blended theories

for evolution theories, I was thinking, natural selection is probably just one part of the story. natural environment can change creature's gene, those activities probably will affect creature itself as well(as used gets more, not used gets less), so it could be a blended theory instead of just one.

the other one is about african origin or multiple origin for homo sapiens. could it be possible that a big brand spread around the world, but instead of 'taking over' of everybody, it might have blended with some local home sapiens, like what spanish did in south america, maybe. of course they can be traced back using some gene because they have some common ancestor, they could have an old ancestor which shares the same gene too.