Christopher Campisano, a co-author of the study and professor from Arizona State University, stated that he and the team saw sharp-edged stone tools sticking out of sediments on a steep, eroded slope. When he peered over the edge of a small cliff, he saw rocks sticking out. He then found two stone tools by scaling up from the bottom of the said cliff and using his rock hammer. (Related: Human evolution may have to be rewritten after scientists discover monkeys can create stone tools like humans.)
Luckily for Campisano and his team, the stone tools were discarded near a water source and were subsequently buried. Vera Aldeias, an archaeologist and researcher from the University of Algarve in Portugal, said that when they looked at the sediments at the dig site under a microscope, they could tell that the site was exposed only for a short period of time. This means that when the stone tools were effectively preserved when they got buried.
Campisano, Aldeias and the other researchers took years of slow, meticulous excavation before they could fully unearth the stone tools. In the process of digging these out, the researchers also came across a layer of bones and hundreds of other stone tool fragments, indicating that there was human activity in the area and that these humans were chipping away at stones in order to make knives.
Early human relatives were using tools long before modern humans even began working with stone. The difference lies in how the BD1 tools were made and used. Stone tools dating back 3.3 million years in Kenya were described as "percussive" stone tools, meaning that they were used for hammering and breaking food. These are known as "Lomekwian" stone tools. The tools discovered in the BD1 dig site are known as "Oldowan" tools, with the main difference being that these tools were chipped to create sharper, more precise edges.
"We expected to see some indication of an evolution from the Lomekwian to these earliest Oldowan tools," said researcher Will Archer. "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."
This suggests that the development of stone tools and tool production went through different stages of progress over the years. David Braun, the lead author of the study, believes that many human ancestors developed their use of stone tools independently of each other in order to extract resources specific to their environment.
"If our hypothesis is correct," Braun said, "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."
He then stated the need to find more dig sites and to do more research. At the very least, their study provides a link between the evolution of human ancestors and the development from Lomekwian to Oldowan tools.