You are, of course, correct that there are a number of possible explanations for modern humans out-competing the Neandertals, besides the obvious one of us killing them.
The absence of Neandertal male DNA in our own ancestry makes it less likely the process was peaceful, though. That’s exactly what you find in those areas where historically we know the invaders killed all the males and kept some or all of the women.
My point was how often anthropologists jump to the conclusion the replacement of one species or race was peaceful, when there is really little evidence either way. It’s obviously what they want to believe.
BTW, if we’re interfertile with Neandertals, are they really a separate species? Maybe they were just lost Klingons.
Maybe the reason why non-African populations are only 1-4% of Neanderthal ancestry is that there would be enough inversions to make a hybrid have fertility problems.
Neandertals were different enough that they would, by most zoological standards, count as a separate species, but certainly a ‘cousin’.
Modern day coyote populations are of some 5% (IIRC) wolf ancestry.
But a wolf and a coyote are obviously not the same species.