The speed of that spread — inferred from both the geographic distribution of Clovis sites and from the genetic differentiation between North and South American populations — was remarkable.

People moved from Alaska to the southern tip of South America in what geneticists estimate was approximately 1,000 to 2,000 years.

That is an extraordinary rate of geographic expansion by any standard, and it speaks to both the extreme abundance of resources in a continent that had never been subject to human hunting pressure and to the mobility and adaptability of the founding population.

The Anzick child was born approximately 12,600 years ago in Montana — which places him at the leading edge of this southward expansion, or shortly after it.