Have been curious about this for a while, but not curious enough to actually go looking for an answer. Thankfully the power of the internets and the curiosity of Paul Sherman, a professor of neurobiology and behavior at Cornell University have given me a potential answer to this question.
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.
Very sensible answer it has always seemed somewhat counterintuitive that you would eat very spicy foods in already hot countries but apparently there is an evolutionary answer.
"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?