Gibraltar’s famous Barbary macaques have hit upon a clever but dirty solution to the perils of tourist handouts: swallowing soil to settle their stomachs after gorging on chocolate, crisps, ice cream and other junk food. A University of Cambridge study has, for the first time, documented regular “geophagy” – intentional dirt-eating – among the only free-ranging monkey population in Europe. Troops with the closest contact with holidaymakers eat far more soil, with rates spiking during the busy summer season. Researchers believe the high-sugar, high-fat, low-fibre snacks disrupt the monkeys’ gut microbiome and cause digestive misery. Eating dirt appears to act as a natural buffer, lining the gut, supplying minerals and beneficial bacteria, and limiting the absorption of irritating compounds. Dr Sylvain Lemoine, a biological anthropologist at Cambridge, explained: “Foods brought by tourists and eaten by Gibraltar’s macaques are extremely rich in calories, sugar, salt and dairy. This is completely unlike the foods typically consumed by the species, such as herbs, leaves, seeds and the occasional insect.” The behaviour lets the monkeys keep bingeing on calorie-dense …