A Cave Fossil in South Africa Suggests Homo Erectus Is 200,000 Years Older

A newly analyzed fossil from a cave site in South Africa suggests that Homo erectus, an early human ancestor, appeared in southern Africa about 2 million years ago. That is roughly 200,000 years earlier than the species' emergence was previously placed, according to ScienceAlert's report on the study, which appeared in the journal Annals of Human Biology.

The work was carried out by an international team and centers on Drimolen Main Quarry near Johannesburg, part of the area known as the Cradle of Humankind. The same study also describes a large set of fossils from a more distant relative, Paranthropus robustus, offering a rare look at two ancient species that lived side by side.

What the researchers found

The new specimen, catalogued as DNH 127, is an adult fossil attributed to Homo erectus. Jesse Martin, an archaeologist at La Trobe University in Australia, said it provides further confirmation that the species first appeared in southern Africa 2 million years ago.

The earlier date is not entirely new. A skull fragment known as DNH 134 had already been dated to the same period. But that fossil came from a young child, which makes comparisons with adults difficult. An adult specimen from the same time gives researchers a more direct point of comparison.

In total, the team analyzed 18 fossils. Species were identified from the physical characteristics of the bones, while geological methods, including radioactive dating, were used to estimate their ages. Besides the single Homo erectus fossil, the researchers linked 14 fossils to Paranthropus robustus.

A second species that outnumbered our ancestors

Paranthropus robustus sits farther from humans on the family tree than Homo erectus does. It had heavy jaws and large teeth suited to processing hard, tough food. According to the report, while Homo erectus was developing larger brains and smaller teeth, the teeth of Paranthropus robustus were growing bigger and its chewing muscles stronger, as the shape of its jaws shows.

Martin said the two species shared the same landscape and are both preserved in the Drimolen cave. Homo erectus and the lineage leading to modern people eventually prevailed, he said, but 2 million years ago Paranthropus robustus outnumbered Homo erectus at the site by more than 10 to one. He described our ancestors at that time as looking like an outside, long-odds chance to survive.

The Paranthropus robustus fossils also support the idea that the species was changing over time. Specimens found at other sites point to larger, stronger individuals, a sign of that evolution. The new fossils revealed jaw features not seen before and several areas of variation. Martin said the large number of fossils from Drimolen allows an unprecedented look at the small-scale evolutionary changes that shaped human ancestors.

Why it matters

Homo erectus, whose name translates to upright human, was the first hominin to show signs of adapting to life on the ground, with longer legs and shorter arms. Dating the species correctly therefore matters for understanding how and where our own lineage took shape.

The study also adds detail to a picture scientists already knew was complicated: ancient human ancestry was not a single line, but involved several species overlapping in different places. This research adds clarity for two of them in the Drimolen region.

What remains uncertain

ScienceAlert noted that the fossils involved are relatively small fragments, and that further investigation will be needed to confirm the presence of Homo erectus and Paranthropus robustus this far back in time. The site has produced many fossils, and more are likely to be uncovered. Those finds may help explain why the Paranthropus robustus line eventually died out, while Homo erectus likely led on to modern humans.

Around Prague, based on reporting by ScienceAlert