Early humans stand up
Our ancestors begin walking on two legs
Quick facts
- Oldest evidence for walking upright
- About 6 million years ago
- Early example
- Sahelanthropus
- Transition
- Apelike and humanlike movement combined for millions of years
- Mostly bipedal
- By about 4 million years ago
What happened
One of the very first traits that set our lineage apart from other apes was walking upright on two legs. The Smithsonian's Human Origins Program traces the oldest evidence for it back about 6 million years, to early species such as Sahelanthropus that may have walked on two legs. For millions of years afterward, from at least 6 to 3 million years ago, our ancestors combined apelike and humanlike ways of moving, still climbing trees but increasingly walking upright on the ground, before becoming mostly bipedal by around 4 million years ago.
Why it matters
Walking on two legs freed the hands from the work of moving around, and over deep time those free hands went on to carry food, make tools, and eventually build every human thing on this timeline. It is the physical foundation of almost everything that makes our species distinctive.
How we know
The Smithsonian Human Origins Program dates the oldest evidence for walking upright to about 6 million years ago, based on fossil bones, and describes the long transition from combining apelike and humanlike movement to becoming mostly bipedal by about 4 million years ago.
Sources
- Smithsonian Institution. Walking upright (Smithsonian Human Origins Program) (2024) · Reputable sourcehumanorigins.si.edu · The domain "humanorigins.si.edu" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- Earliest evidence of hominin bipedalism in Sahelanthropus tchadensis (peer-reviewed, via PubMed Central) · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- Human Evolution → · Zoom in: the fossils tracing how we came to walk upright