Little Foot and the Problem of Naming Our Ancestors

A Fossil That Refuses to Behave

Few fossils have inspired as much patience, devotion, and disagreement as StW 573, better known as Little Foot. Encased in breccia deep within South Africa’s Sterkfontein cave system, the skeleton took more than two decades to excavate. When it was formally presented to the world in 2017, it immediately earned superlatives. It is the most complete early australopith skeleton ever found, preserving not just a skull but limbs, hands, feet, and a near complete body plan of a hominin that walked southern Africa millions of years ago.

Completeness, however, does not guarantee clarity. From the moment Little Foot emerged, paleoanthropologists began arguing over a deceptively simple question: what species does it belong to?

Ronald Clarke, who led the excavation, argued that Little Foot represented Australopithecus prometheus, a species first proposed in the mid twentieth century and long treated by many researchers as indistinguishable from Australopithecus africanus. Others countered that Little Foot was simply an unusual member of Australopithecus africanus, a species known from the same cave system since 1925.

Dr Jesse Martin of LaTrobe University thinks Little Foot could be a whole new branch of the human family tree. Photograph: La Trobe University

Now a new analysis¹ led by Jesse Martin and colleagues suggests that both camps may be wrong. Little Foot, they argue, is neither Australopithecus africanus nor Australopithecus prometheus, but something else entirely.