That’s rarely discussed but is a reasonable answer to the genetic data.
Why are there NO Neandertal Y chromosomes or Neandertal mitrochondrial DNA examples in the human population, while the DNA is clearly present?
One answer is that it was selected against, but this is unlikely given the one to three percent Neandertal DNA present in the population. SOMEONE would carry at least one of those if population mixing was going both ways or semi-fair.
An answer could be: Neandertal men saw the stronger neoteny traits in human women (lither bodies, large eyes in a flat face) as attractive and raped them, certainly possible given their greater physical strength. Humans had more variety in tools but were newcomers to the land; some women made it home, carrying a hybrid baby.
Genetic models show that just a few dozen times of this happening very early in the small population of humans who left Africa would account for the genetic distribution of Neandertal DNA.
So what explains the genetics we see, of no Neandertal mitrochondria or Y chromosomes?
The humans knew numbers were small. They killed the sons of Neandertal men, because they didn’t want to raise the rapist’s son. The hybrid daughters they kept, because they needed the breeders, keeping Neandertal DNA in the next generation but only hybrids with human mitrochondria.
In contrast, humans didn’t have a chance with Neandertal women who were far stronger, and/or the few hybrids that occurred that way weren’t cross-fertile or died out with the Neandertals.
I doubt people-Neanderthal from Europe, Homo Sapiens from Africa, Denisovan or whatever-were much different from the primitive tribes that still survive in remote places today. Humans have probably always been curious, loved to trade and coveted the foreign and unusual female.
I doubt the Romans were the first to realize the value of their women as bargaining chips for lucrative alliances with foreigners in mutual defense and trade. And I doubt those women had any more choice in the matter than women in Roman, Greek or Egyptian times did-she still was carried off and forced into having sex with a stranger of another race, tribe, etc, and I don’t doubt rape happened more often than not...