In the early Pleistocene, 1.5–1 mya, in Africa, Asia, and Europe, presumably, some populations of "Homo habilis" evolved larger brains and made more elaborate stone tools; these differences and others are sufficient for anthropologists to classify them as a new species, "H. erectus". In addition "H. erectus" was the first human ancestor to walk truly upright. This was made possible by the evolution of locking knees and a different location of the foramen magnum (the hole in the skull where the spine enters). They may have used fire to cook their meat.