Neanderthals were BRED to near extinction via a phenomenon which we call
"erocide" -- the destruction of a people incidental to genetic
encroachment typically involving de facto polygyny and differential male
fecundity between the gene-pools.
In the case of the neanderthals, it is plausible that their males, when
coupled with gracile females, would produce fewer live births due to the
narrow birth canal of the gracile females. The more gracile humans
emerged from Africa in one of the earliest erocidal gene-flows from that
area, through the Levant, north and west through europe.
Another aspect of erocide is that the encroaching gene-pool, for obvious
reasons, avoids violent confrontation and seeks friendly integration.
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The promotion of politics exterminates apolitical genes in the population.
The promotion of frontiers gives apolitical genes a route to survival.
Change the tools and you change the rules.
If some mitochondria-related disease affected humans, this could give a
false picture of the evolution of the race.
Before the corn blight spread north, the majority of the corn crop
shared the male sterile mitochondria, suggesting (to the unsuspecting
observer) that the various races of corn (flint, dent, sweet, pop, etc.)
were derived from the same male-sterile Eve.