N. America’s 1st Migrants Were Few, Study Says
The founding fathers of North America numbered as few as 70 intrepid Ice Age nomads who first migrated from Siberia, according to a new genetic analysis made public Monday.
Population geneticist Jody Hey at Rutgers University in New Jersey calculated that the first wave of American immigrants was a trickle -- perhaps a single small tribe that struck out on its own from an ancestral population in Asia numbering no more than 9,000 people.
“A tiny fraction went to the New World,” Hey said.
The study of the founding human population of North America -- the most comprehensive to date -- was published Monday in PLoS Biology, an online journal of the Public Library of Science.
“The small number is surprising to me,” said anthropologist Joanna L. Mountain of Stanford University. “We may be looking at the winners here. It is quite likely that other groups came over and did not survive.”
If the original settlers were so few, “that would be quite striking,” said Theodore G. Schurr at the University of Pennsylvania’s Laboratory of Molecular Anthropology. “It would have a lot of biological and medical implications.”
Long frustrated by the paucity of direct archeological evidence, researchers in recent years have searched for any biochemical traces of the early pathfinders that may still survive in the cells of their descendants hundreds of generations later.
Using the tools of molecular biology and population genetics, experts have learned to reconstruct ancient migrations by tracking the movements of telltale genes in geographic patterns. They also can estimate the timing of population movements by calculating the steady mutation rate of key genes.
With a set of computer simulations, Hey calculated the pattern of inheritance of nine genes among contemporary Asian and Native American peoples.
“Every individual gene has its own history,” Hey said. “If you use only one, then you have a good chance of being quite wrong about the history of the population.”
By Hey’s calculations, the wanderers reached North America between 7,000 and 14,000 years ago, more recently than the 15,000 years suggested by archeological evidence, several experts said.
Hey focused on one of the three major language groups in North America -- the Amerind speakers -- who are believed to represent the earliest people who ventured across an ancient land bridge from Siberia into Alaska and then deep into the continent.
The number of these first immigrants whose genes have survived into the present was about 70, Hey said. Counting all adults, however, including those who did not survive long enough to start families, “we might be talking as many as a couple of hundred individuals.”
“It is clear that Native Americans don’t have as much genetic variation as Asians,” Hey said. “There was definitely a bottleneck of some sort.”
