When did humans first start eating each other?

Brazil. Engraving by Theodor de Bry for Hans Staden's account of his 1557 captivity.

Anthropological data shows that millions of years ago, Homo antecessor, the link between Neanderthals and Homo sapiens, were cannibalistic for nutritional reasons. Humans eventually developed more advanced hunting techniques in order to prey on animals since consuming each other was not a sustainable food source.

In 1492, when Columbus came to the Americas, he encountered the West Indies Carib tribe, who were ritually cannibalistic. The explorers mispronounced their name and called them Canibs instead of Caribs. According to Merriam-Webster the first known-use of the word cannibal was in 1553.

From the 16th through 18th centuries, blood, ground bones and other body parts were routinely used in what is referred to as medicinal cannibalism. Through cannibalism's history there has been a persistent theme that the vitality of the human body and spirit can be ingested to bestow power and life force upon human beings.

In the 20th century instances of survival cannibalism are known to have occurred in China up through the 1960s and even in North Korea more recently.