Most of my info on the subject comes from a
history book by Charles C. Mann i read about New Revelations of the Americas Before Columbus and some from books i've read by Richard Dawkins.
both are disputing the history of America on lots of points, from the land bridge theory to underestimates of the small pox epidemic.
Mann even contends De Soto intentionally brought the virus with him kept alive in pig stock for the purpose of weaponry and it swept coast to coast killing tens of thousands at such a speed they could not bury the dead for dying themselves and that its dramatic effect was due to different genetic susceptibility of the Amerindian.
Manns contention and premise for the book is we have it all wrong.
and even as i Google the subject their are lots of major discrepancies like the 13,000 year date of the presence and the 20,000 year carbon dates.