Gran Dolina boy Illustration by Mauricio Antón

Around 800,000 years ago, a group of early humans took shelter in a cave at the site now called Gran Dolina. Researchers have unearthed an intriguing collection of hominid fossils buried inside the filled-in cave that are unlike any other fossils found in Africa, Asia or Europe. As a result, these hominids have been classified as a new species, Homo antecessor, from the Latin word for explorer. Homo antecessor may have been the first hominid to populate western Europe.

Only about 90 fragmentary fossils have been found to date at Gran Dolina, so not much is known about these first Europeans. But the evidence does reveal one surprising detail. The Gran Dolina hominids not only butchered animals in the shelter of their cave—they butchered other ancient humans as well, making them the first known cannibals.