[pierrem15]

Very similar is true but we were almost at the point of biological separation where offspring would have been sterile, like horses and asses. Male human/Neanderthal hybrids were likely sterile due to subtle genetic changes affecting sperm production. This is the usual explanation for why we see no male Y chromosome descendants of Neanderthals in human populations, at least given the samples so far.

[Jim Noble]

This is the usual explanation for why we see no male Y chromosome descendants of Neanderthals in human populations, at least given the samples so far

It's not even that complicated.