Evolution study tightens human-chimp connection

EurekAlert (AAAS) ^ | 23 January 2006 | Staff

[PatrickHenry]

Scientists at the Georgia Institute of Technology have found genetic evidence that seems to support a controversial hypothesis that humans and chimpanzees may be more closely related to each other than chimps are to the other two species of great apes – gorillas and orangutans. They also found that humans evolved at a slower rate than apes.

Appearing in the January 23, 2006 issue of the Proceedings of the National Academy of Sciences, biologist Soojin Yi reports that the rate of human and chimp molecular evolution – changes that occur over time at the genetic level – is much slower than that of gorillas and orangutans, with the evolution of humans being the slowest of all.

As species branch off along evolutionary lines, important genetic traits, like the rate of molecular evolution also begin to diverge. They found that the speed of this molecular clock in humans and chimps is so similar, it suggests that certain human-specific traits, like generation time, began to evolve one million years ago - very recently in terms of evolution. The amount of time between parents and offspring is longer in humans than apes. Since a long generation time is closely correlated with the evolution of a big brain, it also suggests that developmental changes specific to humans may also have evolved very recently.

In a large-scale genetic analysis of approximately 63 million base pairs of DNA, the scientists studied the rate at which the base pairs that define the differences between species were incorrectly paired due to errors in the genetic encoding process, an occurrence known as substitution.

"For the first time, we've shown that the difference in the rate of molecular evolution between humans and chimpanzees is very small, but significant, suggesting that the evolution of human-specific life history traits is very recent," said Yi.

Most biologists believe that humans and chimpanzees had a common ancestor before the evolutionary lines diverged about 5-7 million years ago. According to the analysis, one million years ago the molecular clock in the line that became modern humans began to slow down. Today, the human molecular clock is only 3 percent slower than the molecular clock of the chimp, while it has slowed down 11 percent from the gorilla's molecular clock.

This slow down in the molecular clock correlates with a longer generation time because substitutions need to be passed to the next generation in order to have any lasting effect on the species,

"A long generation time is an important trait that separates humans from their evolutionary relatives," said Navin Elango, graduate student in the School of Biology and first author of the research paper. "We used to think that apes shared one generation time, but that's not true. There's a lot more variation. In our study, we found that the chimpanzee's generation time is a lot closer to that of humans than it is to other apes."

The results also confirm that there is very little difference in the alignable regions of the human and chimp genomes. Taken together, the study's findings suggest that humans and chimps are more closely related to each other than the chimps are to the other great apes.

"I think we can say that this study provides further support for the hypothesis that humans and chimpanzees should be in one genus, rather than two different genus' because we not only share extremely similar genomes, we share similar generation time," said Yi.

Even though the 63 million base pairs they studied is a large sample, it's still a small part of the genome, Yi said. "If we look at the whole genome, maybe it's a different story, but there is evidence in the fossil record that this change in generation time occurred very recently, so the genetic evidence and the fossil data seem to fit together quite well so far."

[VadeRetro]

Since no one knows for sure except Darwin and maybe Lady Hope, it is equally "historical fact" whether this happened or not, it all depends who's word you want to take.

The Lady Hope story is a published account containing identifiable innacuracies. The identification of "Lady Hope" with a particular real lady was done later. It assumes the story was not simply a hoax.

The author was identified only as a "consecrated English woman", "Lady Hope", but research by L.G. Pine a former editor of Burke's Peerage found no other Lady Hope other than Elizabeth Hope who was adult in the 1880s and still alive in 1915.

This is your idea of a historical fact. A "could maybe with a few changes have happened" event with a "could have been" author who never clearly identified herself. "Historical fact."

In other words, you consult your convenience first and evidence, if any, second when deciding what is fact. Sure you're not a liberal?

[Virginia-American]

I don't believe we are any more closely related to Chimpanzees than any other ape for the reasons I illustrated in my analogies regarding cousins, apples, and kumquats.

So how do you explain the way the ERVs show up in various species of ape, as though there was a family tree with people and chimps on the same branch?

