Archaeologica.org

Darwin also suggested that speciation results from a population being "isolated."

I was reading an article earlier Min and that still seems to be the view, but as far as I can see that would depend on what they define as isolation.
Take the scenario I described earlier with a HG group splitting. Their new neighbours are HSN and they are HSS, they interbreed and one group splits, they then move away suffiently far so as to create a new territory. They are isolated from the parent group and when they split in the future the new group will again be moving further away from pure HSS and pure HSN.
Hybridization is the fastest way to create a new species, in the human race, less than 100yrs would be needed.

Minimalist wrote:
Darwin also suggested that speciation results from a population being "isolated."

But were these various forms ever truly "isolated" from one other.

There was a total absence of road and highway systems, ferries, and of course air transportation, in those days – there was NONE AT ALL of that: connections.
A situation like that qualifies as 'isolation' in my book.
If – say, 40,000 years BP – there were a couple hundred thousand HS and a few dozen thousands of HN in Europe I bet 99% of them never even met the other species during their lifetime.

I agree RS. The experts all seem to think an ocean or a mountain range is necessary. In my youth I met people who had never been more than 10 miles from their birth place.
I lived for some years in a tiny village with a group of children all about the same age and I was the only one who went out of the village for a partner.

http://en.wikipedia.org/wiki/Cro-Magnon

The Cro-Magnons must have come into contact with the Neanderthals, and are often credited with causing the latter's extinction, although morphologically modern humans seem to have coexisted with Neanderthals for some 60,000 years in the Levant[5] and for more than 10,000 years in France[6].

Fossil evidence tells us that they must have had contact.

Logically as frequently with HSN as with HSS once they moved close to HSN occupation zones.

Beagle wrote:http://en.wikipedia.org/wiki/Cro-Magnon

The Cro-Magnons must have come into contact with the Neanderthals, and are often credited with causing the latter's extinction, although morphologically modern humans seem to have coexisted with Neanderthals for some 60,000 years in the Levant[5] and for more than 10,000 years in France[6].

Fossil evidence tells us that they must have had contact.

Yes: in the Levant!
But if the subject is extinction of HN, aren't we mostly concerned with Europe here? Europe is 100 times larger than the Levant. With a 100 times less chance of 'running into eachother'.

Besides: does 'they were in contact' mean they met eachother on a more or less daily basis? That they lived sort of side-by-side? In the same locales (valleys, beaches)? Which would be required for merging/hybridization.
I highly doubt that.

If that wasn't the case RS then it would have been the case for HSS as well! If that is so, following the isolation view, there would have been a lot of isolated, inbred, groups.

Digit wrote:If that wasn't the case RS then it would have been the case for HSS as well! If that is so, following the isolation view, there would have been a lot of isolated, inbred, groups.

There were.
And are!
Ever been to isolated mountain villages in the Alps? The ones that don't have direct access to roads and only got (ski) lifts in the last 50 years? Or how about islands, like in the Aegean, or in the Pacific? Or the British isles for that matter?
You only have to keep your eyes open to see signs of more or less inbreeding all over the place there! The "English Rose" is my fav example...

So following the view that isolation produces new species there should be a lot more Homo than there are. Our genetic differences are far too small for there to have been such isolation. HG groups seem to aware of each other's existence and meet as well

Sorry, I've been watching a football game. Most anthropologists believe there was contact between the two groups. There is evidence of trading of technology and tools. Some folks think there were viable offspring and some don't. The Neanderthal Genome project is working on that now. But I think it will take quite a while. I'm betting that Neanderthal DNA will be found eventually.

Digit wrote:I agree RS. The experts all seem to think an ocean or a mountain range is necessary. In my youth I met people who had never been more than 10 miles from their birth place.
I lived for some years in a tiny village with a group of children all about the same age and I was the only one who went out of the village for a partner.

What about people who lived in the border zones, for want of a better word?

At some point, they came together.

Digit wrote:So following the view that isolation produces new species there should be a lot more Homo than there are. Our genetic differences are far too small for there to have been such isolation. HG groups seem to aware of each other's existence and meet as well

Who's genetics are you referencing Digit? I am not aware we have this pool of samples to compare. HSS is 98% identical to Chimpanzee but the differences are obviously significant.

In any case the question for me is, what happened to HSN? If HSS and HSN lived in similar environments and environmental change killed off HSN, why did HSS survive? Unless the two groups were not as closely associated as being discussed. On the otherhand, if it was not environmental, and if the the two supposed 'species' were co-mingling, then perhaps as I believe Beagle has suggested, HSN and Cro-magnon just sort of blended away into modern HSS. A sort of diffusion. Is this plausible? If so, then the whole the question of speciation needs to be revisited in my opinion.

Got to have done Min or there would be about 50000 different Homo species.

The answer to that Monk is that I have no idea at all! I have made the observation before that if you presented a DNA sample of a Mule to a geneticist with no knowledge of horse or ass would he know the Mule was a hybrid.
If we are as close as that to the Chimp we would logically be very much closer to HSN, so you tell me Monk, is my DNA HSS or HSN or both!

Digit wrote:If we are as close as that to the Chimp we would logically be very much closer to HSN,...

This is an assumption mainly based on skeletal morphology and absolutely NO genetic evidence whatsoever. I don't necessarily dispute it. I just point out it is an assumption.

Nevertheless, as Min alluded to a while back, if HSN and HSS were different species they could not produce viable offspring.