Scientists Trace Tooth Decay Bacterium through Time

Streptoccocus mutans, the bacterium associated with tooth decay, has evolved along with its human hosts in a clear line that can be traced back to a single common ancestor who lived in Africa between 100,000 and 200,000 years ago, investigators from the New York University College of Dentistry report.

"As humans migrated around the world and evolved into the different races and ethnicities we know today, this oral bacterium evolved with them in a simultaneous process called coevolution," said Dr. Page Caufield, professor of cariology and comprehensive care at the NYU dental school and leader of the research team.

The NYU team used the same DNA "fingerprints" and other biomarkers to track the evolution of S. mutans as scientists have previously used to trace human evolution back to a single common African ancestor, known as "ancestral Eve."

They gathered more than 600 samples of the bacterium, eventually focusing on about 60 strains collected from Chinese and Japanese; Africans; African-Americans and Hispanics in the United States; Caucasians in the United States, Sweden, and Australia; and Amazon Indians in Brazil and Guyana.

"It is relatively easy to trace the evolution of S. mutans, since it reproduces through simple cell division," said Dr. Caufield. "By tracing the DNA lineages of these strains we have constructed an evolutionary family tree with its roots in Africa and its main branch extending to Asia. A second branch, extending from Asia back to Europe, traces the migration of a small group of Asians who founded at least one group of modern-day Caucasians."

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