From what ive seen him/other people talk about the main points he presents that seem plausible to me are that people might have come much earlier to north america as found by the san diego museum which leads to the possibility of human culture developing in the region much earlier alongside the lack of archeological digs deeper in this possible time range. The lack of evidence cannot equal his theories being true obviously but i guess i was hoping that there was more research being done in finding out if this was possible. His other point that seems possible to me related to this is how they might have gotten there with the northern passage way still being used as a possible land bridge and the massive amount of ice that eventually melted over north america due to a possible major impact alongside rising global temperatures. he states that is possible that 100,000+ years ago a passage way in between the two major ice sheets could have opened up as similar increases in temperature have been found to when humans crossed before the end of the recent ice age. When looking at these pieces of data it seems fair that humans could have been around north america for a much longer period of time than currently taught and might be possible to find with current technology. He also discussed the genealogy of some of the native amazonians which have australian dna which I cannot find anything further on other than that is true( https://www.smithsonianmag.com/science-nature/dna-search-first-americans-links-amazon-indigenous-australians-180955976/ ). One quote here makes me think that his idea might be a real possibility "There’s just one problem: Evidence of Population doesn’t persist in modern Eurasian groups, nor does it seem to show up in other Native Americans. If Aleutian Islanders or their ancestors had somehow mixed with an Australasian group up north or made their way south to the Amazon, they'd leave genetic clues along the way. “It’s not a clear alternative,” argues Reich. "