In an excavation site in Ethiopia, archaeologists unearthed a collection of 327 stone tools created by prehistoric humans more than 2.58 million years ago.

Prior to this discovery, the oldest known example of stone tools was believed to be about 2.56 to 2.58 million years old.

According to a recently published study led by Arizona State University and George Washington University, the collection of stone tools suggests that stone tools were invented many times before they spread across the continent and became an integral part of the everyday lives of early humans.

Details of the discovery appears in the Proceedings of the National Academy of Sciences.

Oldest Stone Tools Ever Found

The excavation site where the collection was unearthed is close to where archaeologists found the oldest fossil attributed to the genus Homo. This fossil was dated to about 2.78 million years ago. Researchers spent five years trying to figure out if there is a connection between the origins of the Homo genus and systematic stone tool production.

The researchers had a breakthrough when Chris Campisano, a geologist and one of the authors of the study, spotted sharp-edged stone tools sticking out of a steep, eroded slope.

"At first we found several artifacts lying on the surface, but we didn't know what sediments they were coming from," recalled Campisano. "But when I peered over the edge of a small cliff, I saw rocks sticking out from the mudstone face. I scaled up from the bottom using my rock hammer and found two nice stone tools starting to weather out."

It took several years to excavate through the sediment and uncover hundreds of chipped stones, now the oldest evidence of human ancestors using knives. The researchers explained that the artifacts were preserved because they were buried close to a water source.

The team dated the volcanic ash several meters below the site and found pieces of evidence of "normal" magnetic polarity. The reversal from "normal" to "reverse" happened 2.58 million years ago, which means that the recently unearthed stone tools were created way before the shift.

From Lomekwian To Oldowan

The newly unearthed stone tools, ascribed to the Oldowan technology, are significantly different from the Lomekwian technology attributed to early hominins and modern primates. The oldest Lomekwian tool found was dated to about 3.3. million years ago.

About 2.6 million years ago, stone tool production shifted from Lomekwian to Oldowan.

"We expected to see some indication of an evolution from the Lomekwian to these earliest Oldowan tools," said Will Archer from the Max Planck Institute for Evolutionary Anthropology and one of the authors of the study. "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."

The shift in toolmaking happened around the same time the teeth of human ancestors also began to change.

The lack of a clear connection between the earlier stone tools means that tools were invented multiple times by many different human ancestors.