The new discoveries at Olorgesailie push things back even further. They suggest that many of our most important qualities—long-term planning, long-distance exploration, large social networks, symbolic representation, and innovative technology—were already in place 20,000 to 40,000 years earlier than believed. That coincides with the age of the earliest known human fossils, recently found elsewhere in Africa. “What we’re seeing in Olorgesailie is right at the root of Homo sapiens,” Potts says. “It seems that this package of cognitive and social behaviors were there from the outset.”

“They demonstrate human ways of thinking and doing that cannot be traced easily in the remains of our skeletons or genes,” says Marlize Lombard, an archeologist at the University of Johannesburg. “They provide strong indicators that by about 300,000 years ago we were well on our way to become modern humans in Africa.”

It’s a “textbook example of good archaeological practice,” adds Lyn Wadley from the University of Witwatersrand.

For the longest time, most of the tools that were uncovered at Olorgesailie were Acheulean handaxes—large, teardrop-shaped tools made by chipping away at cores of stone. Hominids like Homo erectus used these implements to butcher meat and cut wood. At Olorgesailie, they started doing this 1.2 million years ago, and continued until at least 500,000 years ago. And during all that time, the basic design of the axes changed very little. In an age where the phones in our pockets can become obsolete in a year, “the idea of a single technology lasting that long is almost inconceivable,” says Potts.

Acheulean hand axes did eventually go obsolete, giving way to the tools of the Middle Stone Age. These were smaller, more carefully shaped, more specialized, and more varied. Instead of just bulky axes and cleavers, they also included spear tips, scrapers, and awls. Potts’ team started finding these at Olorgesailie in the early 2000s, and Alan Deino from the Berkeley Geochronology Center worked out how old they are by analyzing levels of radioactive isotopes of argon and uranium in the samples. He concluded that these tools had completely replaced the Acheulean designs by at least 305,000 years ago.

Many of the tools were made from a black volcanic rock called obsidian, which was brought to the site and processed there. But from where? There aren’t any obsidian outcrops near Olorgesailie. The chemistry of the tools suggests that they came from sources up to 100 kilometers away. But “these are straight-line distances that, in some cases, go over the top of a mountain,” says Alison Brooks from George Washington University.

It’s unlikely that the residents of Olorgesailie regularly commuted to get their obsidian. Instead, they probably took part in long-distance trade networks, receiving obsidian from people who lived in distant locales presumably in exchange for other goods. “There’s an occasional piece in the Acheulean that gets transported these distances,” says Brooks. “But we have thousands of pieces in this one site that’s smaller than most people’s kitchens. There has been a really major import of raw materials.” If she’s right, then Olorgesailie’s obsidian network precedes other examples of long-distance trade by 80,000 to 100,000 years.