Origin: A Genetic History of the Americas

by Jennifer Raff

There are currently several basic models for how, when, and where people first entered the Americas. The most conservative model resembles a new version of Clovis First: a migration of people belonging to the Diuktai culture in Siberia across the Bering Land Bridge sometime between 16,000 and 14,000 years ago, and south of the Ice Wall—probably down an ice-free corridor—after the LGM. This model is based predominantly on an emphasis of the early Alaskan archaeological record, but does not account for pre-Clovis sites or match the genetic record very well. The model favored by a small group of archaeologists on the other end of the spectrum is one in which people came to the Americas very early—some have proposed as early as 130,000 years ago. I (and most archaeologists) do not find this model very convincing, as it has little archaeological support and is completely at odds with what genetics shows us. The third model—one that I think best fits the totality of both the archaeological and genetic data—posits an entry into the Americas sometime after the first traces of people in Siberia at sites such as Yana around 30,000 years ago. Exactly how early one thinks this may have happened differs depending on which pre-Clovis sites are accepted; the majority of scholars agree that people were present in the Americas by at least 14,000 years ago. Some favor 18,000 to 15,000 years ago to account for the majority of pre-Clovis sites and genetic evidence, and still others argue for ...