Weird Fantasy #17

In the future a space crew go through a time rift and land on a prehistoric twin Earth. They are attacked by some ape men. They capture three and manage to return to their own time period. The ape men are put in a cage and are studied by experts. When one of the ape men falls ill (a female), a scientist warns that if it isn't returned to the past, it could effect the whole evolution of man. The captain refuses to risk looking for the time rift again, and its decided to let the ape man die. This causes the human race in the present to vanish and evolution to begin anew.