For many years, scientists have thought that the first Americans came here from Asia 13,000 years ago, during the last ice age, probably by way of the Bering Strait. They were known as the Clovis people, after the town in New Mexico where their finely wrought spear points were first discovered in 1929.

But in more recent years, archaeologists have found more and more traces of even earlier people with a less refined technology inhabiting North America and spreading as far south as Chile.

And now clinching evidence in the mystery of the early peopling of America — Clovis or pre-Clovis? — for nearly all scientists appears to have turned up at a creek valley in the hill country of what is today Central Texas, 40 miles northwest of Austin.

The new findings establish that the last major human migration, into the Americas, began earlier than once thought. And the discovery could change thinking about how people got here (by coastal migrations along shores and in boats) and how they adapted to the new environment in part by making improvements in toolmaking that led eventually to the technology associated with the Clovis culture.