DNA Sequences Suggest 250 People Made Up Original Native American Founding Population

“It is difficult to go back in time to follow the populations, but we can characterize contemporary genetic diversity and estimate the mutation rates that have occurred in different regions,” Crawford said.

In a 2015 study, Crawford was part of a group that found the ancestors of all present-day Native Americans entered the Americas from Siberia into what is now Alaska no earlier than 23,000 years ago. This founding group did split into the Athabascans and Amerindians after spending no more than an 8,000-year isolation period in Beringia — the land bridge that once connected Siberia to Alaska.

In this new study, the researchers sequenced DNA from the nine independent, non-coding regions of the genomes from indigenous peoples distributed from China to South America spanning over 15,000 years. They determined the breeding size or founding populations by isolation-with-migration computer simulation models based on 100 million generations. Each analysis revealed founding groups were between about 229 to 300 people. This led the group to estimate the parameter for the original founding population of Native Americans of about 250 people.

Recognizing the size of this genetic bottleneck during the populating of the Americas is important for determining the extent of genetic markers needed to characterize Native American populations in genome-wide studies and to evaluate the adaptive potential of genetic variants in this population, according to the research group.

Crawford said the genetic data helps paint a fascinating picture of how the ancient migration unfolded.

“It wasn’t a matter of a group that announced, ‘let’s go follow this one,’” he said. “It was a matter of population fission among hunters and gatherers. There would be about 50 people, and when the population’s fertility gets higher and higher, the population splits into the next so-called ‘county’ and then the next. After 15,000 years, you can put them all the way down in Argentina.”

The project required collaboration from researchers across the Americas, especially to gain access to the DNA samples and cooperation of various Native American populations and those in Siberia and Asia. The study’s corresponding author is Nelson J.R. Fagundes of Universidade Federal do Rio Grande del Sul in Brazil. Co-author Rohina Rubicz of the Division of Public Health Sciences at the Fred Hutchinson Cancer Research Center in Seattle completed her doctoral training at KU. Larissa Tarskaia, originally from Yakutia, Siberia, from the KU Laboratory of Biological Anthropology, served as a post-doctoral researcher under Crawford.

Contacts and sources:
University of Kansas