Bold claim: Little Foot may be a completely new human-ancestor species, not fitting neatly into existing Australopithecus categories. This is the core idea driving a fresh look at one of the most complete hominin fossils ever found.
Little Foot, viewed by many as the most complete Australopithecus skeleton, has long sparked debate about its exact classification. The fossil’s foot bones—hence the name—were first uncovered in South Africa in 1994, with a meticulous excavation spanning two decades within the Sterkfontein cave system.
Led by paleoanthropologist Prof. Ronald Clarke of the University of the Witwatersrand, the team has historically linked Little Foot with Australopithecus prometheus. Others in the field have argued for Australopithecus africanus, a species described in 1925 and also discovered in the Sterkfontein area.
Australopithecus, meaning “southern ape,” denotes a group of early human ancestors who inhabited Africa as far back as about 4.2 million years ago.
A new study led by Australian researchers and published in the American Journal of Biological Anthropology raises the possibility that Little Foot does not neatly align with either of those two species. The researchers propose that the fossil may represent a previously unknown, unsampled species of human ancestor.
“We think it is a formerly unknown, unsampled species of human ancestor,” stated Dr. Jesse Martin, an adjunct at La Trobe University in Melbourne who led the research. He noted that Little Foot “doesn’t look like Australopithecus prometheus … but it also doesn’t look like all of the africanus to come out of Sterkfontein.” Martin, who is also a postdoctoral fellow at the University of Cambridge, suggested that this fossil could reveal not just a single missing link but an entire branch of the human family tree.
Martin highlighted Clarke’s unusual stance—that there were two coexisting hominin lineages at Sterkfontein—and said the new work aligns with the possibility that one lineage is distinctly separate from prometheus.
The researchers argue that distinctive skull features help separate Little Foot from Australopithecus africanus, notably a longer nuchal plane at the back of the skull. Martin explained that the base of the cranium tends to be relatively stable over evolutionary time; when differences appear there, they are more likely to signal distinct species. All of the notable differences observed in this study are located in that region.
“Finding evidence hiding in plain sight at Sterkfontein of an entirely new species is both remarkable and counterintuitive,” Martin remarked, especially given that Little Foot is the most complete early human fossil in the record. He emphasized the expectation that researchers will soon clarify where this specimen sits on the human family tree.
The authors stop short of officially reclassifying Little Foot, suggesting instead that naming a new species should be undertaken by the long-time excavation team responsible for the specimen. They present their ideas as thoughtful guidance, hoping the core team will consider their perspective in due course.
There is ongoing debate over the fossil’s age. Estimates place Little Foot at about 3.67 million years old, though some researchers contend it cannot be older than roughly 2.8 million years.
Ronald Clarke, the lead discoverer, has been approached for comment on these new interpretations.
