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Prehistoric Health

Prehistoric Health
UMaine anthropologist's analysis of biological evidence offers unprecedented clues to the diets and lives of early Americans

About the Photo: "This study is important because it is the first analysis of the DNA from paleofeces that recovers information not only on the diet of the ancient peoples but also DNA of the people themselves. This is the first step in being able to analyze the DNA of ancient people and biological affinity, as well as poetentially obtaining information regarding ancient health and disease." Kristin Sobolik

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On a warm fall morning 2,000 years ago, she left her bed of wild grasses and oak leaves at the back of the rock shelter to prepare a small cooking fire. Breakfast for her children and elderly parent included acorns ground the night before, dried turtle meat and prickly pear fruit.

The men in her clan were hunting in a narrow canyon in the mountains.

If the weather was favorable that year, these nomadic people of what was to become the American Southwest would have had a bounty of yucca fruit, wild grapes, persimmons and greens. Fish, squirrels, antelope, deer, birds and lizards would have been some of the sources of meat. However, in dry years, food would have been scarce, and the clan might have had to stay on the move.

A sequence of dry years could have meant starvation or, at least, increasing competition with other clans for food and water.

Clues about these ancient American societies and the environmental changes they endured have come from a variety of sources. Rock art, stone tools, skeletons and midden heaps have been used by archaeologists to describe social organization and living conditions that go back 10,000 years or more.

What about the children?

During a sabbatical at Grinnell College, Iowa, in 2000, University of Maine Associate Professor of Anthropology and Quaternary Studies Kristin Sobolik completed the first comprehensive analysis of what southwestern archaeological studies reveal about children's health. Her analysis could provide the basis for a re-evaluation of theories about the nutritional adequacy of ancient American diets.

Sobolik analyzed studies that covered about 1,500 years, starting in the first century A.D. In particular, she focused on the condition and ages of skeletal remains.

Sobolik found that the average infant mortality rate was nearly 50 percent at the beginning of the period, declining to around 35 percent at the end. Health tended to be better in large settlements than in small ones.

Both of these results are contrary to conventional archaeological wisdom. Early agricultural development is usually associated with a decline in human health. In large settlements, health is thought to have been worse because of parasites associated with livestock, stored foods and accumulations of human waste.

Kristin Sobolik of The University of Maine Department of Anthropology and Institute for Quaternary and Climate Studies is part of a scientific team that has advanced another source of evidence: DNA from ancient human feces, or coprolites.

She is contributing to our understanding of the past.

"In the soil pits that we dig, coprolites stand out because of their shape. They also tend to be distinct from soil particles," Sobolik says. "Once we get them back to the lab, we also run tests that distinguish them from the scat of other animals."

Scientists have long used the presence of undigested seeds, hair and other clues in coprolites to determine what people ate. The power of DNA analysis allows scientists to expand their search to include other foods, especially those that might have been more completely digested.

The author of several publications on the health, diet and nutrition of prehistoric Americans, Sobolik specializes in the analysis of biological evidence at archaeological sites. She has worked in both the Southwest and the Northeast since she received her Ph.D. at Texas A&M in 1991.

Sobolik can sift through layers of soil and often complex mixtures of animal and plant remains to distinguish clues that are relevant to human activity from those that simply reflect the presence of wildlife. In describing evidence that is uniquely human, she says, scientists must be careful to set aside items left by rodents, owls, mountain lions and other animals.

Archaeologists working in the Southwest have an advantage over their colleagues elsewhere, says Sobolik. Extremely dry conditions promote the preservation of bones and other remains. By contrast, Maine's acid soils and relatively high humidity cause materials to decompose rapidly.

Last year, in an article in the Proceedings of the National Academy of Sciences, Sobolik and her colleagues published the first paper describing the results of DNA analyses of human fecal samples. The three coprolites came from four to five feet below the ground in Hinds Cave, a rock shelter in southwest Texas. Carbon dating showed them to be more than 2,000 years old.

The data indicate a surprisingly rich diet composed of a variety of plants and animals, including acorns, yucca, bighorn sheep, pronghorn antelope and cottontail rabbit.

"This study is important because it is the first analysis of the DNA from paleofeces that recovers information not only on the diet of the ancient peoples but also DNA of the people themselves," says Sobolik.

"This is the first step in being able to analyze the DNA of ancient people and biological affinity, as well as potentially obtaining information regarding ancient health and disease."

In a separate study published in 1995, Sobolik and another team of scientists analyzed hormones in coprolites to see if males could be distinguished from females. Based on work in Mammoth and Salt caves in Kentucky, Sobolik's initial study showed that the analysis could be done. All the coprolites at the sites were from men.

It is important to understand how ancient societies were organized and how subgroups behaved, Sobolik says. That includes differences between the genders.

"Archaeologists often talk about how the population did this or that, but we know that there are subgroups of men and women, as well as children," says Sobolik.

by Nick Houtman
April-May, 2002

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