quote:
...either decided to kill off ALL of the prior, less advanced, hominids (ie survival of the fittest as implied above)...
Decided didn`t necesarily come into it bud, think of it this way you and your family cohabit an area with some primitive hominids, due to limited resources for your family to eat the "primitives" must go hungry and vice versa....
Would you let your family starve to death so that the "primatives" would survive?
I suspect not and if so you haven`t decided to go out and kill them in person but by using the available resources to keep your family alive you got them just as dead.... And on a large enough scale just as extinct....
(Of course if they were fitter they would take the food and your lot would go extinct.....)