Controversy: human settlement of the Americas by Clovis culture
* Feder 2006 104-105
"Not all archaeologists are convinced that there was a human occupation of the New World before the Clovis people. Objections have been raised concerning the dating of many of the sites, and it has been suggested that some are not sites at all, but natural deposits. This uncertainty merely reflects the way science works. We must apply a skeptical approach, demand high levels of proof, but be ready to revise our hypotheses if and when our challenges have been met, our objections responded to, our questions answered, and our skepticism soothed. Patience and skepticism are virtues in science." [references omitted]
* Wells 2002 p139-140
"The picture that seems to be emerging from the genetic analysis of Native Americans is that of a migration by the Siberian clan from southern to eastern Siberia within the past 20,000 years. This initial move established a population at the north-eastern edge of Asia. Adapted to a hunting life on the central Asian steppes, they would have subsisted almost entirely off the large mammals of the far north -- musk ox, reindeer and mammoth among them. Consummate hunters, with finely crafted microlith tools, portable dwellings and clothing capable of withstanding the intense cold, these well-adapted tundra dwellers would have gradually extended their range eastward. As the ice age moved toward its lowest temperatures, and more moisture became tied up in the ice caps, sea levels would have dropped by over 100 metres. This would have created a land bridge in Beringia, between Siberia and Alaska, of ice-free land formerly submerged in the Bering Sea. The Siberian clan would have been able to move back and forth across this connection, living a dual Asian-American existence.
"However, these first Americans of 15-20,000 years ago had one more obstacle to overcome. They would almost certainly have been barred from southward expansion by a continuous sheet of ice that covered most of northern Canada and eastern Alaska. It was only as the ice age began to abate, after 15,000 years ago, that it would have become possible to transit the formerly icy interior and enter the North American plains, perhaps via a so-called 'ice-free corridor' that some palaeoclimatologists believe ran along the eastern edge of the Rocky mountains. It is around this time that grizzly bears first enter North America from Siberia, showing that humans weren't the only species to have been stopped by the Alaskan ice. So, the genetic age of 20,000 years, as well as climatological considerations having to do with the extent of glaciation and sea levels, provide an explanation for why we don't see archaeological remains in the Americas before this time. While archaeologists may someday discover a site that pre-dates 15,000 years ago, the mass of evidence is now in favour of a relatively late entry to the Americas. The stones and bones seem to agree with the DNA."
* Calvin 1990 p111-112
"The first American population explosion likely came from those hunting bands that found their way down the ice-free corridor. Or maybe it was the second or third, since there is a lot of argument over whether there were some human inhabitants in both North and South America during the last quarter of the last ice age, more than 31,000 years ago. Like the Vikings who explored the Atlantic coastline centuries before the southern European explorers came and stayed (and attracted the even later but more prolific English), so the earliest human occupation of the Americas may have been a multistep affair.
"Because the corridor east of the Rockies was open before 30,000 years ago, an earlier Bering Strait emigration from Asia could, conceivable, have initially populated the rest of the Americas. But the door closed on the corridor 30,000 years ago, and didn't reopen until about the time of the Clovis hunters, 11,800 years ago. Of course, the early South American populations presently dated (these numbers are forever being updated, and the radiocarbon dates recalibrated) earlier than 31,000 years might also have arrived by boat from the Pacific islands. Everyone is eagerly awaiting enough bones and cultural artifacts from the early sites to make comparisons to ancient populations of the Asian mainlands that spread into the Pacific islands.
"The present-day natives of North and South America seem fairly closely related, just what one might expect from a population explosion based on some initially successful hunting tribes pouring through ice-free corridor. Whether or not some humans arrived even earlier, the hunters seen starting at about 11,800 years ago were prolific big-game hunters and left their Clovis-style arrowheads and spear points all over the continent, including in the rib cages of some now-extinct species of megafauna."