An interesting intersection of plant physiology, ecology and evolution that asks the question: why are some chilies hot and some not? Although we have certainly had some effect with artificial selection there is also a great variation in the heat content of the wild relatives of our domestic chilies.
You can read the paper in PNAS: Evolutionary ecology of pungency in wild chilies. But before you do so you might want to think about how you would generally go about addressing such a topic. What are some possible hypotheses and how would you go about testing them?
The New York Times picked up on this story too.