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The researchers created a "family tree" that traces the different mitochondrial DNA lineages found in today's Native Americans. By noting mutations in each branch and applying a formula for how often such mutations arise, they calculated how old each branch was. That piece of information revealed when each branch arose in a single woman. The six "founding mothers" apparently did not live in Asia -- the DNA signatures they left behind aren't found there, Perego said. They probably lived in Beringia, the now-submerged land bridge that stretched to North America, he said. Connie Mulligan of the University of Florida, an anthropologist who studies the colonization of the Americas but didn't participate in the new work, said it's not surprising to trace the mitochondrial DNA to six women. "It's an OK number to start with right now," but further work may change it slightly, she said. That finding doesn't answer the bigger questions of where those women lived, or of how many people left Beringia to colonize the Americas, she said Thursday. The estimate for when the women lived is open to question because it's not clear whether the researchers properly accounted for differing mutation rates in mitochondrial DNA, she said. Further work could change the estimate, "possibly dramatically," she said. Related Links: |
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