Well I'll Be A Monkey's Uncle

killproc writes "A new report suggests that interbreeding between humans and chimpanzees happened a lot more recently than was previously thought. The report, published in the most recent issue of the journal Nature, estimates that final break between the human and chimpanzee species did not come until 6.3 million years ago at the earliest, and probably less than 5.4 million years ago."

Comments

Misleading

[Reckless Visionary]

What this shows is that there was likely interbreeding between the ancestor line of humans and the ancestor line of chimpanzees. Unfortunately, all the headlines I've read skip that distinction and dive right into "humans and chimps interbred." They were not either modern humans or modern champanzees, and were likely much closer in genetics and appearance than we are to modern chimps, even though even now we are very close genetically after 5 million years of divergence.

Re:There won't be any controversy here!

[pe1rxq]

You mistake in the way you think about selection.

There is no 'law of evolution' kind of thing that says that a species will involve into something more complex or intelligent.
Natural selection simply works because a certain species is capable to stay in existence.
Sometimes being stupid and just breed is more efficient than being intelligent.
Ants have a complex structure which allows them to spread very efficiently. Knowing how to paint for some reason wasn't needed for them to spread widely and thus such an feature would only result in extra lugage to carry around.
Maybe out species at some point managed to stay alive longer by being a little bit more creative than our cousins. That might have been an factor that resulted in more offspring.

Jeroen

Re:There won't be any controversy here!

[gowen]

why the need for art and culture

What makes you think there's a need for art and culture? Humans didn't evolve a desire art anymore than kittens evolved an enjoyment of playing with wool. It's the vestige, an accidental by-product, of some things we did find evolutionarily advantageous : intelligence, language, society and imagination.

Re:Hold it a second!

[Wabin]

Ugh. As a genetecist whose lab does work on this stuff (I personally avoid human data, but do work on speciation), I would say that one of the good points Hawks makes is that there is a lot of work that should have been cited that wasn't. They present their paper as if they are the first to suggest that there was a period of human-chimp hybridization. I won't go into the older literature, some of which they do cite, but more recently, Navarro and Barton (2003) (link may be behind paywall, sorry) provided some evidence for extensive hybridization. Also, Osada and Wu (2005) (which is cited, but really really strangely) were more explicit in their claim of hybridization (though here they refer to it as disproof of pure allopatry (a rapid event driven by geographic isolation)). Some of the methods in the "new" paper appear to be directly derived from tests in Osada and Wu. The work itself is good, but maybe not as groundbreaking as they would like to believe. Personally, I was just waiting for a good data set to come up with better evidence for something I was quite confident of already. This does that.

I also happen to think that as we investigate more and more pairs of close species, we will find this is not at all an uncommon pattern. There are lots of hybrids out there in nature, and you can be sure that genes make it across "species boundaries" with some regularity for quite a while.

One final note to destroy my credibility. Is anyone surpised that people had sex with chimps? (Okay, proto-humans with proto-chimps) We are a couple of horny species. I don't know too much about chimp sexual habits, but we humans sure are a kinky bunch to boot.

Re:There won't be any controversy here!

[plunge]

Ok, well, then the answer is simple: they're lying.

First of all, by all respects, positive mutations in practice DO happen, and indeed one can point to any number of recent examples just in humans, just recently. Tetrachromaticism in women is recent. So is the immunity to the negative effects of LDH cholesterol developed in a single man in Italy (creating descendants among whom heart disease and strokes are vanishingly shockingly rare).

Second of all, think about it logically. Mutation is random. That means that anything it can do, it can undo. So if it can have bad effects, then it can also have good effects (for instance, if one mutation breaks something by changing a T to an A, then the next mutation can change the A back to a T, thus having a positive effect).

Thirdly, creationists generally also admit that mutations can cause observeable variations in a species: longer beaks, shorter legs, etc. But any of these can have positive effects, so they've just unknowingly admitted to something they elsewhere deny.

Finally, talking about mutation and function in this way is itself misinformed. Whether or not a mutation is "beneficial" or not depends a great deal on context. A particular mutation can have a negative effect in one context, and a positive effect in another one. There are certainly mutations that very clearly are better or worse than what came before in all contexts, but by and large there is no objective measure of whether a mutation is beneficial, neutral, or positive. It all depends on a lot of other factors and how it plays out.