In the book The Sixth Extinction, the author posited that you really don't need very sophisticated or systematic hunting to bring megafauna to extinction. Their

In the book The Sixth Extinction, the author posited that you really don't need very sophisticated or systematic hunting to bring megafauna to extinction. Their strategy for survival is to be large, but at the cost of very long reproductive cycles. Slowly but steadily picking one off every now and then can bring them to extinction over the course of centuries, which at the same time means their slow demise and the cause of it can easily go unnoticed. Megafauna extinction is closely timed with the arrival of humans on just about every continent or island we happened upon. Even Africa is relatively more depauperate compared to the distant past. Of course not all of them found their end. There are still moose in North America, and giant tortoises in the Galapagos that literally floated away from the coast of South America, where they later went extinct. But there are fewer everywhere.