[MonctonRad]

Originally Posted by VANRIDERFAN

There were no modern horses in the Western Hemisphere when humans first crossed the Bering Land Bridge. For some reason the horse went the other way.

I still find it kind of hard to believe that the humans alone wiped out the Mega Fauna. There had to be other mitigating circumstances that contributed to their demise.

From an article in "Science" from 2014:

radiocarbon dates also suggest that northeastern megafauna underwent two major declines before finally going extinct. The first was 14,100 years ago, before any humans were in the region, but the number of animals then recovered after about 500 years; the second and final population crash began 12,700 years ago, when Paleoindians had just arrived in the region, according to the archaeological record. Moreover, the team reports in the 1 February issue of Quaternary Science Reviews, even though humans and megafauna continued to coexist for about 1000 years before the animals finally went extinct, the animals were already on their way out: Between 75% and 90% of the northeastern megafauna were gone before humans ever came on the scene. Yet even during the millennium of human and animal overlap, the team argues, there is no evidence for hunting: Neither megafaunal nor Paleoindian sites in the northeast contained animal bones that were butchered or otherwise modified.

The authors stress that their results can be directly applied only to northeastern North America, and not to other regions such as the Great Plains and Southwest. Nevertheless, given the large amount of megafauna in the northeast, and the lack of evidence for human involvement in their demise, they argue that overkill cannot have been the only or even the major factor for continent-wide extinctions: Climate and environmental stresses must have also played a key role. The timing of the second megafaunal crash, 12,700 years ago, corresponds with the beginning of a major, 1300-year-long cold snap called the Younger Dryas, which was followed by the warming trend (called the Holocene) we still live in today.

Apparently the only megafauna where there is solid evidence that paleoindian overhunting may have had an effect in extinction is the mammoth and the mastodon.