Birds can’t taste them. Deer avoid them. In fact, humans were thought to be the only animals on Earth that love red, hot chili peppers — that is until a recent study revealed one other animal appears to enjoy them.

Recently, a team of scientists at the Kunming Institute of Zoology in China (which is home to 2,000 tree shrews) were trying to determine what food tree shrews in their lab prefer to eat. They were shocked to learn it was chili peppers. Next, they studied tree shrews in the wild and discovered they ate one particular pepper, the Piper boehmeriaefolium, and actually preferred to eat it over other plants and vegetation.

upclose of tree shrew So far, tree shrews are the only other animals we know of that eats peppers and enjoys them. (Photo: Carlos Amarillo/Shutterstock)

Scientists were trying to figure out exactly why tree shrews enjoyed eating peppers and learned that tree shrews have a mutation in the TRPV1 ion channel protein that lowers their sensitivity to capsaicin, the compounds found in peppers that create a burning sensation in any animal tissue it touches.

While tree shrews seemingly appear to enjoy eating spicy peppers with reckless abandon, how is it that humans evolved a liking for hot spices when the vast majority of the animal kingdom avoids it like the hot plague?

The evolution of eating peppers

In 2010, the New York Times took a look at how this happened, as well as the psychology behind eating hot spices.

Chili peppers began making their way around the human diet as early as 7500 BC. There is archeological evidence that chili were cultivated in South and Central America. Christopher Columbus brought the first chilies to the old world and was the first to call them peppers, as they resembled the white peppers indigenous to Europe. Adding flavor to food at this time was so extravagant that some countries used black peppercorn as a currency. Soon chilies had made their mark on India, Central Asia, Turkey, Hungary and the world.

As the New York Times points out, some experts say we reach for the hot sauce because of its inherent health effects. Chili peppers can lower blood pressure. They are also an excellent source of vitamin C, vitamin B, potassium and iron. Some research shows that the pain of chilies can kill other pain. So when a person eats chili, he is experiencing the same sensation as if his tongue was on fire. Experts think capsaicin may have evolved in plants to protect them against fungi because it is anti-microbial.

But others say these health benefits are not enough to explain why some people love chilies while others don't. Dr. Paul Rozin at the University of Pennsylvania is an expert on human likes and dislikes and author of "How Pleasure Works: The New Science of Why We Like What We Like." As he told the New York Times, "I don’t think they [the health benefits] have anything to do with why people eat and like it.” But Rozin is quick to add, “This is a theory. I don’t know that this is true."

Instead, Rozin says the rate at which people consume chilies has more to do with "benign masochism." His research shows that people rate the level just below unbearable as the most pleasurable amounts of chili they can consume. In places like India and South America, hot peppers are part of the daily cuisine. But in America, there is a capsaicin following that involves T-shirts, clubs, and the hottest hot sauce you can find. Experts say this originates from a primal need to chest thump.

Editor's note: This article has been updated since it was originally published in September 2010.

Man isn't the only animal to find pleasure in the pain of peppers
For years, scientists thought humans were the only animals that enjoyed eating peppers until they studied the tree shrew.