Terry, I just have a hard time, personally, seeing our poorly armed primitive ancestors as the "Mighty Hunters" depicted by Hollywood and suggested by those who ascribe to the Mammoth-wiped-out-by-Man Theory.

As for the Killifish, they are extremely ph sensitive, as I recall, and need an alkaline environment. And, at 40mm in length with mediocre swimming ability, the'd be hard pressed to survive very long in NA waters.