Mushroom-Cloud Spicy: The Link Between Fiery Foods and Fungi

Don't worry, that's not a giant bug on the first tomato of summer. It's a tiny bug on a chile pepper about the size of a caper. But don't let its size fool you: that's one of the hottest peppers out there, the chile piquin, which grows wild in Bolivia.

I remember sampling a few of these chiles at a dinner party in Missoula, Montana, some years ago. Scientists describe the taste as "pungent," which is kind of like calling a bad pinot noir "cheeky" or Henry VIII "irritable." My recollection goes more like this: a whiff of ozone, a grass fire ripping across my tongue, and then the lingering sensation of pavement that has just been peeled out on by a 17-year-old in his parents' car. This week, the host of that party - Joshua Tewksbury, now an assistant professor at the University of Washington - announced a breakthrough in understanding why chiles get so hot.

Turns out it has little to do with punishing the taste buds of mammals; nor science's next best guess, which involved singling out birds to carry the seeds to useful places. Instead, the chemical warfare seems to be directed at a fungus, called Fusarium, that's deadly to chile seeds. Spores get into the chiles through holes made by bugs as they feed. (Look closely, and you can see this bug's straw-like beak plunged between its two front legs and into the chile's skin.) Like good scientists, Tewksbury and his research team went to great lengths to test their idea. They sampled wild chiles across 600 square miles of Bolivia. Chiles with more bug-beak holes contained more the spicy chemical capsaicin - and were infected with fungus less often. To clinch the deal, the researchers built imitation chiles and loaded them with differing amounts of capsaicin.

Like the real thing, hot fakes were much more resistant to fungal infection. So chile plants turn up the heat depending on the risk they face from fungi. Could something similar be at work in the evolution of culinary marvels like the four-star panang curry I had for lunch? Did humans start eating fiery foods, back in the days before refrigeration, as a kind of insurance?