Stone tools uncovered at an archaeological site in central China may have been made during a severe Ice Age, according to new research that reshapes ideas about early human innovation.
The study, published in the Journal of Human Evolution, examined crystals that formed inside an ancient animal bone found at the Lingjing site. Researchers used the crystals to date the site to around 146,000 years ago — roughly 20,000 years earlier than previous estimates.
That difference matters because it places the tools in a cold glacial period rather than a warmer phase of the Ice Age.
“For a long time, people linked technological advances with stable and favourable conditions,” said Yuchao Zhao of the Field Museum in Chicago, lead author of the study. “But these tools appear to have been made during a much colder climate.”
Lingjing has been studied for more than a decade and is linked to Homo juluensis, an extinct human relative that lived in East Asia during the Middle Pleistocene. The site contains animal bones alongside stone artefacts believed to have been used for butchering.
At first glance, the tools seem fairly simple. Closer analysis showed something more deliberate. The stone cores were shaped in a controlled way to produce sharp flakes, and some were worked differently on each side depending on their purpose.
Researchers say this points to careful planning rather than random strikes.
“These people understood how stone would break and how to keep producing useful cutting edges,” Zhao said.
The team compared some of the methods used at Lingjing with Middle Palaeolithic tool-making traditions associated with Neanderthals in Europe and early human groups in Africa.
The revised age of the site comes from calcite crystals found inside the rib bone of a deer-like animal. Because uranium inside the crystals slowly changes into thorium over time, scientists can use the ratio between the two elements to estimate age.
“The crystals acted almost like a timestamp inside the bone,” Zhao said.
Previous estimates dated the tools to around 126,000 years ago. The new evidence suggests they were made during a colder and more difficult period.
Researchers argue that this changes the broader picture of human development in the region. Instead of innovation appearing mainly during times of abundance, the evidence from Lingjing suggests that harsh conditions may also have pushed ancient humans to develop new techniques and adapt their behaviour.
Header Image Credit : Yuchao Zhao
Sources : Field Museum
