The latest discovery of the world’s oldest stone tool could be a game changer for scientists trying to piece together a clearer picture of human evolution. For one, the stone tool is 700,000 years older than the previously known date of such tools, shaking up previously held ideas on human evolution. The study, published in the journal Nature, suggests that our most direct ancestors may not have been the first to create stone tools.
Researchers came across the stone tool almost by accident after travelling onto the wrong path during their expedition. After fanning out and surveying the area, they found 149 artefacts that related to tool making. The objects ranged from stone cores and flakes to rocks used for hammering and possibly even as anvils.
Lead author Sonia Harmand says in a statement that the discovery unravels crucial details of “an unexpected and previously unknown period of hominin behavior and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone.”
Tool making was initially associated with the genus Homo, an ancestral line that leads directly to Homo sapiens. Instead, this study suggests that an earlier group of Hominins – the clade that includes modern humans – could have been exploiting this technology. Researchers wrote down that they "could feel that something was special about this particular place."
To figure out how old the stone tool was, they first analyzed the layer of volcanic ash found below the tool site. By investigating magnetic minerals found around the tools, researchers were then able to confirm the site dated back to 3.11 million to 3.33 million years.
"The capabilities of our ancestors and the environmental forces leading to early stone technology are a great scientific mystery," said Richard Potts, director of the Human Origins Program at the Smithsonian National Museum of Natural History, who was not involved in the research, in a statement.
"Researchers have thought there must be some way of flaking stone that preceded the simplest tools known until now. Harmand's team shows us just what this even simpler altering of rocks looked like before technology became a fundamental part of early human behavior," he added.
After studying the carbon isotopes in the soil, researchers were able to reconstruct the environment and were surprised to find that – at the time – the site was shrubby and partially wooded. This challenges previous notions that tool making evolved in response to a change in climate, which led to the development of broad savannah grasslands.
The question of who made and used the tool still remains a mystery. Researchers suggest that the skull of a 3.3-million-year-old hominin, Kenyanthropus platyops, which was found a mile from the site in 1999, could be the key to solving the puzzle. Alternatively, the tools could have been made by another species from the same era.