As a big fan of ERB, I have to tell you that we should all be so lucky as to have mankind “act like Tarzan”; i.e. as a responsible steward of the wild.
Whatever the logistics of extermination of megafauna with stone tipped weapons, the disappearance of many different species of mega-fauna over many different lands- that just happen to coincide with human habitation - seems to indicate that it really might not have been so difficult as you imagine.
Perhaps they were on the way down when we decided to make tools?
Early man didn’t focus on mega fauna other than to scavenge what remained.
Again I’ll pose: if the lethality of sticks and stone were not in question, how then did mega fauna survive the human onslought in other continents?
I can’t blame Bush-men ;) :p
I was a big fan of ERB and my favorite series was the Moon Men etc... Julian I-9