Researchers have hypothesized that migrations into higher, colder latitudes may lead to the evolution of fast-burning metabolisms that keep cells warm in chilly conditions, boosting cold tolerance. In Developmental Cell, on April 10, researchers show that a gene called THADA, which has previously been identified as one of the key genes in humans that differs in people from arctic latitudes and people from tropical latitudes, helps flies burn energy from fat. When the gene is knocked out in flies, they become obese and burn less energy. This finding may be a clue to previously observed correlations between ancestral latitudes and metabolism in humans.