New research suggests that Africans have more sensitive palettes than Europeans and Asians – at least for bitter tastes

A survey of numerous African populations in Kenya and Cameroon found a striking amount of diversity in a gene responsible for sensing bitter tastes. "If they have more genetic diversity, there's more variation in their ability to taste," says Sarah Tishkoff, a geneticist at the University of Pennsylvania in Philadelphia, who presented the findings at a recent conference. Europeans and Asians typically have only one of two forms of a gene called TAS2R38, which detects a bitter-tasting compound called PTC and similar chemicals in vegetables such as broccoli and Brussels sprouts. The gene makes the difference between people tasting a weak dilution of the compound or not, with little nuance in between. To see how Africans stack up, Tishkoff and colleague Michael Campbell offered a wide range of dilutions of PTC to different populations of pastoralists and hunter-gatherers in Kenya and Cameroon. "They keep tasting it until they make a yucky face and spit it out," she says. As a whole, Kenyans and Cameroonians sensed subtler gradients in the concentration than Europeans, they found. The Africans' TAS2R38 genes also contained far more variation than is found in the rest of the world. This could be because heterogeneity offered an evolutionary benefit to populations of Africans at some point in history. "Maybe it was because there were certain plants that were beneficial to eat, but they were also bitter," Tishkoff says. A greater sensitivity to bitter compounds may have helped in detecting the best plants. However, the compounds that cause bitter tastes can be thyroid-damaging, notes Paul Breslin, a neuroscientist at Monell Chemical Senses Center in Philadelphia. If you have a healthy thyroid you want to eat these things because they're packed with vitamins, he says. A diet high in iodine – common in coastal-dwelling people – protects against such thyroid damage, but, iodine intake typically drops off the further people live from the ocean. So bitter-sensitive genes could help these people avoid toxic veggies, Breslin speculates. Tishkoff wonders why, then, Europeans lost some the ability to sense bitterness. Different diets and evolutionary forces offer one explanation, she says. Their lack of bitter taste diversity could also be due to a paucity of genetic variation in the small number of African migrants that became ancestors to the Europeans. In general, sub-Saharan Africans boast more genetic diversity than people native to Europe and other continents. Avoiding potentially toxic plants might not be the only reason for diversity in bitter taste genes, says Theodore Schurr, an anthropologist at the University of Pennsylvania, who was not involved in the study. His team found lots of variation in bitter taste genes in a Siberian population that has historically eaten few vegetables. "We're surprised at the amount of diversity we see there," he says. "We're trying to figure out what this means."