Evolution & Disease

Evolution & Disease

Towards the end of On the Origin of Species, Charles Darwin wrote, “Endless forms most beautiful and most wonderful have been, and are being, evolved.” Although Darwin was thinking of forms like finch beaks and whale hips, scientists today are studying evolutionary change at the genetic level, searching for markers and mutations on the human genome that may yield insights into disease prevention and treatment.

Noah Rosenberg, an assistant professor of biostatistics who also holds appointments in the Department of Human Genetics, the Department of Ecology and Evolutionary Biology, the Bioinformatics Program, and the Life Sciences Institute, puts it this way: “We’re trying to understand how disease frequencies vary across populations, how that’s a result of human evolutionary history, and how we can use that history to help identify disease mutations.”

In a process that would have been nearly impossible even a decade ago and unimaginable in Darwin’s time, Rosenberg and his colleagues are using a combination of mathematical modeling, computer simulations, and statistical inference to sift through nearly 3,000 markers in the genotypes of over 900 unrelated individuals in 50 populations from around the world.

Rosenberg and his team are looking at patterns of genetic variation, with the aim of determining the extent to which these patterns reflect those seen in the HapMap Project, a $100-million international effort to catalog four million markers in the human genomes of four populations: Yoruba, European-American, Han Chinese, and Japanese.

To date, the researchers have found an 83% overlap between genetic variants in both the HapMap and the broader pop-ulation, which suggests that the HapMap populations can be used to predict genetic variation in populations that have not been studied on such a massive scale. As a result, panels of markers chosen optimally for mapping disease genes in the HapMap populations will also be effective for mapping these genes in the broader population. Given that it would be prohibitively expensive to extend the HapMap project to all human populations, “this is good news for the design of mapping studies,” says Rosenberg.

Rosenberg hopes to extrapolate information from his research about the frequency of disease mutations across human populations, and ultimately to understand why genetic diseases seem to vary in frequency from one population to the next.

A single human genotype, Rosenberg notes, is the result of a complex genealogical history. But increasingly that history is providing valuable clues to human health and confirming what Darwin envisioned when he wrote in his Origin of Species that light would someday be “thrown on the origin of man.”

Photo by Martin Vloet, UM News Photo Services

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