One day in the summer of 1924, an anthropologist named Raymond Dart made an incredible discovery — and drew a conclusion from it about human nature that would mislead us for a century.

Dart was examining a set of fossils that had been unearthed by miners near the town of Taung in South Africa when he found the skull of a “missing link” between ancient apes and humans. It belonged to a juvenile member of the species Australopithecus africanus who was later nicknamed the Taung Child.

The skull conclusively demonstrated that Africa was the birthplace of humankind. It also seemed to reveal something sinister about human nature: There was a series of grooves etched in the bone, which Dart believed could be produced only by human-made tools. These marks convinced him that this young hominid had been butchered and eaten by another member of its tribe (perhaps a hungry uncle).

Our ancestors, Dart concluded, were cannibalistic killers. He argued that Australopithecus africanus represented a “predatory transition” in which our ancestors evolved from eating plants and fruits to devouring meat — and one another.

Dart’s thesis quickly became scientific consensus, and other anthropologists found facts to support the theory that humans evolved as ruthless hunters. For instance, we can run long distances (presumably to exhaust prey), throw objects with accuracy (to kill prey with spears) and work well together (to coordinate killing prey).

The idea that humans are natural-born predators was not just a scientific claim; it also found expression in the broader culture. In the 1954 novel “Lord of the Flies,” a group of school-age boys stranded on an island descend into savage violence, revealing their true nature. The 1968 movie “2001: A Space Odyssey” begins with a tribe of prehistoric apes — our ancestors — discovering how to use a leg bone as a weapon to assault one another. Today, self-help gurus argue that we should reconnect with our “ancestral lifestyle” of eating raw meat and organs.