The fact that we have proof that interbreeding occurred between Sapiens and Neanderthal should open the possibility that they quite simply were blended into a larger Sapiens population instead of mysteriously disappearing.
Sapiens are Neanderthals.
One thing we're very confident in is that anatomically modern humans (i.e. us) are not neanderthals.
[0] https://en.wikipedia.org/wiki/Computational_phylogenetics
We’re not neanderthals, but they are largely no longer considered a separate species. Neanderthals are now commonly known as Homo sapiens neanderthalensis in the literature. Their genetics are not that different from sapiens and the difference is only about twice as much as the variation in the global gene pool so they’re more an extinct branch of a much more diverse species which suffered a genetic bottleneck leaving only us.
The most striking example is from the Taï forest, where the 19 haplotypes show greater diversity than the entire human clade, even though they occur in a single breeding group.
I believe that the idea of blending by peaceful interbreeding is just wishful thinking based on modern ethics.
Some Neanderthals have probably blended into modern human tribes, most likely some children or women. Other hybrid humans may be the result of random encounters.
The majority of the Neanderthals have disappeared during a relatively short time span, of a few thousand years. Some of them might have died as a result of direct fights with the expanding modern humans, the others might have been forced to retreat into worse territories that provided less food, so their population has dwindled.
Mexicans are roughly half Native American, half European.
>The majority of the Neanderthals have disappeared during a relatively short time span, of a few thousand years.
People did something that killed off the megafauna, and made people deformed at the same time. Genetically we are one species.
After most conquests, which have established a new ruling class in some territory, there has been a mixing between the former invaders and the previous native population.
In many cases, the former invaders were less numerous than the natives, so after a few generations the mixed population has begun to resemble more the previous natives than the new incomers.
Nevertheless, I do not consider that these are examples of peaceful blending. In all cases the original war has inflicted serious losses on the natives and the reason why in more recent times no more of them were killed than necessary was because they were needed as a work force.
Before the organized states, which were able to tax the work of everybody, and before the use of slavery, there were no reasons to keep alive any vanquished tribe, which would compete for the food resources of the territory.
The losers would have been forced to run away to other territories, to stay alive. Except perhaps for women and children, they would have never been adopted by the victorious tribe, to blend in it.
I don’t see stephc_int13 writing anything about the peacefullness or non-peacefullness of the blending.
So it's entirely possible that Neanderthals were assimilated into Sapiens tribes.
What I am suggesting is that Sapiens won by numbers, that they were more numerous.