Ancient man must have been like ants covering the whole of the earth.
Indeed. They were also very fat from eating every animal they found and so, eventually, became too fat to hunt any longer, which lead to the extinction of ancient man.
This extinction was aided by the dearth of very large game, and lead to the inevitable cannibalism, which in turn left few bones of ancient man to be found by industrious PHD types, which in turn lead to a huge rise in speculative activities by said PHD types in search of grant money so they too could become very fat.