(snip) I believe the "out of Africa" theory gains support from the wish to stress the complete separation of modern humans from other animals and even earlier humans. Darwin's contemporaries had trouble understanding how advantageous characteristics could expand through a population. They had no knowledge of DNA, let alone genes. So when the economic term "survival of the fittest" was coined in economics it was seen as an explanation for the problem and rapidly taken up. Obviously many people are still stranded in victorian ideas of how evolution works as TheFallibleFiend and I are trying to explain elsewhere.
I disagree. "Out of Africa" gains no support from any wishful thinking on the part of people who already accept evolution as the best theory we have for species diversity. Keep in mind that it was first assumed that Neandertals and many other pre-human primates were in our direct lineage. Also keep in mind that researchers in mtDNA studies of Neandertals and humans start with the assumption that there was interspecies sex.
Personally, I'd believe or disbelieve that Neandertals are in our relatively recent lineage based on hard evidence. So far, the evidence leans toward no interbreeding with Neandertals.
It is inconceivable that the various regional varieties of ancient humans didn't form hybrids as they moved around, exactly the same way as the greenish warblers in Asia mentioned in the link. The authors exagerate when they say "that few examples of such species are known today". Great tits, herring gulls and various species of deer are other examples that I immediately think of.
Samwik. Chimps and bonobos are hardly separate species. They readily form fertile hybrids. The ancestors of chimps and humans formed hybrids for more than three million years before they finally separated.
When you're talking about small populations seperated for long periods of time, there might not be a lot of opportunity for interbreeding. Also, the fact that you can produce fertile, interspecies crosses in zoo or lab environments does not mean these crosses will happen in the wilds. Bonobos
are different species than chimps. They behave quite differently, which probably is the reason you don't see hybrid populations or mixed populations between bonobo and chimp habitats.
Sorry to burst into the middle of a conversation. You may have already gone over this stuff. If so... sorry.
