Why would this be such a heated question? I know Native American groups like to think of themselves as the original Americans, but that surely shouldn't cow serious researchers. Then there is the ever-intriguing question of why civilization arose where it did, and why, with the Americas and sub-Saharan Africa noticeably lagging. I had the notion that relatively short habitation of the Americas functioned as something of a mitigating factor. Jared Diamond made a splash awhile back with Guns, Germs, and Steel (which I never found very persuasive), but I've not read enough of the literature to comment with any confidence. So: why is an earlier human presence in the Americas a touchy subject?
Mr. Diamond made a pretty persuasive case if you substitute”influenced” for “caused.”
“So: why is an earlier human presence in the Americas a touchy subject? “
If whomever these earlier humans were are not the genetic ancestors of the current “native Americans” it would weaken their claim to being the original indigenous peoples of the New World. Or so I’ve heard.
Because a whole bunch of people wrote dissertations saying that they had only been here a few thousand years.
Once the scientific community has formed their "consensus" then anyone trying to say different has a tough row to hoe.
And most of time the consensus comes from people inventing a story and trying to fit the evidence into it.