The Global Spread of the Chilli

A Few flavours have travelled so far from home as the heat of the chilli. Today chillies are central to the cooking of India, Thailand, China, Mexico, Hungary and much of the rest of the world, yet the plant is a native of the Americas alone. Archaeologists believe that peoples in Mexico and further south had already been growing and eating chillies for thousands of years before any European set eyes on one, making it among the oldest cultivated crops of the New World. Wild chillies still grow across Central and South America, small and fiercely hot, and it was from these that farmers, over countless generations, coaxed the enormous variety of shapes, sizes and strengths that fill the world's markets today.

B The famous heat comes from a single family of chemicals, chiefly one called capsaicin. Capsaicin does no real harm to the flesh of the mouth; instead it plays a trick on the nervous system. It binds to the very receptors that normally warn the body of dangerous heat, so that the brain is fooled into feeling a fierce burning even though nothing is actually being burned. This is why a mouthful of chilli feels hot in much the way a scalding drink does, and why a gulp of cold water does so little to help. The chemical dissolves in fat and oil but not in water, which is why a mouthful of milk or a spoonful of yoghurt soothes the burn far better than a glass of water ever could, a piece of practical knowledge long built into the cooking of chilli-loving cultures.

C Why should a plant go to the trouble of making such a chemical? The answer appears to be a clever piece of self-defence. The receptors that capsaicin inflames are found in mammals, whose grinding teeth would destroy a chilli's seeds, but birds do not react to capsaicin at all. Birds can therefore eat the fruit freely and carry the seeds, still able to sprout, to new ground. In effect the chilli punishes the animals that would waste its seeds while rewarding those that spread them. The arrangement is beautifully precise: the seeds pass through a bird unharmed and are dropped, together with a little natural fertiliser, far from the parent plant, so that the chilli's fire is not a weapon against all comers but a carefully aimed instruction about which animals may, and may not, eat its fruit.

D The plant's confinement to the Americas ended suddenly with the voyages of Columbus at the close of the fifteenth century. Portuguese and Spanish ships carried chillies along their trade routes, and within roughly a hundred years the plant had taken root across Africa and Asia, transforming cuisines that had never known it. So thoroughly did the chilli conquer these kitchens that many people still assume it must be native to India or Thailand rather than a newcomer from across the sea. In some places the chilli was taken up so eagerly that it reshaped entire national cuisines within a few generations, and it is now hard to picture the food of Sichuan, Bengal or Hungary without it, even though none of these places had so much as tasted the plant before the sixteenth century.

E Because some chillies are mild and others ferocious, a way of measuring their strength was eventually needed. In 1912 a pharmacist named Wilbur Scoville devised the scale that still bears his name, ranking chillies by how much they must be diluted before the heat can no longer be tasted. Sweet peppers sit at the bottom with a score of zero, while the fiercest cultivated varieties reach into the millions of Scoville units. Modern laboratories can now measure the exact amount of capsaicin in a chilli far more precisely than Scoville's original taste tests ever could, but his scale, and the vivid idea behind it, have stuck, and growers still compete fiercely to breed the hottest pepper in the world.

F Given that capsaicin causes what the body reads as pain, the human love of chillies is something of a puzzle. Part of the answer is that the burn prompts the brain to release endorphins, the body's own painkillers, producing a mild natural high that many people find pleasurable. A taste for chilli must usually be learned, often in childhood, but once acquired it can become a genuine craving, a rare case of humans deliberately seeking out a sensation that nature designed to drive them away. Some researchers suspect that part of the appeal is the thrill of a danger that is not truly dangerous, the same safe flirtation with fear that draws people to frightening films or fast rides, with the mouth, rather than the mind, doing the trembling.