What ‘Lucy,’ One of the World’s Most Important Fossils, Has Taught Scientists in the 50 Years Since Her Discovery

About 3.2 million years ago, among the prehistoric forests of what is now Ethiopia, a small human was folded into the fossil record. No one knows for sure what killed them. Perhaps it was a fall from a tree. A carnivore tooth mark on their hip suggests that they were at least nibbled on after death. But whatever transpired, sediment covered and preserved enough of the body that the bones fossilized. Those remains, excavated 50 years ago, would come to be recognized as one of the most important fossil discoveries ever made, known to the world as “Lucy.”

Anthropologists also refer to the skeleton as AL 288-1. It’s the first known partial skeleton representing one of our early relatives, Australopithecus afarensis. Between 3.9 million and 2.9 million years ago, these early humans lived among the woodlands and forests of eastern Africa, in habitats where saber-toothed cats, elephants with strange tusks, ancient rhinos and other prehistoric beasts roamed. AL 288-1 wasn’t the first of the species to be uncovered, nor the last, but was found at an important turning point in our understanding of human evolution.

“Lucy is one of the first celebrity fossils. Everyone knows, and loves, Lucy,” says science historian Lydia Pyne. In fact, the world knew the skeleton and the species it represented as “Lucy” long before the hominin’s scientific name was established. “She left Ethiopia with that nickname,” Pyne says. She was named Lucy after the Beatles song “Lucy in the Sky with Diamonds,” which the scientist team who found her played after the discovery. Pyne notes that this ancient human relative emerged as a persona which has only more recently been placed in the context of both scientific and evolutionary history.

Colonialist explorations of East Africa started turning up A. afarensis fossils as early as 1939. The naturalists just didn’t know what they were looking at. The bones of the early human, or hominin, were associated with similar, more complete finds in South Africa or casually given names such as “Praeanthropus” and “Meganthropus” but never formally described. And during that time, when anthropology was still starkly affected by racist conceptions of human history, experts often failed to see fossils from Africa as directly relevant to human evolution and instead preferred to focus on human fossils from Europe and Asia.

“The significance of early discoveries were underappreciated,” says paleoanthropologist Ashley Hammond, who is part of the Smithsonian’s Human Origins Program team and is a curator at the American Museum of Natural History. For much of the 20th century, hominin finds made in South Africa and elsewhere were dismissed as unimportant to the origin of our own genus, Homo. When anthropologist Raymond Dart revealed an australopithecine skull called the “Taung child” from South Africa in 1924, for example, other experts insisted that the fossil didn’t have anything to do with our evolutionary history and that our ancestors were to be found elsewhere in Europe or Asia. It took decades for experts to reconsider the importance of Africa to human evolution, with finds such as Homo habilis in Tanzania, named in 1964, emphasizing that there was more to find. “Paleoanthropologists were looking for human origins in Africa in a way that they hadn’t been 50 years before,” Pyne says, which would lead to Lucy’s discovery and the recognition of her species.

For paleoanthropologists to change their views and accept the importance of the australopithecines, however, more fossils were needed. By the 1970s, anthropologists were beginning to recognize that there was not just one Australopithecus species, but many. The fossils indicated that these australopithecines stood and walked upright, despite having some characteristics in the skull and limbs that appeared more ape-like. East Africa seemed like a good place to learn more, with overlapping teams searching Tanzania and Ethiopia for more fossils.

The finds came fast. In 1973, a team led by Maurice Taieb, Donald Johanson and Yves Coppens found a knee joint that indicated the human it belonged to was walking upright, signaling that hominins were walking bipedally earlier than experts thought. The following year, the same team found AL 288-1, Lucy. And in 1975, they found a collection of more than 200 bones representing 13 individual A. afarensis, collectively labeled AL 333. “This is an assemblage of many adults and a few children that died around the same time,” Hammond says, a grouping that helped anthropologists understand the size range and perhaps social lives of the species. A year after that, a different team led by Mary Leakey found early human trackways in rocks of similar age at Laetoli, Tanzania, footprints eventually attributed to A. afarensis. An overlooked early human had become known from a wealth of information.

Lucy’s relative completeness helped make the fossil a star, as well. Early hominins were often known from pieces of jaw, isolated craniums and individual skeletal pieces. A partial skeleton that could say something about the overall form and stature of a single early human was an outstanding find, made at a time long before the current views of early human evolution. “Even though new species were being discovered in the mid-late 20th century, there are still way more species that we know about today,” Pyne says, and the big question surrounding Lucy and her kin was how closely they were related to us.

When AL 288-1 and the AL 333 fossils were officially described for the first time in 1978, they sparked a rethink of human evolution. Australopithecines truly were humans, much more relevant to our ancestry than experts previously thought. Increasing brain size and intelligence didn’t lead the way in our evolutionary transformation as early 20th century anthropologists often assumed. Humans had begun to move bipedally on the ground by at least three million years ago, during a time when they still had long arms and curved fingers suited to moving through the trees. Australopithecus afarensis became a perfect example of a transitional fossil, providing insight into what our hominin predecessors were like and how they moved, even if anthropologists still debate whether the species represents our direct ancestors.

Anthropologists have found A. afarensis fossils elsewhere in East Africa since 1978. In addition to a variety of sites in Ethiopia’s Afar Region, A. afarensis has also been found in Kenya at Koobi Fora. Some A. afarensis, such as DIK-1-1, discovered by Zeresenay Alemseged in 2000 and named “Selam,” are even more complete and detailed than AL 288-1. Together, the bones and tracks reveal hominins that split their time between the ground and the trees that were beginning to become scarcer as the world’s climate grew cooler and drier.

If we were to meet them in life, A. afarensis would have seemed short to us. AL 288-1, for example, would have been about 3 feet 5 inches tall in life, although some A. afarensis would have been about 4 feet 11 inches. Their arms would have seemed long compared to ours, with curving finger bones good for grasping branches as well as food and objects. Their torsos were differently shaped, too, more funnel-like and broadened at the base to meet the flared hips that held the viscera as the humans walked. A. afarensis also had smaller canine teeth than earlier humans and great apes, with molars suited to crushing food. They were likely more herbivorous than later hominins but, much like chimpanzees and other great apes today, wouldn’t turn down meat if it were possible to get.

Despite our familiarity with Lucy and her species, however, a great deal remains that paleoanthropologists still don’t know and are curious about. “I would like to know the biogeographic range of Lucy’s species,” Hammond says. A. afarensis fossils have been found as far south as Tanzania and as far west as Chad, but could they have wandered even farther? Such a broad geographic range might hint that A. afarensis lived in a variety of habitats that ranged from closed and forested to more open and somewhat dry, as well, which has important implications for how anthropologists reconstruct the lives of the hominins.

We’ve named the species and celebrated Lucy as an evolutionary icon, but we are truly just beginning to understand these members of our ancient family.

Riley Black | | READ MORE

Riley Black is the author of The Last Days of the Dinosaurs and many other books. She is a science correspondent for Smithsonian magazine covering fossils and natural history, and she writes about the prehistoric past for a variety of publications.