Ancient math refines theories of...( Evolutionary biologists are used to d...)

Evolutionary biologists are used to digging into the past--but rarely in a quest to unearth equations. One group of scientists, however, has dusted off a 200-year-old formula to help reconcile discrepancies that crop up among DNA studies designed to sort out how species are related to one another. In the June 30 issue of Science, John Huelsenbeck, assistant professor of biology at the University of Rochester and his colleagues show how 18th century math can help biologists grapple with the flood of DNA sequences coming from genome sequencing projects. His colleagues are Bruce Rannala, assistant professor of medical genetics at the University of Alberta, and graduate student John Masly of the University of Rochester.

"This method is a revolutionary approach to addressing questions concerning the evolution of important traits," says Paul Lewis, professor of ecology and evolutionary biology at the University of Connecticut and an expert at inferring evolutionary trees from DNA sequences. "This means that determining an evolutionary tree will be less biased by one particular estimate. The investigators of this study continue to be pioneers in this field."

The mathematician to whom Huelsenbeck, Rannala, and Masly have turned is Thomas Bayes, a British Presbyterian minister who devised a formula to account for uncertainties in data--uncertainties such as when one method suggests chimps are more like humans than orangutans, while another says the exact opposite. Bayes' formula allows informed guesses to be combined with new data. As the scientist collects more data, the initial guess carries less weight, and so the most accurate answer, such as which evolutionary family tree correctly depicts how birds split from reptiles, gradually takes shape. Currently, scientists are forced to treat evolutionary trees as ironclad truth, even though the results from different studies often disagree with one another. Bayesian mathematics accommodates uncertainty about the evo
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Contact: Jonathan Sherwood
jsherwood@admin.rochester.edu
716-273-4726
University of Rochester
28-Jun-2000