WinAce

Evidence that apes and humans share a common ancestor comes from many fields. Below will be only a partial list, to give you an idea of just how overwhelming it is.

(1) Fossil intermediates morphologically intermediate between modern apes and modern humans.

Exhibit A, below, taken from the TalkOrigins 29 'Evidences' for Evolution FAQ:



Fossil hominid skulls. The first, A, is a modern chimpanzee. The last, N, is a modern human. Those in-between are some of the more important fossils we've found, arranged in linear order. Notice how the earliest fossils are more and more ape-like, whereas the later ones are more and more human-like. The ones in-between more or less completely blur the line between human and ape, possessing excellent combinations of primitive and derived traits. Especially note the less elongated jawline and increasing brain size from earliest to latest skulls.

The theory of common ancestry imposes very stringent restrictions on what we should find and (and not find!) in the fossil record. Since we see a linear change from less human to more human, the theory is spectacularly corroborated. Since we don't ever see any fossils that are totally prohibited by evolution, such as apes with eagle eyes or other mix-and-match uses of the best designs available, evolution is doubly corroborated.

Both tests (as well as others) are an empirical experiment that tests evolution's validity. It passes with flying colors.

(2) Identical pseudogenes in apes and humans that corroborate the powerful fossil evidence.

Taken from the TalkOrigins Plagiarized Errors and Molecular Genetics FAQ:

Pseudogenes are formerly active genes that have been been the victims of crippling mutations and no longer express protein. Our genomes are littered with them, from the GLO pseudogene that produces vitamin C to dozens that control the olfactory systems in other mammals.

Normally, genes are preserved quite well by natural selection, and individuals with crippled genes are filtered out of the population. Occasionally, however, a gene with no mission-critical function will get deactivated and the organism can get along equally well without it. For example, a gene coding for the production of a protein that's abundant in the animal's diet anyway is irrelevant to its reproductive fitness.

Crippling mutations come in literally dozens of varieties: parts of the gene may become overwritten with another; parts of the gene may be cut out; random detritus can be spliced in, breaking its function; two genes can be merged together; parts of the gene can be shuffled with other parts; etc. We know they occur because we observe them in the lab and can even artificially induce them.

The causes of mutations range from errant cosmic rays to toxins in the environment. The common adage of "no two snowflakes are alike" applies even more here, as the odds of getting the same crippling mutation twice are somewhere in the astronomical range.

This leads us back to the newly formed pseudogene. As long as it bears no selection disadvantage, random genetic drift can establish the damaged gene in a small population. Should that population be successful and displace the others, the gene will be established in the entire species as a molecular vestige.

Any two offshoot species will hence be identifiable as related if they share the same crippled mutations in damaged genes. Does this apply to humans and apes?

The answer is a resounding "Yes!". Examples are listed below.

Primates, unlike all other mammals (with the exception of guinea pigs), cannot synthesize Vitamin C. In days long past, this led to tragic outbreaks of scurvy on seafaring voyages. Using the predictions of evolution, scientists hypothesized that the gene for vitamin C production would be found in humans as well, despite our not being able to produce it.

Lo and behold, a GLO (ascorbic acid pseudogene) was identified in humans at exactly the same spots other mammals have functional vitamin C genes. What's more, the other great apes (chimps, gorillas and orangutans) had an identical broken pseudogene!

The common ancestor of apes and humans lived in a fruit-rich environment and had no need to synthesize their own vitamin C, making the loss of that gene entirely neutral. Guinea pigs also have a damaged GLO pseudogene, but the mutation that crippled it is different, as expected if it was an independent occurence.

Other occurences of shared pseudogenes include the one coding for Urate Oxydase, which make our species vulnerable to gout, and dozens of them that code for powerful smell in other animals but are crippled in humans, but one should suffice for now.

Observations in the area of pseudogenes that would falsify evolution include finding the same pseudogene in humans and dogs but not apes; since apes and humans share a closer ancestry than dogs and humans, any pseudogenes found in dogs and humans MUST be found in humans and apes because they belonged to the common ancestor of the latter. Hence, the theory of evolution passes this series of empirical experiments as well.

(3) Atavisms. Lost traits indicative of our species' history that occasionally resurface in modern individuals and again corroborate hypothesized evolutionary relationships.

