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How large were Australopithecus brains compared with modern human brains?

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Side view illustration of Australopithecus afarensis, an early human ancestor, shown walking upright with a hairy body and ape-like facial features. A scale beside the figure marks 12 inches and 40 centimeters. — Australopithecus Artist's rendering of *Australopithecus afarensis*, which lived from 3.8 to 2.9 million years ago.

Australopithecus brains were significantly smaller than those of modern humans. While the average brain capacity of Homo sapiens is approximately 1,350 cubic centimeters (cc), the average brain capacity for the genus Australopithecus is estimated at about 440 cc.1

Individual species within the genus also reflect this disparity. For example, Australopithecus africanus had an average brain size of approximately 448 cc, which is much closer to that of a modern chimpanzee (roughly 395 cc) than to that of a modern human. These measurements highlight that, despite their humanlike specializations for bipedalism, australopiths possessed brain volumes substantially lower than those found in modern humans.21