Question: Why are chili peppers hot?
Answer: To protect them from mammals, according to zoologist Josh Tewsbury and ethnobotanist Gary Nabhan from Northern Arizona University. Most mammals--other than humans--avoid the peppers because of sensitivity to capsaicin, the chemical that gives peppers their spice. But birds are unaffected by the chemical and eat peppers happily, the team reports in the July 26 Nature. That's crucial because birds release the seeds in their droppings, ready to germinate. If mammals ate the seeds, however, they would crunch them or otherwise render them infertile.