The first clue that the fossilized human ancestor known as Lucy was a global phenomenon appeared at a Paris airport in December 1974. While passing through customs, paleoanthropologist Donald Johanson presented the packages packed in his bag as fossils from Ethiopia, and a customs officer replied, “You mean Lucy?

A few weeks earlier, Johanson and his team had discovered the bones of a small adult female, who appeared to be a long-lost member of our family tree. The ancient skeleton had not yet been examined and analyzed by researchers, but a press release was enough to propel it to the status of the best-known fossil in history.

At the time, there was “a lot of interest in human origins,” Johanson says. Discoveries by the Leakey family and other South African scientists have begun to enrich human history, suggesting that early ancestors developed an upright posture millions of years ago in Africa, followed later by big brains and the ability to use tools.

Yet the fossils discovered so far have been fragmentary: a skull here, a partial foot there. And they were no more than 1.75 million years old, significantly younger than what was thought to be humans’ most distant ancestors.

Lucy would set records for age and completeness, while confirming ideas about humans’ evolutionary transition to upright walking. Since then, other fossils have surpassed her in terms of accomplishments, but Lucy remains a household name 50 years later. The scientific history of the fossil is from the beginning closely linked to a cultural history.

The story of Lucy’s discovery

On November 24, 1974, Johanson was searching for fossils of ancient human or hominid relatives in an area called Hadar, in the Afar region of Ethiopia, when he noticed a forearm bone eroding into the side of a hill. Retrieving the bone and returning to camp, Johanson and the grounds crew celebrated by singing the popular Beatles song, “Lucy in the Sky With Diamonds” (or so the story goes). The next day, they excavated the remaining hominid remains in 110-degree heat and began calling the skeleton Lucy. In scientific circles it would later be known as AL288-1and in Ethiopia, like Dinkinesh, which means “you are wonderful” in Amharic.

By piecing together her lower jaw, skull fragments, vertebrae, ribs, arms, pelvis and legs, the team collected about 40 percent of Lucy’s skeleton. She appeared to be a fully grown adult, but was just over three feet tall.

(Here’s a theory on how Lucy died.)

The layers of volcanic rock that sandwich the fossils date it to 3.2 million years ago, almost double the age of what was then the oldest known human ancestor. Beyond that, the next oldest skeleton of the time was only 100,000 years old. Such an ancient and complete specimen was remarkable. Lucy hits all the superlatives, scientific editor for the New York Times Boyce Rensberger remembers it as “the oldest and most complete.”

Based on the fragmented remains of her skull and other discoveries at Hadar, Lucy appeared to have a small, chimpanzee-sized brain and a protruding face, but the rest of her skeleton indicated a completely upright posture, similar to that of a human. In 1978, Johanson and his colleagues officially assigned it to a new species, Australopithecus afarensis (the southern Afar monkey in Latin), and said she was proof that our ancestors walked on two legs before developing large brains.