Humans and monkeys: Recent convergent evolution on COX2?
Svante Paabo’s group just finished sequencing the complete mitochondrial DNA of a Neanderthal. The article is in the newest Cell. John Hawks has a summary.
One of the big findings: In one tiny way, we’ve become more like monkeys recently, since Neanderthals, chimps, and other sequenced apes have the same non-homo-sapiens variants on COX2, but these human variants are common among old world monkeys. Guess I’ll have to take my pet macaque off of Vioxx now.
Upshot: Something big may have happened to human metabolism in the last few hundred thousand years since our split from the Neanderthals. And on this one gene, the solution our species found looks like the same solution that works for monkeys.
for everyone with poor reading comprehension like myself, that’s the mitochondrial genome, not the nuclear genome!
it might be useful to catalog these sorts of relationships which refute the great-chain-of-being assumption which lay at the heart of many peoples’ understanding of evolution….
How improbable would it be for a species that split to converge enough that they would be able to interbreed again after a period in which they couldn’t?
seems conditional on the isolation mechanism. seems like what you’re proposing might be viable for prezygotic isolation (e.g., species begin to interact again in their niches as they converge), but less so in postzygotic.
Could the the extinction of the neanderthals be due to interbreeding with humans creating nonviable hybrid offspring?
I would imagine during those winters in northern Europe the neanderthal males would be pretty popular due to their high tolerance to cold temperatures.
able to interbreed again after a period in which they couldn’t?
Seems damned unlikely to me. It normally takes quite a bit of divergence to make interbreeding impossible (witness the fact that lions and tigers can still produce offspring). I suppose we could imagine a case where one very dramatic mutation made interbreeding impossible, so that mere reversal would accomplish the feat, but in the general case I think it would not happen.
might be viable for prezygotic isolation … less so in postzygotic
Considering that the definition of prezygotic isolation includes things like the Andaman Islanders, I’d say that we have plenty of examples of the former already – but I don’t think that’s really what TGGP was asking about.