Australopithecus afarensis
Confidently bipedal on the ground — and the maker of footprints frozen in ash.
Overview
Australopithecus afarensis is the best-known early hominin, thanks to the 1974 discovery of Lucy — about 40% of a single skeleton — and the haunting Laetoli footprints, a trail of upright tracks pressed into volcanic ash 3.6 million years ago.
For nearly a million years this species thrived across eastern Africa, making it one of the most successful hominins ever and a leading candidate for the ancestor of our own genus.
Anatomy & Body
From the neck down, A. afarensis was committed to walking upright: a bowl-shaped pelvis, angled thigh bones and arched feet are all hallmarks of bipedalism. Yet curved fingers and toes and long arms reveal that it still climbed trees, probably for food and safe sleep.
It was strongly sexually dimorphic — males up to ~150 cm and females closer to ~105 cm — with an ape-like, forward-projecting face and a brain only modestly larger than a chimpanzee's.
Brain & Cognition
Brain volume of 380–430 cc is just above the chimpanzee range. Some endocast features hint at a slightly reorganised, slower-developing brain, but cognition was still broadly ape-grade.
Behavior & Culture
A. afarensis ate a flexible diet of fruits, leaves, seeds and possibly some meat. Cut-marked animal bones from Dikika hint — controversially — that members of this species may have used stone to access meat, though clear stone tools appear only later.
Key Fossils
- A.L. 288-1 (“Lucy”) — the iconic partial skeleton from Hadar, Ethiopia.
- The Laetoli footprint trail (Tanzania) — direct evidence of upright walking.
- DIK-1-1 (“Selam”/“Lucy's child”) — a remarkable juvenile skeleton.
Relationship to Us
Most researchers place A. afarensis at or near the base of the lineage that led to Homo, making Lucy something close to a great-great-grandmother of humanity.