One would beg to differ.
1. Absence of evidence is not evidence of absence.
“No...there were no Neanderthals in the Americas.”
2. A negative cannot be proven.
Hypothesis: If there were no Neanderthals in Americas, from whence did the 50% gene factor originate?
Asia?
Australia?
Hawaii?
Would there not be 50% factor remaining in Asia somewhere?
[Hairy Ainu?]
Or did the Asian 50% factor die out too, in Asia and left Amerinds orphans on a new continent(s)? or was the 50% diluted by interbreeding in Asia?
3. Or did the Proto-Europeans cross an ice/land/sea/boats bridge from the northern European shores to Americas inbetween Ice Age glacial flows?? [AHA! Did Neanderthals know how to build a boat???]
4. Do Canadian, USA and Greenland eskimos have the 50% gene factor?
well duuhhhhhh
Well, First nation people just gotta know, ya`know
or they just can`t sleep at night not knowing what the hell happened to their 50% way back when...
Merry Christmas!