Scientists have unveiled an extraordinary new analysis of thousands of stone tools found at a site called Attirampakkam in India, northwest of Chennai in Tamil Nadu. Thanks to new dating techniques, a team led by archaeologist Shanti Pappu determined that most of the tools are between 385,000 and 172,000 years old. What makes these dates noteworthy is that they upend the idea that tool-making was transformed in India after an influx of modern Homo sapiens came from Africa starting about 130,000 years ago.
According to these findings, hominins in India were making tools that looked an awful lot like what people were making in Africa almost 250,000 years before they encountered modern humans. This is yet another piece of evidence that the “out of Africa” process was a lot messier and more complex than previously thought.
Pappu worked out of the Sharma Centre for Heritage Education in Chennai with a team of geoscientists and physicists to date the tools. They used a technique called “post-infrared infrared-stimulated luminescence,” which measures how long ago minerals were exposed to light or heat. In essence, it allows scientists to determine how long ago a tool was buried and hidden from the Sun’s heat, and it uses that information as a proxy for the tool’s age.
Writing in Nature, the group explains that the Attirampakkam site is ideal for this kind of dating, because it was regularly flooded by a nearby stream, meaning that discarded tools were quickly covered up by sediments in the water. Those regular floods left behind a relatively tidy stack of debris layers, each of which could be dated.
To their surprise, Pappu and her colleagues found that this region—once a tree-shaded shoreline, ideal for long-term camping—had been occupied by early humans for hundreds of thousands of years. Partly that’s because the river carried great heaps of quartzite rocks and pebbles to the area. Quartz was the preferred stone for tools, and it’s obvious that this place was a tool workshop. Alongside axes, knives, projectile points, and scrapers, the team found half-finished tools and discarded flakes created by chipping away at a rock to make a blade.