‘A complete surprise’: Homo erectus skull discovered in China is almost 1.8 million years old, the oldest evidence of ancient human relatives in East Asia

Three Homo erectus skulls previously unearthed in China are about 1.8 million years old, making them about 600,000 years older than originally thought, a new study has found.

The new findings make the Unxian skull of Hubei the oldest evidence of early relatives of humans, known as hominins, in East Asia, according to a study published Wednesday (February 18) in the journal Science Advances.

Study co-author Christopher Bay, a professor of anthropology at the University of Hawai’i at Mānoa, told Live Science in an email that he was “completely surprised” when he first saw the results. This older age may cause experts to reconsider the date when H. erectus first appeared, which is thought to have originated in Africa about 2 million years ago.

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“This means we need to consider pushing the origins of Homo erectus back to about 2.6 million years ago,” Bae said in an email.

Homo erectus has long been thought to be the first human relative to leave Africa, and the 1.78 million to 1.85 million year old fossils found at the Dmanisi site in Georgia are the earliest evidence of humans in Asia. However, 2.1- and 2.43-million-year-old stone tools discovered at two sites in China complicate the situation, as they are older than experts’ theories about the origin of Homo erectus.

The exact age of the three Unzen skulls, discovered between 1989 and 2022, has long been debated, but they were previously thought to be about 1 million years old based on the age of animal teeth found nearby, although one study used electron spin resonance and uranium-based dating to place them at about 1.1 million years old. So when the opportunity arose to try a new dating technique in the field, Bae and his colleagues thought it was a good time to revisit the argument.

Their team used a technique called cosmogenic nuclide burial dating to determine the age of quartz found in the sedimentary layer where the skull was discovered. This dating technique measures the half-lives of two chemical variants (aluminum-26 and beryllium-10) to determine how long a crystal has been exposed to cosmic rays.

This dating method determined that the hominin fossils were about 1.77 million years old, which is about 600,000 years older than the earliest date previously proposed for the site, Bae said.

He added that the new age is younger than stone tools found elsewhere in China, so there is still a large time gap of about 600,000 years between the oldest fossil evidence and the earliest tool evidence.

However, since this age is similar to the Dmanisi fossil in Georgia, the results suggest that Homo erectus migrated across Asia relatively quickly, Bae said. However, the size and shape of the Yunxian skulls indicate that these hominins had larger brains than the hominins found at Dmanisi, despite being relatively similar in age. “This points to an important variation in early humans outside of Africa,” Karen Barb, a professor of anatomy at Midwestern University in Illinois who was not involved in the new study, told Live Science in an email.

Chris Stringer, a paleoanthropologist at the National History Museum in London, who was not involved in the new study, told Live Science in an email that “it would certainly be surprising” if the Unzen skull was nearly 1.8 million years old, but “putting Unzen at something this old would be completely out of sync with the rest of the fossil record.”

Previous research by Stringer and his colleagues suggested that the Unzen fossils may belong to the group that gave rise to Denisovans, and their model suggests that Denisovans emerged about 1.2 million years ago.

Stringer said if the new date of the Unzen fossil is correct, experts may need to reconsider the ancestral origins of our own species, Homo sapiens. “I think more research is definitely needed into the dating of this site.”

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