But what about the Aliens when did they come into play?It only suggests that while the great apes originated in Africa, the Hominid that evolved from them did so in Europe and flowed back to Africa. Evolution typically has something driving it, and there was more survival pressure at the edge of the ice fields than in the just another day in Paradise subtropical Africa jungles.
Maybe they formed the ice bridge in an attempt to harbor world peace amongst the Apes.