Taken from here:



Exhibit B, X-ray image of an atavistic human tail. The subject is a 6-year old girl.

Note: pseudotails are an entirely different phenomenon and unrelated to real human tails. Pseudotails are merely abnormal protrusions of skin and muscle in the sacral region, whereas some real human tails have nerve ganglia, cartilage, additional vertebrae, and can be consciously moved and contracted. In addition, cases have been reported where they've been inherited in families.

Human fetuses are frequently covered in a minute fur (called lanugo) that becomes reabsorbed shortly before birth. Rarely, this feature is retained, resulting in what is known as Werewolf Syndrome by the press - a human covered in thick, animal-like fur.

This evidence more or less speaks for itself, but I'll offer a few additional comments. Atavisms are another empirical test for evolution's validity. The theory predicts only those atavisms that reflect traits in ancestral species will be found. This, for example, means that finding wing atavisms on a human, gills on a whale, fur on a fish, or some such, immediately and uncontrovertably falsifies evolution.

On the other hand, finding excessive fur on a human, developed hind legs in whales or snakes, or other atavisms totally consistent with their hypothesized evolutionary history is a strong confirmation.

(4) Human chromosome 2 is an exact duplicate of two ape chromosomes, but they're fused together. Humans also have 1 less chromosome than apes. Coincidence?

From here:

A rare mutation exists that can fuse two chromosomes into one. It's been observed in the lab and accounts for several cases of chromosome number discrepancy between domestic horses and wild ones, species of mice, and others. While it normally results in infertility and death, occasionally no important DNA is affected by the chromosome fusion and it can be passed on to descendants.

It's long been known that humans and apes have a different number of chromosomes; some have argued this is evidence they are not related, in fact. But biologists hypothesized that the discrepancy was accounted for by a chromosome fusion and made several tantalizing and very unlikely successful predictions as to how our genome should look.



Exhibit C; human, chimp, gorilla and orangutan chromosomes lined up. Notice the banding patterns on human chromosome 2 and how they look identical to 2 different ape chromosomes. Both arrangements work equally well, as location on chromosomes does not affect activity of genes; nevertheless, instead of two different chromosomes or one large one, ours is fused as a perfect evolutionary vestige.

But do mere looks tell us that indeed, this is a genuine fused chromosome from our ape-like ancestor? The conclusion would already be reasonable given the evidence, but the theory of common ancestry predicts yet more observations.

Chromosomes end in what are known as "telomeres" that are identifiable repeats of the same DNA bases. Conversely, they also contain characteristic "centromeres" near the middle. If our chromosome 2 was fused from two ape-like chromosomes, we would expect to find the inverse; telomeres in the middle, where the two old ones met, and centromeres halfway toward each end from the middle, as opposed to the middle itself.

Both predictions are true. Centromeres and telomeres have been identified in human chromosome 2 exactly as evolution told us they would.

This was another experiment to demonstrate the truth of evolution: had humans had no traces of the fusion, we would be hard-pressed to account for the discrepancy without seeing any remnant of the missing one. Not only would hundreds of genes on the chromosome be deleted in the process, almost assuredly rendering the mutant infertile or worse, but mutations that delete entire genes or chromosomes without leaving a trace are spectacularly rare.

Had this been due to deliberate design, we would likely see two different fused human chromosomes. Or one large one, but without the bizarre misplaced centromeres and telomeres that only lead to the conclusion of common ancestry. Both would be falsifications of evolution.

(5) Endogenous retroviral infections from the ancient past and their role in confirming what is already painfully obvious.

Taken from here:

Retroviral infections can occasionally infect a germ line cell. The resulting offspring will have bits and pieces of the virus stuck in every cell in its body. We've observed this very rare process in the lab, and the odds of getting two independent infections to leave the same bit of viral DNA at the same exact locus are astronomically unlikely.

Like pseudogenes, the viral fragments can piggyback on the success of an individual and become established in the species. The chances of any particular viral fragment, even if inserted identically in two seperate cases, becoming established in two seperate populations (a rare event in and of itself) makes this not just improbable, but more or less impossible without divine intervention

Any offshoot species will have the same unlikely and easily identifiable ERV, enabling us to construct accurate phylogenies from an independent line of evidence.



