It's a little more than looks, randman. They didn't progress to the kind of tool use and other advanced things modern humans did. But there is a controversy about how different they actually were.
You seem to be making the same mistake here as casebro. See my reply to his post on the bottom of page 2.
This is incredibly incomplete. The genetics of inter-population mixing is very complex, and often includes a number of selection pressures which favor specific genes and not others; to say it's a simple mixing or washing-out is the equivalent of sumarizing Romeo and Julliet as "Two teenagers kill themselves".
There are many. In industrialized countries women are giving birth later than they used to, which is a huge selection pressure. Modern medicines are another, as are modern diseases. The modern diet is something of a selection pressure (given that it's not quite what our Neolithic ancestors ate). Fashion and supermodels demonstrable create a sexual selection pressure. There are a lot more, but I think that proves the point that humans are not immune to selection.
It's no different than the fact humans who migrated out of Africa developed light colored skin. It's just that since modern humans migrated, we've continued to interbreed. So we are all of African descent and so were Neanderthal ancestors.
Fixed that for you. This is allopatric speciation, which is one of several methods, and speciation CAN occur without isolation (ring species provide an example and a mechanism).
The term "complete and utter bloody chaos" comes to mind. There's really no concensus as to what the definition of species is.
I'm surprised that conclusion was still being drawn as late as 2008. I wonder if anyone in the scientific community has commented on these specific differing conclusions?