Source

Are you willing to claim that the hypothetical designer is constrained by the rule that any ERV in both new world and old world monkeys must also be in every species of ape, including ourselves?

By the rule that any ERV in both orangutans and gibbons, which live in Asia must also be in every species of African ape, including ourselves?

If the hypothetical designer is constrained by the rules summarized in the diagram, why? Explain in detail.

If it isn't, then why do we find this pattern?

This is just the primates. The same sort of rules apply everywhere: artiodactyls, carnivores, you name it.

Here is another essay from TalkOrigins with a family tree for artiodactyls; among other things, it indicates that a genetic marker found in both pigs and whales will also be found in hippos and cows.

With all these examples, how reasonable is doubting "common descent"?

[VadeRetro]

This is your idea of a historical fact. A "could maybe with a few changes have happened" event with a "could have been" author who never clearly identified herself.

Apparently, Lady Hope is correctly identified, as this link documents. However, neither of the two versions of her story look anything like "historical fact." Her fellow evangelist James Fegan, who knew Darwin far better, did not believe her story.

[longshadow]

This is your idea of a historical fact. A "could maybe with a few changes have happened" event

It's truly amazing the things that can become "historical facts" under this sort of flexible definition of reality. In that sense, the assertion that the Lady Hope - Darwin recantation fable is true has about the same validity as claims that, based on "hanging chads" and "rigged" butterfly ballots, Al Gore actually won the 2000 Presidential election.

IOW, what you are witnessing is the sort of "flexible epistemology" so frequently employed by Losers on the Left, who can't accept the fact that the public rejects their fantasy version of reality. The anti-Evo "warriors," waging le guerre savage against the "evils of Evilootion," use the same technique, and for the same purpose.

[Ken H]

The Lady Hope story-- fake but accurate. < /D. Rather>

[TheBrotherhood]

>So what you are saying is that anyone who disagrees with you is inherently wrong.

No.

I welcome an open and free exchange of ideas and opinions.

[TheBrotherhood]

All excellent points you make there, RunningWolf.

[VadeRetro]

In Soviet times any tendency to ignore political convenience for accuracy was denounced as "bourgeois" ethics.

[TheBrotherhood]

The quote was taken from a long article and I quoted the pertinent part, not the entire article. But there are no modifications to the quote - it's verbatim as I found it. Did you expect me to quote the entire article? If I quote a paragraph or part therof from a book, by your logic it's an edited quote since I did not quote the entire book.

[TheBrotherhood]

therof = thereof

[VadeRetro]

You cited a quote that a scholar named Moore concluded a visit occurred as the evidence that makes "Darwin recanted on his deathbed" a historical fact. You selectively and with absolutely jeering dishonesty omitted:

1. ... that the visit having happened is but one man's opinion,
2. ... that the overwhelming preponderance of opinion (and the opinion of the AiG article) is that Darwin did not recant,
3. ... that the very same article notes a distinction between the claims of Lady Hope's story and Darwin actually recanting his theory.

You, Sir, are not only a liar but a painfully obvious liar. A particularly bad dancer of the Dummy Dance of Creationism. F- and dismissed.

[RunningWolf]

You declare him a liar on your three points. And 66% of those based on opinion, and the other 33% a distinction??

Sigh.. What shall I say about your grading, your judgment Retro? Well I shall say nothing because I choose not too.

TheBrotherhood is still there, despite your dismissal.

Regards,

Wolf

[StACase]

From your source:

All branches after the insertion point (to the right) carry that retroviral DNA - a reflection of the fact that once a retrovirus has inserted into the germ-line DNA of a given organism, it will be inherited by all descendents of that organism.

These four constitute the argument:

ltr21q22.3
ltr41
ltr32
ltr21q22.2

There aren't any notations for retroviral DNA on the branch between chimps and humans, so claiming humans more closely related to chimps than Gorillas isn't supported by your chart.

The classic primate "family tree" excluding a few early branches looks like this:

Your source would split out the Orang and Gibbon, but that's not the way he drew it. Which leads me to believe he is pushing the humans descended from chimps* button as hard as he can.

