Occam's Razor says there's a simpler explanation. The Indians ate the mammoths, the mastodons, the giant sloths and armadillos. The sabertooth tigers starved. You don't need superheated hurricanes, supernovas firing interstellar shrapnel, etc. And how come this supernova weather didn't hit Asia or Europe or Africa?
But your hypothesis fails to explain why similar large animals continued to survive elsewhere in the world, i.e. Africa. Why did the elephants there and in Asia survive human predation? Regardless, I think this was some darn fine detective work on the part of these guys.
The muslims were protecting those continents!
Huh! Hadn't read your post when I sent mine -- but good minds think alike.
The problem with the human hunter explanation can be found in Southern and Southeastern Asia where the elephant and tiger as well as large apes, etc. survive beside rather large and culturally highly developed human populations. Still questions. Personally, I doubt any one answer will suffice. Certainly climate change -- global warming without SUV's if you will -- is part of the answer in the Northern Hemisphere. That along with the spread of humans, that is.
I agree, and for that matter, do the scientists have an explanation for why the ice age glaciers covered nearly half of North America, much of Europe, but almost none of Siberia, when Siberia is colder than the other two places today? I suspect it has something to do with the north magnetic pole being on the Canadian side of the Arctic.