Family information and history

According to Schroeder, the high prevalence of this gene marker among native populations of North and South America - and its absence in most of Asia - lends strong support to the idea that Native Americans can trace their ancestry to a common founding population. The 9RA mutation probably occurred in an ancestral population located at the eastern edge of Siberia, which subsequently migrated over the Bering land bridge, Schroeder says (watch how the land bridge was gradually submerged as see levels rose). There may have been multiple migrations from this founding population, occurring thousands of years apart, she adds. "How many times did people cross the Bering land bridge? That would be a very difficult question to answer," says Jeffrey Long at the University of Michigan Medical School in Ann Arbor, Michigan, US, who contributed to the new study. Other experts have previously suggested that Native Americans do not share a common ancestry because of the linguistic and dental differences among populations. Journal reference: Biology Letters (DOI: 10.1098/rsbl.2006.0609)