Then, just as everybody was getting cozy, 12,000 years ago a comet hit mid-continent and busted up the residual icesheet in Canada.
We find the debris all over the American midwest.
The ice flows down the St Lawrence valley increased flooding the North Atlantic with ice. This triggered an almost instantaneous return to deep Ice Age conditions.
1500 years later that ice melted and the interglacial climate continued on to where we are today ~ 5,000 years overdue for the next glaciation.
The Mastadons dining on grass and other herbacious delights died out rather quickly with nothing to eat. Their predators also died out.
With the big cats out of the way both North America and East Asia were opened up to human settlement.
There is no evidence the mammoths went in one big blast or any impact caused any long term or global impact.
All these big animals went extinct over an extended period of time. What shows man did it was the last remaining populations of these animals were in the remote areas where man was last to show up.
So either man did it or by an amazing coincidence where ever man showed up the climate changed and a comet hit.
My goodness, these scientists are finally discovering that Firestone and company were right after all.
Next thing you know they might even starting looking underwater for evidence of well developed civilizations long before the Egyptians and the Sumerians