Stone tools from Kenya give early glimpse of human behavior

Stone tools and other items from ancient sites in Kenya give a glimpse at the emergence of some key human behaviours, perhaps including a building of relationships with distant neighbours, new research says. Scientists can’t be sure whether the objects were made by our species, Homo sapiens, or some close relative that’s now extinct.

But at about 320,000 years old, they’re roughly the same age or a bit older than the earliest known H. sapiens fossils, which appeared in Morocco. In any case, they show “foundations of the origin of modern human behaviour,” says Richard Potts of the Smithsonian Institution, one of the researchers reporting the find in three papers released on March 15 by the journal Science. The tools are much smaller and more sophisticated than the older, teardrop-shaped stone tools found in the same area in southern Kenya. Some were made of a volcanic rock, obsidian, that didn’t come from the area, meaning the toolmakers travelled miles to get it. And those excursions must have led them to encounter groups of H. sapiens or our close evolutionary relatives.

The toolmakers likely made connections with them so that they wouldn’t be threatened when they showed up on somebody else’s turf, the researchers said. “I don’t think you would last very long if you went around grabbing someone else’s obsidian without their permission,” said Alison Brooks, an anthropology professor at George Washington University in Washington, DC, and another author of the papers. Potts stressed that the researchers don’t claim that they’ve identified the birthplace of this tool style, but rather that the finds represent what was going on in at least one part of Africa. The older stone tools are from 1.2 million to about 500,000 years ago. Then, because of the geology of the sites, nothing is preserved until 320,000 years ago, when “we have a total replacement” of the old tool style by a more advanced one, Potts said.

Analysis showed much of the obsidian was from places about 15 miles to 30 miles (25 to 50 kilometres) away in five different directions. So that means the toolmakers maintained mental maps of where to go find it, Potts said. The volcanic rock was brought in as a raw material and then turned into the sharp-edged chips. The rock was evidently valuable, and so it might have been traded, Potts said. He also said the toolmakers may have been spurred to create a wide-ranging social network as a hedge against the unpredictability of water and food supplies, caused by shifts in the natural environment. “Networks are the way that hunter-gatherers protect themselves against disaster in the future,” said Brooks.