Ardi overturns the savanna story
A skeleton that walked upright and still climbed like an ape
Quick facts
- Age
- About 4.4 million years old
- Found
- 1992 to 1994, Middle Awash, Ethiopia, led by Tim White; announced 2009
- Anatomy
- Grasping big toe, short broad pelvis, backward-bending wrists (no knuckle-walking)
- Challenged
- The savanna theory of why bipedalism evolved
What happened
Between 1992 and 1994, a team led by paleoanthropologist Tim White found the first Ardipithecus ramidus fossils in the Middle Awash region of Ethiopia, but it was not until 2009 that the team announced their most important find: a partial skeleton nicknamed Ardi, about 4.4 million years old and one of the most complete early human skeletons ever recovered. Ardi's feet had an opposable, grasping big toe alongside more rigid remaining toes, her pelvis was short and broad, and her wrists could bend backward in a way chimpanzees and gorillas, built for knuckle-walking, cannot. Together, the Smithsonian describes this as a mosaic: she could walk upright on the ground while still moving carefully on top of branches using all four limbs, a gait called palmigrady, rather than swinging or knuckle-walking like a chimp.
Why it matters
Ardi's fossils turned up alongside evidence that she lived in a wooded environment, not open grassland, directly contradicting the long-standing theory that bipedalism evolved as forests gave way to savanna. Her anatomy also suggested the last common ancestor of humans and chimpanzees was not itself chimpanzee-like, reshaping how scientists picture the starting point of the whole human lineage.
How we know
The Smithsonian's Ardipithecus ramidus species page and its dedicated page on the Ardi skeleton give the 1992 to 1994 discovery by Tim White's team, the 2009 announcement, the wooded habitat and its challenge to the savanna hypothesis, and the specific foot, pelvis, and wrist anatomy. The Smithsonian is explicit that Ardi's pelvis was reconstructed from crushed fossils and that some scientists consider it only suggestive, not conclusive, of bipedalism, so this event is marked debated rather than settled.
Sources
- Smithsonian Institution. Ardipithecus ramidus (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)
- Smithsonian Institution. ARA-VP-6/500, 'Ardi' (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)
- White et al.. Ardipithecus ramidus and the paleobiology of early hominids (Science, 2009, via PubMed) (2009) · Peer-reviewed (author-declared)pubmed.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)
See something wrong? . Corrections with a source get fixed fastest.
Part of a timelineHuman Evolution12 events · Seven million years from the last ancestor we shared with other apes to the species writing this sentence.View all →