Why did other forms of ancient man die off, such as Neanderthal, Denisovans and Heidelbergensis?
MY THEORY: It was not disease and warring. It was breeding opportunity.
I believe in ancient days, man could mate with a huge range of divergent types of human, Neanderthal, Denosovans, Heidelbergensis and others. This was because man was on foot, far apart, smaller populations, traveling, and they needed to spread the seed.
It is my view that, as man settled into agriculture and communities, they bred without that group - creating races. But also losing the ability to mate with a divergent human. Neanderthal, Heidelbergensis, and Denosvans no longer could spread seed among the modern hybrid humans emerging and "purebreds" of their category ran out of breeding population, being only able to breed within their own kind. A window of cross breeding to ensure population growth closed down. This might be similar to the ability of a horse and donkey creating a mule which is almost always infertile.
In fact, early homo sapien females might have been able to accept seed from any divergent male, mixing their DNA with ours. But, it might not have been the way for Neanderthal, Heidelbergensis or Denosovan females. In that case, those lineages would have needed to mate with their own kind, giving them less chance of running into their own kind and creating more of their lineage, given the spread of early man over the landscape with small populations.
The interesting thing about this is that the mixing of different lineages actually introduced strengths, like immune systems from Neanderthal. We see that today among races; the more races mix, the less they have repeated defects dominating their gene pool. In order to survive, man must keep mixing it up. The result of that eventually will be the loss of races, but a genetic mix that carries a little of all the races.
In essence, the way that Denosvans, Heidelbergensis and Neanderthal continued on was in the hybrid mixes they created. Their lines of early human fell by the wayside if they interbred only with their own kind. Nature forced a hybrid situation to survive and carry genetic diversity and strengths. Perhaps it was the very feature in our homo sapien breeding that allowed for diversity in mating allowed for strength in the genes. More and more issues became recessive or skipped generations rather than being a dominant trait that could kill off a people.
We continue to breed with other races among our own genus and adding diversity. We are losing more and more pure bloodlines of races as Neanderthal and others did not remain in their purebred form. Eventually, races will no longer be and man will evolve into something with immense diversity. It might become the thing that more and more factors are recessive and less are dominant.
So, this is a mind fuck concept for today -