Human evolution wasn't a straight line — it's a bush with many extinct branches. The surprising truth: bipedalism evolved millions of years before large brains or tool use. Drag the slider to explore how cranial capacity increased across the Homo lineage.
Drag to see brain size change across hominin species
Bipedalism appeared around 6–7 million years ago in early hominins like Sahelanthropus and Ardipithecus, long before the Homo genus emerged. Walking upright freed the hands and changed energy efficiency, but brain size remained chimpanzee-like (around 400–500 cm³) for millions of years. Only with the appearance of Homo habilis around 2.4 million years ago did cranial capacity begin increasing noticeably, eventually tripling to modern Homo sapiens levels of ~1350 cm³. Tool use followed brain expansion — the oldest stone tools date to 3.3 million years ago, but sophisticated toolmaking correlates with larger brains in the Homo lineage.
Hominins are the group including humans and our extinct bipedal relatives — bipedalism evolved long before large brain size, and cranial capacity increased across the Homo lineage from ~600 cm³ in early Homo to ~1350 cm³ in modern humans.