(FILES) This file photo taken on July 23, 2016 shows a chimpanzee fed with frozen food to beat the summer heat at the Bioparc zoo in Valencia. Cooperation is often hailed as a key trait that separates humans from animals, but researchers said August 22, 2016 that our closest relative, the chimpanzee, can learn to work as a team. In fact, chimps prefer cooperation by a ratio of five to one over competition, and find ways to discourage peers from freeloading, said the study in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal. / AFP PHOTO / JOSE JORDANJOSE JORDAN/AFP/Getty Images
