900 kya (900 thousand years ago).
A common way of demeaning another group is to call them cannibals. Roman pagans sometimes accused early Christians of cannibalizing infants during their secret ceremonies (a horror-show misreporting of the Christian Mass?) Later on, medieval Christians sometimes accused Jews of murdering Christian infants and mixing their blood into Passover matzohs. In response to such libels, anthropologists have sometimes swung to the opposite extreme, occasionally even denying that cannibalism (other than emergency survival cannibalism) was ever an established practice. But there is no doubt that human populations have sometimes practiced cannibalism, sometimes in the very recent past. In 1961, for example, Michael Rockefeller, traveling in search of tribal art, was killed and eaten by a group on the coast of New Guinea.
At the Grand Dolina site in the Sierra de Atapuerca in northern Spain, the fragmentary remains of 6 people, mostly children, were discovered mixed in with animal bones and stone tools. Animal and human remains were treated the same. In both cases, cut marks show that flesh was cut from the bones. There’s no evidence that the human remains received any specially respectful treatment. Cannibalism is the most plausible explanation.
The researchers involved have proposed a new species name, Homo antecessor, for these and some other early European finds, although not everybody buys this.