Exhibit D; human endogenous retrovirii insertions in identical chromosomal locations in various primates. Notice just how well the standard evolutionary phylogeny (humans and chimps closest, then orangutans and gorillas, then gibbons, then old world monkeys, then new world monkeys) is represented by this line of evidence.

ERVs have also been used to reconstruct the relationships between dogs, jackals, wolves and foxes; various breeds of domestic cat and wild cat; and even to establish the shared ancestry of cows and whales. (In the last case, two independent viral infections accounting for the evidence is impossible - whales and cows do not even share the same environment, much less are exposed to the same diseases!)

Needless to say, this offers numerous falsification avenues for evolution. Any ERV shared between organisms farther on the phylogenetic relationship than humans and apes must *also* be found in both. For example, ERVs found in New World Monkeys and chimps MUST be present in humans (aside from a few very rare cases where they've been deleted, but we can tell when a deletion has occured) or evolution is falsified.

An ERV in dogs and humans but not chimps would put the theory on its deathbed; so would a phylogeny reconstructed from these viral fragments if it differed significantly from the accepted phylogeny based on morphological, fossil, pseudogene, anatomical, and other evidence. This is the strongest evidence for evolution I've ever come across; a truly powerful and damning smoking gun.

Hypotheses proposed by creationists to account for this are inadequate: one entails independent insertion by the same virus affecting different species.

The fact that ERVs, when analyzed, yield evolutionary phylogenies consistent with the ones based on morphological, fossil and other evidence (as opposed to, say, viral infection patterns instead) rules out the independent insertion hypothesis as unlikely. The fact that species that don't even share the same environment, much less diseases (like cows and whales) share unique ERVs falsifies it completely.

Conclusion

These 5 lines of evidence (and there are many more) are all not just explained by evolution, but predicted by it. Each one could mean falsification and relegation to the scientific dust bin of history, along with phlogiston and a geocentric earth, or repeated vindication to the point where "nothing in biology makes sense except in light of evolution", as stated by Theodore Dobzhansky.

Each is an empirical experiment that most certainly establishes that common descent is not only science, but one of the most well-supported theories in all of science.

Whether one believes in god(s) or not, the evidence is clear - apes and humans share a common ancestor. The origin of that evolutionary process is a seperate question entirely and the scientific facts cannot (as of yet) clue us in on whether deity(ies) were involved, so evolution is not a threat to religious beliefs.

RufusAtticus

I see your one chromomsome, and I raise you an entire karyotype.

caravelair

very interesting! thanks.

Wounded King

The poor modern chimp, he looks 2.6 million years old if hes a day. It must be an easy life in them rainforests if the chimp hasn't diverge significantly morphologically from the common ancestor of chimps and man.

Doubting Didymus

Excellent excellent EXCELLENT.

Exceptional! Someone keep a copy!

Actually, I'd like to see this published in the agora. Is that possible?

SanDiegoAtheist

Well, we're the ones who had to muck about with our environmental fitness by leaving the trees and deciding the savannahs looked like a better idea

Cheers,

The San Diego Atheist

WinAce

Thanks for the compliments, but I don't think my post is polished enough for publishing (yet). I hope to eventually make a very short yet powerful essay on this subject, but that'll require tracking down all sorts of obscure references and addressing the flaws in proposed creationist explanations for this data.

Celsus

If you are interested in publishing for the Agora, remember to get permission to use those diagrams/pictures. With that out of the way, go here and follow the instructions.

Joel Ng

WinAce

Hmm, no creationist replied yet? How ... unusual.

Albert Cipriani

Dear WinAce,
You wrote: Likewise, the evidence is clear -- humans and amoeba share a common supernova ancestor.

Likewise, if life is seen as I see it, as a spark that cannot be quenched, then the evidence is clear that humans and amoeba share the same spark of life in that neither of us have died. The life we presently have and may pass on before we lose it is immortal.

Ergo, my point is, what's your point? That humans are genetically similar to apes indicates what? You call it common ancestry. I call it common-law lives.

That which is alive today has always been alive. All living things derived from every other living thing. This seems to me to be a truism, a matter of fact, not something that means anything. Do you mean something? -- Sincerely, Albert the Traditional Catholic