Sunday, May 17, 2009

Old and Fat


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From Slate magazine

Were there obese people 35,000 years ago?
By Christopher Beam
Posted Friday, May 15, 2009, at 6:46 PM ET

Researchers say a "Venus" figurine discovered in 2008 in southern Germany and created an estimated 35,000 years ago may be the oldest statue ever found. Its sexually suggestive figure— large breasts, large rear end—is said to connote fertility. But it also looks extremely fat. Were there obese people in prehistoric times?

Few, if any. Obesity is defined as having a body mass index higher than 30—the equivalent of being about 5-foot-11 and 220 pounds. The best indicator of body type among prehistoric peoples is present-day societies with a similar lifestyle—that is, hunter-gatherers. From the San people of Botswana to the Pygmies in central Africa to the Batek of Malaysia, groups that fall into this category tend to be small and extremely thin. The Baka of Cameroon, for example, are about 5 feet tall and weigh around 105 pounds, giving them an average BMI of 20. Hunter-gatherers are usually thin because they subsist largely on fruits and vegetables, underground tubers, and, in some regions of Africa, honey. They also get calories from animal meat, and some of their diets are especially fish-heavy. But many tribes insist on distributing the meat evenly among the group, so there's rarely enough for one person to get fat on. Hunter-gatherer tribes also stay thin, unsurprisingly, due to a generally active way of life.

Fossils are of little use in determining the relative fitness of Stone Age humans because, for the most part, the bones of a 150-pound man look similar to the bones of a 250-pound man of the same height. Many old bones do have stress fractures or signs of arthritis, but it's hard to conclude that these indications of degradation are due to obesity. Neanderthals 200,000 years ago were shorter and stockier than we are now, but, again, there's no evidence that they were obese.

Obesity likely began with the advent of agriculture 12,000 years ago. Food surpluses and the relatively sedentary lifestyle on settlements made overconsumption possible for the first time in human history. Another factor was the rise of processed foods and, with the invention of the steel roller mill in the late 19th century, the possibility of mass-marketing those foods. Grains and other carbohydrates that have been broken down are easier to digest. As a result, you get hungry again faster. Some scientists also theorize that people weighed less in earlier eras because they were exposed to more infections. (If you're eating carrots out of the ground—as opposed to a sealed plastic bag—you're likely to have constant minor parasitic infections.) When you're fighting an infection, your body temperature rises, and you burn more calories.

Some women in hunter-gathering societies do have abnormally large buttocks, a condition called steatopygia. It's especially common among the Khoisan in southern Africa and tribes in the Andaman Islands. It is sometimes considered a sign of beauty, and may have inspired some of the more voluptuous ancient figurines. The most famous example of steatopygia was the Hottentot Venus, a Khoikhoi woman whose physical characteristics made her a sideshow sensation in 19th-century Europe.

Got a question about today's news? Ask the Explainer.

Explainer thanks Nathaniel Dominy of the University of California Santa Cruz and Jeff Leach of Paleobiotics Lab.

Christopher Beam is a Slate political reporter.
Photograph by H. Jensen © copyright Universität Tübingen.
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