*And he'll get around to bonobos in due time.

[hail to the chief]

Except that if anyone disagrees with you, you state that they are not "pertinent and relevant questions," and that they are trying to keep you from being "in focus and on target."

[hail to the chief]

Those three points do not place the burden of proof on VadeRetro. It is the responsibilty of TheBrotherhood to make accurate statements, especially when claiming to be supported by "historical fact," and to admit it when he is caught bald-faced lying.

[CarolinaGuitarman]

The Brotherhood still hasn't produced any source that actually says that Darwin was on his *deathbed* when he allegedly met *Lady* Hope. All accounts have the possible encounter happening in October, 1881, yet Darwin died in April, 1882. He didn't get sick until December, while traveling in London for the holidays (hardly *bedridden*). The attack passed quickly, and he wasn't bedridden until April.

But, because HE said it, it must be a fact. When he passes on someday, we can all make up stories about how we heard him recant creationism and how he renounced God to become an atheist. Anybody who ever met him could say this, and it would have the same credibility as the *Lady* Hope story would.

[VadeRetro]

You declare him a liar on your three points. And 66% of those based on opinion, and the other 33% a distinction??

You and Bro-hood are claiming "historical fact." 66% of your evidence is one man's opinion (that only the first basic step of the story, a meeting, happened). 33% of your evidence is ignoring the difference between what Moore believes can be shown and "Darwin recanted his theory."

A historical fact is a thing for which you have abundant positive evidence.

[Virginia-American]

There aren't any notations for retroviral DNA on the branch between chimps and humans, so claiming humans more closely related to chimps than Gorillas isn't supported...

You're right, I was interpreting the top ones as being common to us and chimps, but it isn't drawn that way.

Here's some of a PUbMed article:

The morphological picture of primate phylogeny has not unambiguously identified the nearest outgroup of Anthropoidea and has not resolved the branching pattern within Hominoidea. The molecular picture provides more resolution and clarifies the systematics of Hominoidea. Protein and DNA evidence divides Hominoidea into Hylobatidae (gibbons) and Hominidae, family Hominidae into Ponginae (orangutan) and Homininae, and subfamily Homininae into two tribes, one for Gorilla, and the other for Pan (chimpanzee) and Homo. Parsimony and maximum likelihood analyses, carried out on orthologous noncoding nucleotide sequences from primate beta-globin gene clusters, provide significant evidence for the human-chimpanzee tribe and overwhelming evidence for the human-chimpanzee-gorilla clade....

Here's another diagram, using molecular clocks

And here's another take

Original caption:

Maximum likelihood phylogenetic tree of human, chimpanzee, bonobo, gorilla and orang-utan Xq13. Reprinted with permission from Nature Genetics (Kaessmann et al., 2001).

Obviously I don't have permission...

I believe the length of the branches represents the genetic distance, although the article doesn't say so.

If this last one is close to the truth, I'd say that we're equally related to Pan troglodytes and P. paniscus

[Virginia-American]

The "classic" tree is clearly invalidated by the evidence. EG, it doesn't group us, chimps, and gorillas together, whereas every source I looked at did, like the PubMed I quoted above which described the evidence for it as "overwhelming".

The "classic" is based on morphology only, I imagine, so that the hairy apes are one group and we're another. But the DNA says something else entirely.

Thanks for pointing out my oversight; researching the last post was quite informative.

[StACase]

Thanks for the reply. I am much more skeptical than you when it comes to this stuff. I just "know" there's politics behind the "findings" after all, there is behind most everything. Data that doesn't point towards the target result is open to be revised, rejected, fudged or ignored. This most certainly went on with the EPA study of 2nd hand smoke. I'm sure Global Warming is another. Innate homosexuality another. It's a long list. How about Attention Deficit Disorder Syndrome? Do you buy into that one? Dan Rather and his minions are not limited to the newsroom you know. Academia has its share of liars, grandstanders, and phonies.