This is Part 1 of the series Food for Thought (And for Eating), about science in the kitchen
Check out the recipe for chiles rellenos that accompanies this post.
Everyone knows that chile peppers can be hot. Some are almost inedible. But why do they taste hot? The answer: chile peppers wage chemical warfare on your mouth. Specifically, they contain a chemical called capsaicin, which is responsible for their ‘heat’.
Capsaicin binds to the same pain receptors that send emergency signals to your brain when you take a swig of scalding hot coffee. So when you take a bite of five-alarm chili your brain thinks that you’re actually burning the inside of your mouth. And, as I recently discovered while cutting up habanero peppers, capsaicin can also make your brain think that you’ve lit your fingers on fire. But the effect eventually wears off, and there aren’t any long-term consequences.
In short, capsaicin is an irritant, which is why the ability to produce it evolved in chiles in the first place. In the wild, mammals don’t eat chiles because, apparently, they don’t like the burning sensation caused by capsaicin. Birds, on the other hand, don’t have the same pain sensory pathway as mammals, so they’re immune to capsaicin’s irritating effects, and they eat wild chiles all the time. But why do chile plants want to encourage birds to eat their peppers? And what do they have against mammals? The answer has to do with the chile’s seeds. While mammals tend to chew up the seeds along with the pepper, birds swallow the seeds whole, allowing them to pass through their digestive system none the worse for wear. This means that birds help chiles reproduce by spreading their seeds, while mammals often destroy the seeds. Over thousands of years this situation led to evolutionary adaptations that allowed chiles to produce capsaicin.
But this evolutionary strategy backfired when humans showed up. For whatever reason we humans can’t get enough of the hot, spicy flavor of chiles. Archaeological and genetic evidence suggest that wild chiles originated in Bolivia and gradually spread to their present range extending from the southern border of the United States in the north to the Caribbean in the east and the Amazon and the Andes in the south. Beginning about 6000 years ago chiles were one of the first crops that humans domesticated in the Americas, alongside corn and squash. When Europeans showed up in the Americas 5500 years later, they quickly developed a taste for chiles as well. They began to incorporate chiles into European recipes as a substitute for expensive black pepper, which was imported from Asia at the time.
Since then chiles have spread around the globe and have been embraced by nearly every culinary tradition in the world. But chiles are supposed to be irritating. So why do we love them so much? Other animals certainly don’t like them. Researchers have tried to develop a preference for chiles in rats by slowly introducing pepper flavoring into their food. But the rats continued to choose non-spiced food over chile-containing food when given the option.
An extensive 1980 study of chile preference in humans found that most young children don’t like chiles either – chile-lovers acquire the preference during childhood. The same study proposed that many people like eating chiles for the same reason they enjoy roller coasters or taking a very hot bath. These experiences are identified as “controlled risks” – they may trigger a negative physiological response but we know they are ultimately harmless. They offer a thrill. Even so, most people interviewed for the study claimed they liked chiles for their flavor or flavor-enhancing capability.
- Read about another evolutionary advantage of capsaicin: its anti-fungal properties, on the blog, Not Exactly Rocket Science
- Check out Harold McGee’s blog, Curious Cook, for a great series of articles on chiles and science
- A short post on chile science from the blog, The Frontal Cortex
- Read about capsaicin as an evolutionary strategy to deter mammals (PDF)
- Read about the archaeology of chile domestication in Science (PDF)
- Read about the development of chile preference in humans (PDF)