ANKARA

One of the world’s most complete early human fossils, known as Little Foot, may represent a previously unidentified species of human ancestor, according to a new Australian-led study that challenges long-standing assumptions about early human evolution, media reports said Sunday.

Little Foot, a near-complete hominin skeleton discovered in South Africa’s Sterkfontein cave system, was publicly unveiled in 2017 after more than 20 years of excavation and preparation, according to British daily The Guardian.

The fossil was originally attributed to Australopithecus Prometheus by its discoverer, while other researchers have argued it belongs to Australopithecus africanus, a species first identified in 1925 from the same cave complex.

However, a new study published in the American Journal of Biological Anthropology suggests that Little Foot does not fit neatly into either classification.

“We think it is a formerly unknown, unsampled species of human ancestor,” said lead author Jesse Martin, an adjunct researcher at La Trobe University and a postdoctoral fellow at the University of Cambridge.

Martin said the skeleton shows anatomical traits that distinguish it from both Australopithecus Prometheus and Australopithecus africanus.

“It doesn’t look like Australopithecus Prometheus, but it also doesn’t look like all of the africanus to come out of Sterkfontein,” he said.

The researchers identified notable differences at the base of the skull, including a longer nuchal plane, a feature generally considered stable across human evolution.

“The bottom back of the skull is supposed to be fairly conserved in human evolution,” Martin said, adding that variation in this area is more likely to signal a distinct species.

The study suggests the findings could point to an entirely new branch in the human family tree.

“This thing will be part of a lineage of hominins,” Martin said. “It’s possible that we have not just a point in our human family tree we hadn’t discovered before, but an entire limb.”

The authors stopped short of formally naming a new species, saying that decision should be left to the team that excavated and studied Little Foot over more than two decades.

There is also an ongoing debate over the fossil’s age. While it is commonly estimated to be 3.67 million years old, some researchers argue it may be closer to 2.8 million years.