.5 million years—a vast period of time. Our own species has only been around for about 200,000 years, as far as we know—just a blip of evolutionary time. So, yes, we see ourselves as successful, spread all around the world, and sort of at the top of the heap. But we have not yet proven whether we can be as successful even as Homo erectus.
So the jury is still out on sapiens.

That's right. The jury is still out on sapiens.

SITE OF CHANGE
You know this landscape here so well. If we could see a million years of history of Olorgesailie speeded up and watch it in five minutes, what are some of the changes we would see in this environment?

The starting point of the environmental history of this region was a volcanic plain. It was probably a very forbidding place, but as the volcanic landscape cooled, there were earthquakes and then sort of pockets in which rainwater could accumulate, and that was the beginning of the lake. And the lake spread over time. We see the glaring white sediments of the lake expanding and then contracting. There were periods of drought. This was interrupted by periods of volcanic eruption, times when pumice and ash would rain down on the landscape, sometimes killing off all the grass. The animals would need to move away. The handaxe makers kept coming back, though, through all these different layers.

Sometimes stream channels and rivers would come through the area, and the lake would come back again. Over and over again these enormous changes [occurred] in the water resources and the food that early humans and other animals needed to survive. We then see about 500,000 years ago that earthquakes lifted up this entire region, and the lake completely drained away. That led to a landscape that was cut into vast valleys and then filled up again with sediment, depending upon whether it was dry or wet.

The last event we see here recorded in the sediments was about 60,000 years ago, when it was a probably very wet time. Due to earthquake activity maybe 100 miles to the north, an enormous amount of water rushed through and boulders were driven into this area. An awful time to live here. Then, as you can see, the valley was cut again, and it's an incredibly dry place today. So, despite these dry, dusty sediments that we dig, this was once a well-watered place, but a place of immense environmental change.
Lots of other animals survived these changes along with our human ancestors. What distinguishes those species that survived from those that didn't?

Well, it's interesting that as we have excavated through these different layers, we have found evidence of large elephants and enormous pigs, and baboons and zebra and hippopotamuses, all of which were specialized in their chewing apparatus—their teeth and the muscles that move their jaws—toward eating grass. I like to think of them as the lawnmowers of the Pleistocene. They ate grass, and they ate it in abundance. But as we see evidence of an increase in environmental variability through time, we see, as I mentioned, that those animals go extinct. The savanna animals were not the ones that survived.

Rather it's their cousins, such as the baboons today that can eat tree leaves as well as grass and dig for underground resources with their hands, or elephants who can live anywhere from deserts to forested environments, who are the real survivors in Africa today. And we're part of the picture, too. The handaxe makers may have been part of the fauna that was adapted to environmental changes, but mainly in open kinds of habitats. But when environmental variability increased even more, their way of life went away, and a more adaptable, more flexible way of life, represented ultimately by our own species, evolved.

Does evolution always favor generalists?

Evolution favors both generalists and those species well adapted to specific habitats—as long as those species can move. When we see these environmental changes, wet and dry, we see that the favored ranges, the favored habitats of particular animals, sometimes become smaller, or they expand, or they move to the south or north. It's critical for animals that are adapted to specific environments to be able to track those habitats. In some ways, they can stabilize the conditions of natural selection. Without the ability to move, as when there are fences or highways or cities, they're in a lot of trouble in the long-term.
ROOTS OF SYMBOLISM
You've found pigments at this site. Is it true that these are the very first pigments ever found?

Yeah, these are the earliest known pigments, at least in an archeological setting that is well dated. We have a volcanic ash that is represented in the pile of sediments here dated to 340,000 years ago, and this is below that, so it's older in age.
What might the early humans here have used these pigments for? What did they signify?

We don't know exactly what these pigments would have been used for. But they could represent the first really clear symbolic objects, in terms of people marking objects, marking themselves, creating a sense of group identity. What symbolism means is that you have the ability to recall the past in a better way, to plan for the unexpected, and also to imagine the future.

There were tremendous survival advantages in being able to create a symbolic world that people in another place could understand. You could begin to have shared beliefs, shared values. And even something as simple as the exchange of valued raw material that could be made into sharp hunting objects over tens or hundreds of miles meant that these people had a unity, a group unity, which really is the beginning of a modern human way of life. We all create for ourselves a symbolic universe. We live in a symbolic world, and these could be the rudiments of just that world.

Our own species has evolved an ability to diversify our options.

