Never made much sense to me. This would require a truly massive human population for a hunter-gatherer economy. There just isn't really any evidence of so many people being around then.
From the link:
In the second report, John Alroy of the University of California at Santa Barbara describes a computer simulation of the end-Pleistocene megafaunal extinction in North America showing that even low levels of human hunting would have driven the Ice Age behemoths out of existence. Importantly, the simulation, which assumes a slow human population growth rate and low maximum hunting efforts, correctly predicts the fate of 32 out of 41 megafaunal species. These findings, Alroy argues, show that in fact anthropogenic extinction was unavoidable. "The overkill model thus serves as a parable of resource exploitation," he concludes, "providing a clear mechanism for a geologically instantaneous ecological catastrophe that was too gradual to be perceived by the people who unleashed it."
I never heard of it before either. Never get surprised by a Malthusian with a computer model.
All I can say about this is “DUCK!”