How did all of the megafauna disappear worldwide in a short period? My hypothesis is that ancient man discovered that an atlatl with poison could be launched from a safe 100 yard range at critters large enough for a BIG BBQ. That’s why smaller game, e.g., deer survived and megafauna became extinct. The Aleuts used small harpoons thrown with atlatls from kayaks to kill 40 ton whales. They used aconite from the roots of Monkshood flowers as the poison. Nicotine would work too. A few hundred years of such BBQs and good times would increase the human population manyfold and wipe out animals vulnerable to such hunting techniques.
Just think of the ribs on that puppy.