The Oldest Stone Tools Predate Homo Sapiens by Millions of Years

At 3.3 million years old, they predate the next oldest tools by a whopping 700,000 years.

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May 20 2015, 5:00pm

LOM3 stone tool. Image: MPK-WTAP

Scientists have discovered the oldest stone tools ever found, dating back some 3.3 million years to Pliocene Africa—long before the rise of humans' first ancestors in the Homo genus.

The artifacts were found near Lake Turkana, Kenya, and predate the next oldest tools by a whopping 700,000 years. That is an enormous margin, and it will have far-reaching ramifications for our understanding of how material culture initially arose in early hominin communities. An in-depth analysis of the site, its contents, and its significance as a new benchmark in evolutionary history will be published in the May 21 issue of Nature.

Harmand with one of LOM3's tools. Credit: MPK-WTAP

The tools "shed light on an unexpected and previously unknown period of hominin behavior," said archaeologist Sonia Harmand, the lead author of the paper, in a statement. She added that the find "can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone."

Harmand and her colleague Jason Lewis, a co-author on the paper, came across the site by chance on July 9, 2011. The pair had been scouting out the hills surrounding Lake Turkana, which is currently the largest desert lake in the world, but was once a fertile woodland region that supported many hominin communities millions of years ago.

They took a wrong turn at some point and were trying to get back to the main path when came across this rich archeological site, which is now known as Lomekwi 3 (LOM3). According to Harmand and Lewis, the moment that they arrived at the site they "could feel that something was special about this particular place."

The thorough excavation that followed validated the pair's hunch that LOM3 held fascinating archaeological secrets, and 149 tools have since been recovered from the site. The artifacts suggest that these ancient hominins pioneered the knapping techniques involved in artificially shaping stones for specific tasks. The remains of this complex behavior found at LOM3 include anvils, hammers, and cores used to make sharp-edged stones for cutting.

Sammy Lokorodi, a local fossil and artifact hunter, led the way to a trove of 3.3 million-year-old tools. Image: West Turkana Archaeological Project

Harmand recognized that these primitive tools likely set a new record for the world's oldest tools, but it wasn't until she assembled the team of interdisciplinary experts that co-authored this paper that her conclusion was confirmed. Among the specialists who contributed to the study was geologist Chris Lepre, who determined the date of artifacts using a magnetometer.

"The whole site's surprising, it just rewrites the book on a lot of things that we thought were true," said Lepre in a statement.

Indeed, in addition to the startling age of the tools, the larger ecological context of the community that shaped them came as something of a surprise. The advent of tool use is often correlated with climate change in Pliocene Africa, which forced hominin species to capitalize on advancing grasslands instead of clinging to the forested areas to which they were adapted. This is known as the savannah hypothesis, and like so many hypotheses related to human evolutionary biology, it is controversial.

To that point, the Nature study seems to suggest that the invention of tools is not inherently related to a savannah environment. The enterprising ancient hominins that made these items lived in a wooded, shrubby kind of environment, and accordingly, they may have used their tools for different purposes than the grassland species that emerged 700,000 years later.

The LOM3 site. Image: MPK-WTAP

It seems likely that they were bashing apart tubers and nuts with their specially fashioned rocks, but maybe they were also using them to extract grubs from rotten logs and dead trees. The fact is, we don't know, and it will take a lot more research to figure out the finer details.

As Lepre noted in a statement, "When you [figure out] these things, you don't solve anything, you just open up new questions. I get excited, then realize there's a lot more work to do."