These Stone Tools Made 2.6 Million Years Are the Oldest of Their Kind

excavated stone tools
Left: A large green artifact found in situ at the Bokol Dora site. Right: Image of the same artifact and a 3D model of the same artifact. David R. Braun

An international team of researchers say they have uncovered the earliest evidence of systematic flaked stone tool production and use at a site in Ethiopia.

Previously, scientists had evidence for the production of flaked stone tools made by hominins—the large group of primates which includes all human species—dating back 3.3 million years. This predates the emergence of our genus—or group of species—called "homo."

However, the earliest known evidence for the "systematic production" of such tools extended back only 2.58 to 2.55 million years ago to Gona in Ethiopia—what is described as "Oldowan technology."

But according to a study published in the Proceedings of the National Academy of Sciences, the researchers, led by David Braun from George Washington University, have discovered another Oldowan site known as Bokol Dora 1 (BD 1) which extends the history of systematic tool-making further back to around 2.61 million years ago.

The researchers say that while the stone tools they found showed similarities to those at other Oldowan sites, they are, in fact, more primitive. Nevertheless, they are also technologically distinct from the earliest tools made around 3.3 million yeas ago that are attributed to early hominins—known as "Lomekwian" technology—as well as those used by modern primates.

"We expected to see some indication of an evolution from the Lomekwian to these earliest Oldowan tools," Will Archer, another author of the study from the Max Planck Institute for Evolutionary Anthropology, said in a statement. "Yet when we looked closely at the patterns, there was very little connection to what is known from older archaeological sites or to the tools modern primates are making."

The team say the stone tools at BD 1 were likely preserved for so long because they were buried close to a water source.

"Looking at the sediments under a microscope, we could see that the site was exposed only for a very short time," Vera Aldeias, an author of the study from the University of Algarve, Portugal, said in a statement. "These tools were dropped by early humans at the edge of a water source and then quickly buried. The site then stayed that way for millions of years."

The stone tools were found close to Ledi-Geraru in northeastern Ethiopia where the oldest fossil attributed to the homo genus was uncovered in 2013. These bones were dated to around 2.78 million years ago, about 200,000 years before the oldest Oldowan stone tools.

It is still unclear whether there is any link between the origins of our genus and the origins of systematic stone tool manufacture. Improved tool production technology may have allowed our ancestors to expand the kinds of food that they ate, at a time when rapid environmental changes were taking place in the east Africa. This could have had an effect on the evolution of homo individuals through selective pressures.

According to the researchers, the differences between the technology that they found and the the stone tools discovered 3.3 million years ago indicates that the production of such objects was invented on multiple separate occasions.

"Given that primate species throughout the world routinely use stone hammers to forage for new resources, it seems very possible that throughout Africa many different human ancestors found new ways of using stone artifacts to extract resources from their environment," Braun said in a statement.

"If our hypothesis is correct then we would expect to find some type of continuity in artifact form after 2.6 million years ago, but not prior to this time period. We need to find more sites," he said.