Lucy: The 3.2-Million-Year-Old Australopithecus Skeleton

Lucy is the nickname of a 3.2-million-year-old partial skeleton of Australopithecus afarensis found at Hadar in Ethiopia on 24 November 1974 by the American palaeoanthropologist Donald Johanson and his student Tom Gray. About 40 per cent complete, it was the most complete early hominin skeleton then known. Lucy showed that human ancestors walked upright long before they developed large brains, and she became the most famous fossil in the study of human origins.

Background: the race to find early hominins

In the 1960s and early 1970s, discoveries by the Leakey family at Olduvai Gorge and Lake Turkana had made East Africa the centre of research into human origins. Most known hominin fossils older than 2 million years were fragments: teeth, jaws and pieces of skull. Very little was known about how the earliest hominins walked.

In 1973 the French geologist Maurice Taieb, Donald Johanson, the French palaeontologist Yves Coppens and the American geologist Jon Kalb organised the International Afar Research Expedition to explore Hadar, an area of badlands along the Awash River in Ethiopia’s Afar region. Taieb had recognised that its eroding layers of sediment, rich in fossils, dated to around 3 million years ago.

In the first season, in 1973, Johanson found a hominin knee joint (catalogued as AL 129-1). The angle between the thigh bone and shin bone matched that of an upright walker, as in humans, rather than an ape. This was a tantalising clue, but a single joint could not reveal the whole body.

Discovery on 24 November 1974

On the morning of 24 November 1974 Johanson and Tom Gray were mapping fossil localities in a gully known as Afar Locality 288. On their way back to the Land Rover, Johanson noticed a small piece of arm bone on a slope. Nearby lay fragments of skull, a thigh bone, ribs, vertebrae and part of a pelvis. They quickly realised the pieces might belong to a single individual.

That evening the camp celebrated. A tape recorder played the Beatles song “Lucy in the Sky with Diamonds” over and over, and the skeleton became Lucy. Ethiopians later gave her the Amharic name Dinkinesh, meaning “you are marvellous”. Over the next three weeks the team collected several hundred fragments of bone, which together represented about 40 per cent of one skeleton. Her formal catalogue number is AL 288-1.

Because there were no duplicated bones and all came from a small creature of the same size and age, the team concluded that they belonged to one individual. Her wisdom teeth had erupted and were slightly worn, showing she was an adult, though a young one.

The First Family and a new species

In 1975 the expedition found an even richer site, AL 333, nicknamed the “First Family”. It produced more than 200 hominin fossils from at least 13 individuals, adults and juveniles, perhaps buried together in a single event. Together with Lucy, these bones gave an unprecedented picture of one early hominin population.

Johanson worked with the American palaeoanthropologist Tim White, who had studied similar fossils from Laetoli in Tanzania. They concluded that the Hadar and Laetoli hominins belonged to a single new species. In 1978 Johanson, White and Coppens named it Australopithecus afarensis, after the Afar region. Somewhat surprisingly to many readers, the type specimen chosen for the species was not Lucy but a lower jaw from Laetoli, known as LH 4.

What Lucy’s skeleton shows

Lucy was small. She stood about 1.1 metres tall and probably weighed around 29 kilograms. Males of her species appear to have been considerably larger, a difference between the sexes greater than in modern humans.

Built for walking

Her pelvis was short and broad, shaped more like a human’s than an ape’s, so that the hip muscles could keep her balanced on one leg at a time when walking. Her thigh bone angled inward towards the knee, placing her feet beneath her body, as in humans. Her lower spine had the inward curve that helps humans stay upright. Together with the Laetoli footprints, made by the same species about half a million years earlier, Lucy’s skeleton proved that Australopithecus afarensis walked habitually on two legs.

Still at home in trees

In other ways Lucy was ape-like. Her arms were relatively long compared with her legs, her finger bones were curved, and her shoulders were adapted to raising the arms overhead. A 2016 study of the internal structure of her arm bones found them stronger than those of modern humans, suggesting she still spent considerable time climbing. Many researchers think the species walked on the ground but sheltered and fed in trees.

