for National Geographic News
People who live in warm climates are attracted to spicy foods because the red-hot seasonings keep people healthy, according to a scientist who takes a Darwinian approach to medicine.
"The Darwinian approach asks the question, Why are certain things the way they are, which is a complement to the approach of asking, How do things work?" said Paul Sherman, a professor of neurobiology and behavior at Cornell University in Ithaca, New York.
Sherman's research shows that people in warmer regions of the world benefit from eating spicier foods, because spices are natural antimicrobials. Food-borne pathogens and parasites are more prolific in warmer climates, and spices can kill or inhibit their growth.
When people in a country like Thailand, for instance, eat a spicy meal, they are much less likely to spend the next day with a bout of diarrhea than people in that region who eat bland foods.
"Humans do what makes them feel good, and they learn from each other," Sherman said, adding that people in hot climates learned that spicy food is less likely to make them sick and thus developed a preference for it.
"The simple mechanism is they felt better after eating food that was spicy, and since they felt better they learned to like that stuff," Sherman said. "Over time, word-of-mouth spread the news."
In cooler climates such as Iceland, a steak left outside overnight might freeze. The cold would slow germ growth in the meat, rendering the use of spices unnecessary. As a result, Icelandic dishes tend to be bland.
But that's not a bad thing, Sherman said. Why take antimicrobials when they are not needed?
Randolph Nesse is the director of the Human Evolution and Adaptation Program at the University of Michigan in Ann Arbor. He said Sherman's research is a fine example of how behavioral traits are shaped by both natural and cultural selection.
To prove his hypothesis about the climate-dependent evolution of spicy foods, Sherman and his colleagues compared recipes for more than 4,000 meat dishes and 1,000 vegetarian dishes among 36 countries.
As predicted, countries with the warmest climate have the spiciest food. Meat dishes in particular are always the spiciest because a piece of meat lacks defenses against pathogens and parasites. Plants by contrast are where the antimicrobials originate.
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