The Original American Colonization

There is no puzzle in American archaeology more resistant to resolution than the original colonization of the American continents. When did the ancestors of the American Indian arrive in the Americas and from what regions of the world did they come? Since at least Thomas Jefferson’s day, researchers have attempted to come to consensus by comparing skeletal remains, language families, cultural elements and archaeological site data; and in the last twenty years, DNA sequencing, including both mitochondrial and Y-chromosome studies. In a paper published in the June 2005 issue of the open access journal Public Library of Science Biology (PLoS Biology), Jody Hey, a geneticist at Rutgers University, introduces a model comparing several DNA loci to apply to this problem. Hey’s model can produce estimates of founding population size, changes in population size, time of population arrival and gene flow. Results of the preliminary run of the model using available data suggest an effective founder population of between 70 and 80 individuals arriving in the Americas between 7,000-14,000 years before the present.

Based on archaeological research, scientists are largely agreed that the Native American populations of today began migrating to the American continents at least 14,000 years ago. There is dissension concerning the number of migration waves, the progress of those migrations, and the originating location of those migrations; as well as whether they began only 14,000 years ago or much earlier. Although it seems unlikely at first glance, previously published estimates on founder populations have ranged between 50 and 10,000; Hey’s model, which balances several strands of DNA data, confirms Steele, Adams and Sluckin’s (1998) demographic models indicating a fairly small number can account for both Paleoindian distributions and population density at the time of Columbus's landing.

DNA studies have been conducted before; Hey’s model balances genetic variable data from the published literature on nine Asian and New World populations. Data used are restricted to previously published DNA chains from Amerind speakers (excluding Na Dene and Eskimo-Aleut speakers) and Asian ethnic chains from China, Mongolia, Korea and Siberia. The results of the effective founder population (those likely to contribute genes to the next generation) indicated a range of 70 to 80 individuals, from an estimated total Asian population of 9,000. The model produced a probable date of entry with the highest probability peaking between 6,000 and 8,000 years ago. In contrast, widely accepted archaeological investigations report dates to 14,000; Hey’s model does include a range between 6,000 and 14,000 within 95% probability.

Hey's findings are important for several reasons, but primarily because they confirm previous research and so provide a useful model for future research, should DNA studies become available for other places and other peoples in the world.

---

References:

Hey, Jody. 2005. On the number of New World founders: A population genetic portrait of the peopling of the Americas. Public Library of Science: Biology 3(6).

Steele, James, Jonathan Adams and Tim Sluckin. 1998. Modelling Paleoindian dispersals. World Archaeology 30(2:286-305.

Thanks to Joseph Powell (University of New Mexico) for his assistance with this report; any errors are mine.