Iñigo Mujika

Baboon. (Photo: Dick Mudde)

Robert M. Sapolsky is Professor of Biology and Neuroscience at Stanford University. For over a decade, he has been spending his summers in the Masai Mara National Reserve in the Serengeti Plain of Kenia, studying the relationships between social behavior and dominance rank in wild baboons, the amount of social stress they experience, and how their bodies react to stress.

According to Robert Sapolsky, “an average baboon in the Serengeti spends 30 to 40 percent of each day foraging – climbing trees to reach fruit and leaves, digging laboriously in the ground to unearth tubers, walking five or ten miles to reach sources of food. Their diet is spartan: figs and olives, grass and sedge parts, corms, tubers and seedpods. It’s unusual for them to hunt or scavenge, and meat accounts for less than 1 percent of the food they consume. So the typical baboon diet teems with fiber and is very low in fat, sugar, and cholesterol.”

A few years ago, a garbage pit was digged in the middle of the territory of one of the baboon troops studied by Sapolsky, where the garbage produced by tourists was dumped. Food left overs at the garbage dump included fried drumsticks, beef, fruit salad, fragments of pies and cakes, custard pudding… “processed sugars, fat, red meat, and cholesterol, our modern Four Horsemen of the Apocalypse” as described by Sapolsky himself.

The group of baboons moved to the trees surrouding the dump, and their typical activity pattern changed in such a way that they would only get active at the time of arrival of the garbage tractor. Of course, their usual diet was completely modified as they were now on a “Westernized” diet.

An “average wild baboon eating a natural diet had cholesterol levels that would shame the most ectomorphic triathlete” and more than half the total cholesterol is in the form of high- density lipoproteins, i.e. the “good” cholesterol. But when Sapolsky studied the Garbage Dump baboons, a different picture emerged. “Cholesterol levels were nearly a third higher, and most of the increase was attributable to a rise in damaging low-density lipoproteins, the type that builds up plaque on artery walls.” But not only that, “levels of insulin were more than twice as high in the Garbage Dumpers as in those eating a natural diet. This hormone is secretedby the pancreas in response to eating, especially eating rich, sugary food, and its function is to tell cells to store glucose for future as energy. If insulin levels rise too high, however, cells become inured to its message; instead of being stored, glucose is left circulating in the bloodstream.

It’s this state of affairs that can eventually lead to adult-onset diabetes, a distinctly Western malady. Since the Garbage Dumpers came from gene stocks similar to those of the natural foragers, genetic differences couldn’t account for their much higher insulin levels. The most likely suspect was their junk food diet and their relative inactivity.”

Reference

Sapolsky, RM. The trouble with testosterone: and other essays on the biology of the human predicament. Touchstone: New York, 1997.