If the population of humans and chimps bottlenecked at the same time as is plausibly presented in the linked Toba article, then perhaps the chimps managed to have a couple of populations that had previously diversified come together with less territorial pressures. perhaps the chimps had a few more paternal figures that added their genes to the mix (and actually differences in monogamous human versus chimp opportunistic mating behaviors make it quite plausible that a diversified group of male chimps passed their seed versus a very narrow selection of human males). Perhaps humans killed of each other, or perhaps there was a scenario that fits the stereotypical Amazon women tales where they killed off all the men except for one who then impregnated them all. Perhaps any of these, or a million other scenarios or situations that might explain it.
We do not have sufficient evidence to explain why our bottleneck only allowed a few variants through, while chimps may have had more, and when the sample size is reduced substantially even extremely slight variables can make a dramatic difference in potential outcomes.
Last edited by marduc; 07-07-10 at 03:00 AM.
News in Science - Early humans had sex with chimps - 18/05/2006
I haven't followed up on it much more than these few articles...other then the genetic diversity part.
From your article:
So our common ancestor was able to interbreed for a while before the two populations split into what became chimps and humans, This is how speciation works, eventually the changes add up to the point where they can no longer interbreed, and they become divergent populations that continue to drift further apart over time."It is possible that the Toumai fossil is more recent than previously thought. But if the dating is correct, [it] would precede the human-chimp split," he says.
"The fact that it has human-like features suggest that human-chimp speciation may have occurred over a long period with episodes of hybridisation [inter-breeding] between the emerging species."
A gradual divergence of species through hybridisation, rather than a quick break, may be far more common than we suspect.
Last edited by marduc; 07-07-10 at 03:15 AM.