Bacterium helps trace migration of humans

Medicine & Science

March 17, 2003|By Michael Stroh | Michael Stroh,SUN STAFF

Scientists unraveling the story of mankind's ancient migrations have enlisted the help of an unlikely historian: an ulcer-causing bacterium that lives in the gut.

An international research team reports in Science that the S-shaped bacterium Helicobacter pylori, best known for its miserable role in peptic ulcers and stomach cancer, may also harbor clues to human whereabouts over the centuries.

Half the population of the planet may be infected with the bug, which is thought to be passed by contact from mother to child during infancy.

Because H. pylori spreads tummy to tummy from one generation to the next, scientists have found that Asian, European and African stomachs can harbor distinct strains. So, theoretically a scientist could trace a person's origins through his stomach.

Mark Achtman of the Max Planck Institute for Infection Biology in Berlin and colleagues collected 370 stomach samples from more than two dozen geographic and ethnic groups. By analyzing genetic codes, the scientists divided the microbes into four major categories - two from Africa and one each from Europe and East Asia.

Most of the findings confirmed migration patterns scientists had already suspected. European stomachs contained a jumble of H. pylori genes, showing them to be a mosaic of several populations.

The East Asian strain turned up among the Maori of New Zealand and in Native Americans - lending further support to the theory that Asians made their way to North America across a land bridge that once linked the continents.

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