Human cannibal ancestors killed each other and ate each other because it was "more profitable" than catching animals, a new study says.
The researchers found archaeological evidence in Spain that was said to show "indisputable signs of cannibalism" in an ancient human species called Homo antecessor and Neanderthals.
The badysis revealed that cannibalism was a good survival technique for the predecessors of Homo sapiens, since they would have had to spend much less time and energy to catch other humans than the fastest animals, even though animal flesh is more caloric.
The study, published in the Journal of Human Evolution, states that human flesh would have been just as nutritious for primitive people.
The bones of seven individuals who showed evidence of being eaten by humans were found in the archaeological site of Gran Dolina in Spain.
The evidence of being consumed by humans includes teeth marks, cuts and fractures made to expose the bone marrow.
Human remains were found among nine other species of mammals, including deer and 22 individuals that had not been eaten.
Homo antecessor is one of the first known varieties of humans discovered in Europe and lived there about a million years ago.
The lead author of the study, Jesús Rodríguez, said: "Our badyzes show that Homo antecessor, like any predator, selected its prey following the principle of optimizing the cost-benefit balance and also shows that considering only this balance, humans were a "Highly clbadified & type of dam.
"This means that, compared to other dams, you can get a large amount of human food at low cost."
Archaeologists also suggested that cannibals may have eaten members of their own group when they died of other causes.