An international research team led by scientists from La Trobe University in Australia and the University of Cambridge is questioning how one of the most complete early human fossils has been classified. Their findings suggest the specimen may not belong to any known human ancestor species and could represent an entirely new one.
The fossil, uncovered in South Africa’s Sterkfontein Caves in 1998 and nicknamed “Little Foot,” has long been considered part of the Australopithecus genus. This group includes early, upright-walking relatives of humans that lived in southern Africa between about 3 million and 1.95 million years ago.
Ronald Clarke, the paleoanthropologist who led the painstaking 20-year effort to excavate and study the skeleton, initially identified Little Foot as Australopithecus prometheus when it was formally introduced in 2017. Other researchers argued it belonged to Australopithecus africanus, a species first described in 1925 by Australian anatomist Raymond Dart and already known from the same region.
New Evidence Challenges Old Assumptions
In a peer-reviewed study published in the American Journal of Biological Anthropology, a team led by La Trobe University adjunct Dr. Jesse Martin reached a different conclusion. Their analysis found that Little Foot does not share a distinct combination of features with either Australopithecus prometheus or Australopithecus africanus. This opens the door to the possibility that the fossil represents a previously unrecognized species.
“This fossil remains one of the most important discoveries in the hominin record and its true identity is key to understanding our evolutionary past,” Dr. Martin said.
“We think it’s demonstrably not the case that it’s A.prometheus or A. africanus. This is more likely a previously unidentified, human relative.
“Dr. Clarke deserves credit for the discovery of Little Foot, and being one of the only people to maintain there were two species of hominin at Sterkfontein. Little Foot demonstrates in all likelihood he’s right about that. There are two species.”
Why Little Foot Matters
Formally known as StW 573, Little Foot is still considered the most complete ancient hominin skeleton ever found. Despite its significance, no team had publicly challenged its species classification since its debut in 2017 until now.
“Our findings challenge the current classification of Little Foot and highlight the need for further careful, evidence-based taxonomy in human evolution,” Dr. Martin said.
Dr. Martin, who holds an adjunct position at La Trobe University and is a postdoctoral research fellow at Cambridge, will continue this work alongside La Trobe students. Their goal is to determine exactly which species Little Foot belongs to and where it fits within the broader human family tree.
Broader Implications for Human Evolution
The research was conducted under an Australian Research Council grant led by Professor Andy Herries at La Trobe University. Professor Herries emphasized the fossil’s importance for understanding early human diversity and how ancient relatives adapted to the varied environments of southern Africa.
“It is clearly different from the type specimen of Australopithecus prometheus, which was a name defined on the idea these early humans made fire, which we now know they didn’t. Its importance and difference to other contemporary fossils clearly show the need for defining it as its own unique species.”
The study reflects a wide-ranging collaboration among researchers and institutions in the United Kingdom, Australia, South Africa and the United States.