A small brain

Only fragments of Lucy’s skull survive, but other skulls of her species show brains of roughly 380 to 550 cubic centimetres, about a third of the size of a modern human brain and only somewhat larger than a chimpanzee’s. Her face projected forward, and her teeth combined fairly large molars with smaller canines than those of apes.

The central lesson was clear: upright walking came first, and the great expansion of the brain came much later, beginning with early Homo such as Homo habilis more than a million years after Lucy.

Dating Lucy

Hadar’s sediments include layers of volcanic ash, which can be dated by measuring the decay of potassium into argon. Early estimates for Lucy varied, but refined argon-argon dating of ash layers above and below the fossil-bearing sediments places her at about 3.18 to 3.2 million years old. Fossils of Australopithecus afarensis as a whole range from about 3.85 to 2.95 million years ago.

How did Lucy die?

In 2016 a team led by John Kappelman published a study in Nature based on CT scans of Lucy’s bones. They argued that compressive fractures in her arm, shoulder and other bones were consistent with a fall from a height of more than 12 metres, perhaps from a tree. Johanson, White and others disagreed, noting that many fossils show similar breaks caused by the weight of sediment and by erosion long after death. The cause of her death remains unknown. What is clear is that her body came to rest near a stream or lake margin, where it was covered by sand and silt quickly enough for much of the skeleton to survive, while some bones were lost to scavengers, water or later erosion.

Debates about Lucy’s place in the family tree

For many years after 1978, Australopithecus afarensis was widely presented as the common ancestor of later hominins, including both the robust australopithecines and the genus Homo. This view remains influential but is no longer unchallenged.

Later discoveries have shown that the period was more crowded than once thought. Older hominins such as Ardi push the story further back. Other species lived alongside afarensis, possibly including Kenyanthropus platyops in Kenya and Australopithecus deyiremeda in Ethiopia. In 2015 a 2.8-million-year-old jaw from Ledi-Geraru, not far from Hadar, was described as the earliest known member of the genus Homo, which fits the idea that Homo emerged from a population similar to Lucy’s, but does not prove it.

Fame and travels

Johanson’s popular book, written with Maitland Edey and published in 1981 as Lucy: The Beginnings of Humankind, made her a household name. She appeared in textbooks, documentaries and museum displays around the world, usually as a cast.

The original bones are kept at the National Museum of Ethiopia in Addis Ababa. Between 2007 and 2013 they toured museums in the United States, starting at the Houston Museum of Natural Science. The tour was controversial: some scientists and museums argued that such a fragile and important fossil should not travel, while the Ethiopian government hoped to raise the country’s profile and support its museums. In 2025 the originals were displayed in Europe for the first time, at the National Museum in Prague, alongside the juvenile afarensis skeleton known as Selam, found at Dikika in 2000.

By the numbers

Timeline

• 1973: The International Afar Research Expedition begins work at Hadar; Johanson finds the AL 129-1 knee joint.
• 1974, 24 November: Johanson and Tom Gray find Lucy at Afar Locality 288.
• 1975: The “First Family” site AL 333 is discovered.
• 1978: Johanson, White and Coppens name Australopithecus afarensis.
• 1981: Johanson and Edey publish Lucy: The Beginnings of Humankind.
• 2006: The juvenile afarensis skeleton Selam, found at Dikika, is published.
• 2007–2013: Lucy’s original bones tour the United States.
• 2016: A study proposes that Lucy died from a fall, a claim others dispute.
• 2025: The original fossils are exhibited in Prague, their first display in Europe.

Why it matters

Lucy transformed the study of human origins by showing, for the first time in a single skeleton, what an early hominin body looked like. She demonstrated that our ancestors stood and walked upright while their brains were still small, overturning older assumptions that a large brain led the way. Half a century after her discovery, she remains the reference point against which most other early hominin finds are measured.