Scientists have long speculated that high diabetes rates among Native Americans may have roots in the evolutionary past. "Thrifty" genes that helped ancient hunter-gatherers store fat for survival during famine may contribute to diabetes in modern times of plenty.
But a new analysis of fossil feces from an Arizona cave suggests that the evolution of thrifty genes had little to do with famine and much more to do with the nature of the ancient feast. The research, reported in the August issue of Current Anthropology, shows that prehistoric hunter-gatherers in the Southwest lived on a diet remarkably high in fiber, low in fat, and consisting largely of foods with extremely low glycemic indices. That diet alone, the researchers say, could have been enough to fix fat-hoarding genes in place.
"What we're saying is we don't really need to look to feast or famine as a basis for thrifty genes," said Karl Reinhard, an archaeologist at the University of Nebraska-Lincoln and one the study's authors.
Native Americans have some of the highest rates of type 2 diabetes of any ethnic group. In some populations, up to half of adults suffer from the disease. The idea that this prevalence might be tied to ancient cycles of feast and famine first emerged in the 1960s and has been debated ever since.
"To understand the basis of these high rates of diabetes, one has to look at the best dietary data one can find," Reinhard said. "That comes from coprolites," the technical term for fossil dung. "By looking at coprolites we're seeing exactly what people ate."
Over the years, Keith Johnson, an archaeologist at California State University, Chico, directed excavations at Antelope Cave. Johnson and other archaeologists have collected nearly 200 coprolites from Antelope Cave, a deep cavern located in northern Arizona, just across the border from St. George, Utah. For as long as 4,000 years, the cave has been host to people from various c
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