Do you think the innovation of symbolism gave our ancestors an adapted survival advantage in times of environmental change?

During times of climate instability, such as the time when we see these innovations, just think of what would happen if the food in your environment or the water dried up. You couldn't find food, you couldn't find water. Well, having a symbolic connection with people a hundred miles away, having an exchange network with that group so far away, meant that you could have, in a sense, an insurance policy against the survival challenges in your own place. You could rely upon sharing the survival resources available in another place.

When we think about our own lives and the ways in which we depend upon people, whether it's global aid to help people in times of catastrophe or even our own insurance policies, we're really seeing the beginning of that way of thinking right in these little objects 350,000 years ago.


EXTINCTION AMONG OUR KIND
When you look back to these periods of high variability, do you envisage large die-offs among hominid species? Does evolution happen faster when populations are reduced to tiny pockets?

The human family tree is full of experiments in being human—twigs and branches on the tree. It's as full as the evolutionary histories of other organisms, but there's only one surviving human now, and that's us. Our family tree is full of dead branches.

And what we see in the lives of the earlier humans is that they lived in small populations, sometimes isolated from one another. In some ways, even on vast continents like Africa, they may have lived on what would have been almost little continental islands, habitats that they favored in particular. But that's a situation where in the long-term there's going to be a lot of origination of species and extinction. That seems to characterize our own family tree.

So when you look at human evolution in the context of the dramatic environmental changes on Earth, and even in particular regions like East Africa, you can see the reasons why there would be a number of experiments in being human—Homo erectus, Homo heidelbergensis, Neanderthals, and so on. And you can see also why they persisted for a long period of time and then became extinct.
In that respect, there's nothing special about humans. That's true of any animal species.

Well, one thing that's part of the adaptability our own species has evolved is an ability to diversify our options. We have different cultures. We're characterized by cultural diversity in a way that no previous early human had been. One wonders whether this may be our ultimate card to success, as long as we can keep those options open. Neanderthals were the Ice Age specialists. Homo erectus, while spread over a wide area, had essentially one way of life, and ultimately their way of life became extinct. Human beings today are all over the place in terms of the many diverse ways we live, and so perhaps that will be the most important thing with regard to the success of the only remaining human species today.

Interview conducted August 9–11, 2008 by Graham Townsley, producer of "Becoming Human," and edited by Peter Tyson, editor in chief of NOVA Online
http://www.pbs.org/wgbh/nova/beta/evolution/adaptable-human.html

[John Fisher]

In your chart it shows an "inferred" relationship between Homo species and the others. It has yet to be proven. Thus it is nothing more that an Idea and not fact and far from scientific fact. It is a hypothesis nothing more. Until the link can be proven and the species are shown to be able to create offspring it has less standing than Moses. I do not know many Jews that would come out and call Moses a liar.

[Elaine Friedland]

How do you explain the fact that our species--homo sapiens--shares DNA with our species?

The overwhelming majority of the Jewish community accepts evolution as a scientific theory and only the Ultraorthodox Hareidi. would reject this viewpoint. When I was a child attending Shabbat services our Rabbi would take the children into his study for a discussion of the Torah portion during the Torah reading. In terms of the parashat Bereishit, our Rabbi emphasized that it is to be considered as allegory, not something literal.

I am currently listening to online lessons (from Mechon Hadar http://www.mechonhadar.org/) on the midrash (Bereishit Rabbah) concerning Bereishit. Jewish theology in terms of Bereishit is not all like what you were taught as a child when you attend the Sunday School in the church favored by your family.

[Elaine Friedland]

To add, I have already mentioned to you Rambam, one of the greatest Jewish philosophers, who lived in Egypt, during 12th century. He states that the Torah operates on many levels. The simplest level is the literal, which is for the person of the least intellectual ability. However, that should not deter anyone from delving deeper into the hidden meanings and symbolism of the Hebrew words. Science and Torah do not contradict, but only merely appears to when one stops ones analysis at the literal meaning. In Jewish tradition, when Moses received the Written Torah, he also received the Oral Torah (Torah Shel b'Peh) This Oral Torah became the basis for Talmud and Midrashim. Hence if Rambam were alive today, he would have no problem with science of evolution.

What could the connection Hebrew word for human Adam (human beings are bnai adam, children of adam) and the Hebrew word for earth adamah symbolize? (By the way, the Hebrew word for man is ish.)