Ice Age butcher’s tools are a sign of ancient humans’ creativity during hard times

In central China, scientists have spent over a decade excavating and studying an archaeological site where ancient humans butchered animals. Amidst bones, archaeologists found complex stone tools that would have required a level of intelligence and creativity to make. A new analysis, based on the crystals growing inside one of the bones, showed scientists the site dated back to an ice age 146,000 years ago— challenging long-held ideas about early humanity at this site becoming creative thanks to warmer times of plenty. 

“People often imagine creativity as something that flourishes in good times,” says Yuchao Zhao, the assistant curator of East Asian archaeology at the Field Museum in Chicago and the lead author of a paper describing the findings in the Journal of Human Evolution. “Finding out that these stone tools were made during a harsh ice age tells a different story. Hard times can force us to adapt.”

 Zhao and his colleagues, led by senior author Zhangyang Li, a professor at Shandong University in China, have been examining stone tools found at the Lingjing archaeological site in central China. Lingjing was occupied by early humans called Homo juluensis. They were cousins of modern humans (Homo sapiens), and our ancestors may have interacted with them. Homo juluensis show a striking mosaic of features, including very large brain size and traits seen in both eastern Asian archaic humans and Neanderthals in Europe.

Until recently, archaeologists had thought that the ancient humans in East Asia during the late Middle Pleistocene (300,000-120,000 years ago) hadn’t made many significant technological advances, in comparison to the early humans living in Europe and Africa. But the stone tools found at Lingjing tell a different story.

The disc-shaped stone cores at Lingjing might not look especially fancy at first glance, but Zhao and his colleagues’ analysis of them revealed that they were part of a painstaking and carefully organized tool-making process. The Homo juluensis people crafted them by hitting small stones against larger stone cores. 

Some of the cores were worked fairly evenly on both sides. Others were more carefully structured: one side served mainly as the surface to strike from, while the other side was shaped to produce sharp flakes. These asymmetrical cores are especially important because they show that ancient humans were not just knocking pieces off a stone at random. They were managing the core as a three-dimensional object, giving different surfaces different roles and maintaining the right angles to keep producing useful flakes.

“This was not casual flake production, but a technology that required planning, precision, and a deep understanding of stone properties and fracture mechanics,” says Zhao. “The underlying logic of this system— and the cognitive abilities it reflects— shows important similarities to Middle Paleolithic technologies often associated with Neanderthals in Europe and with human ancestors in Africa, suggesting that advanced technological thinking was not limited to western Eurasia.”

So, the stone artifacts left behind by the Homo juluensis at Lingjing suggest that the people there were capable of complex thought and creativity. But the story is further complicated by recent studies that have adjusted scientists’ estimates of how long ago these tools were made.

Lingjing was a site where Homo juluensis came to butcher animals like deer, and these animals’ bones are found alongside the stone tools. One of these bones, a rib from a deer-like animal, contained glittering calcite crystals. Calcite crystals contain trace amounts of uranium, which slowly degrades into another element called thorium. By measuring the ratio of uranium to thorium present in a calcite crystal, scientists can tell how old the crystal is.

“The calcite crystals inside the bone acted like a natural clock, allowing us to refine the age of the site,” says Zhao. 

Previously, researchers thought that the tools found in Lingjing were about 126,000 years old at most, but based on the presence of the crystals, they're about 20,000 years older— a small, but important difference.

“Even though these tools are just a little bit older than we’d previously thought, the entire story is changed,” says Zhao. “During the Pleistocene, Earth repeatedly shifted between colder ice-age periods and warmer intervals between them. We used to think these tools were made 126,000 years ago, during a warm interglacial period, but based on the new dates suggested by the crystals, some of these tools were actually produced 146,000 years ago, during a harsh, cold glacial period.”

The new age assigned to these stone artifacts calls into question the idea that creativity is a luxury for good times; instead, in this case, it seems to be an adaption for surviving hard times.  “Altogether, this research reveals a much richer story of innovation, intelligence, and human evolution in East Asia,” says Zhao.