One of the most complete human ancestor fossils ever found could be an entirely new species, according to a new study.

The fossil, found in South Africa’s Sterkfontein Caves in 1998 and dubbed “the Little Foot”, was widely believed to be a member of the *Australopithecus *genus of ape-like upright-walking human ancestors that lived between 3 million and 1.95 million years ago.

When the fossil was first unveiled to the world in 2017, it was attributed to the species Australopithecus prometheus*. *However several experts maintained that it belonged to Australopithecus africanus.

Now, a new study suggests that Little Foot doesn’t share unique traits with either species, raising the possibility that it may represent an altogether new 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,” said anthropologist Jesse Martin from La Trobe University.

“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,” said Dr Martin, an author of the new study published in the American Journal of Biological Anthropology.

“Our findings challenge the current classification of Little Foot and highlight the need for further careful, evidence-based taxonomy in human evolution.”

Jesse Martin holding a 3D print of the Little Foot skull (La Trobe University)

“We find that the morphology preserved by StW 573 doesn’t support assigning that specimen to A prometheus because it does not share a unique suite of primitive and derived traits in common with the A prometheus type specimen MLD 1,” researchers said in the latest study.

In future studies, scientists hope to test and clarify which species Little Foot represents and where that species sits in the human family tree.

"It is clearly different from the type specimen of Australopithecus prometheus, which was a name defined on the idea that these early humans made fire, which we now know they didn’t,” said anthropologist Andy Herries, another author of the study.

“Its importance and difference to other contemporary fossils clearly show the need for defining it as its own unique species.”