A sculpture of “Lucy”, a 3.2 million-year-old Australopithecus afarensis hominin, along with a baby and other group members on display at the Houston Museum of Natural Science in 2007.
About 3.2 million years ago, our ancestor “Lucy” roamed what is now Ethiopia. The discovery of her fossil skeleton 50 years ago transformed our understanding of human evolution. But it turns out her species, Australopithecus afarensis, wasn’t alone. In fact, as many as four other kinds of proto-humans roamed the continent during Lucy’s time.
For almost a million years, A. afarensis lived throughout East Africa, and paleoanthropologists have found numerous fossils of this species ranging from north central Ethiopia to northern Tanzania — a span of 1,460 miles (2,350 kilometers), or roughly the distance from Boston to Miami.
“It was a highly successful species that was comfortable in lots of different habitats,” Donald Johanson, a paleoanthropologist at Arizona State University, told Live Science.
For decades after Lucy’s discovery, paleoanthropologists assumed A. afarensis was the only hominin that lived in this region during the middle Pliocene epoch (3 million to 4 million years ago). But the discovery of a fragmentary jawbone in the Bahr el Ghazal region of Chad in 1995 dramatically changed the picture of hominin diversity.
At 3.5 million years old, this fossil of a species that would be named Australopithecus bahrelghazali was the first indication that other hominins lived around Lucy’s time. Lucy’s kind may not have interacted with these australopithecines, who were more than 1,500 miles (more than 2,400 km) away. But at the site of Woranso-Mille, just 30 miles (48 km) north of where Lucy was found at the site of Hadar in Ethiopia, Haile-Selassie and colleagues found A. afarensis fossils along with other, anatomically distinct fossils from the same time period.
These fossils belonged to a new australopithecine species: Australopithecus deyiremeda, which was dated to between 3.5 million and 3.3 million years ago. A. deyiremeda had markedly different teeth than Lucy’s species, suggesting they had different diets, but paleoanthropologists do not currently agree on whether it is a different species from Lucy.
The discovery of multiple hominin species raises the question of whether they interacted or even mated with each other. While some researchers believe there is morphological evidence consistent with hybridization in A. afarensis, the exact nature of their interactions remains uncertain.
Despite the vast number of A. afarensis fossils discovered over the past half century, paleoanthropologists still have many unanswered questions about the relationships and interactions among different hominin species. Further research using ancient proteins may provide more insights into how these proto-humans lived alongside each other in ancient Africa.
