We fix that long time not only by dating a few excavations but by a diverse range of concurrent, datable fossil markers, from the bones of extinct saber-toothed cats, cave bears and odd little mice to multiple layers of volcanic ash and pollen, in valley walls as deeply eroded as Olduvai in East Africa. Scores of excavations over that entire wide hemisphere have shown us worked stones, old hearths and skeletal remains, all left by our ancient forebears. They were not yet members of our own species, but they are ancestral kinfolk of our own genus, the hominids, in all those places. Across the Americas we can point out scrupulous excavations in plenty to show who came here to the New World. A score of sites are found from the Bering Sea south to the region of the Straits of Magellan.
None bears any witness to protohumans at all.
All those bison hunters, spearhead shapers and cunning basket weavers whose handiwork and physical remains have been found in these Americas are of our very own kind, that single species we self-servingly dub Homo sapiens. Our living species is proved by long experience to be a single species, fully interfertile. By no means anything like a million years old, H. sapiens might go back a tenth of that time, possibly even as much as a third of it. That order of magnitude carries my point. All over the globe, Old World and New, there are no living hominids save sapiens.