Paleo-Indian Poop Yields Clues to the Real Ancient American Diet

Native Americans suffer the highest rates of diabetes in the United States -- 16 percent, more than twice the average among Anglos. 

For decades, scientists have thought this modern health crisis may have evolutionary origins, stemming from ancient feast-and-famine cycles that encouraged the selection of so-called "thrifty genes" and people to pile on fat faster in times of plenty, so as to prepare for leaner times to come.

But a recent study of paleo-Indian feces suggests that the health problems modern Natives face may have less to do with scarcity and more to do with the kinds of foods ancient Americans ate.

Karl Reinhard, an archaeologist at the University of Nebraska, led research into human coprolites -- naturally preserved feces -- found at Antelope Cave, Arizona, a sandstone dwelling near the Arizona-Nevada-Utah border. Mammal bones show the cave to have been a popular spot for hunting and butchering jackrabbits, particularly among the so-called Virgin Anasazi, who inhabited the region 1,000 to 1,300 years ago.

Jackrabbit forepaw found in Antelope Cave, Arizona (Credit: Jacob Fisher, California State University Sacramento)

The study found that the paleo-Indian diet was surprisingly high in fiber and low in fat. The historic Southwestern diet is thought to have relied heavily on corn, beans, and squash, but the scat showed -- in addition to corn and hare meat -- heavy traces of sunflower seeds, prickly pear, grasses, and amaranth, also known as pigweed.

In addition to being "very, very high in fiber," the researchers say in a release, these foods are notable for having extremely low glycemic indices, meaning they're slow to raise blood sugar. The index for prickly pear, in particular, they say, "is the lowest recorded for southwestern plant food, and one of the lowest values for any recorded human food."

All of this suggests that prehistoric nutrition was so intensely lean that it, rather than boom-and-bust cycles of rain and drought, may have been the evolutionary pressure that favored those "thrifty genes" in ancient Americans.

None of this provides us with new tools to fight obesity and diabetes among Native Americans, of course. But it does underscore how radically the American diet has changed, and that abundance isn't the same as health.

The research appears in the journal Current Anthropology.