A team of paleontologist recently discovered a set of stone axes that are believed to be the oldest complex tools ever found. At 1.76 million years old, they are some of the oldest examples of human-engineered tech known to exist.

The real shocker is that the type of ax found by the team led by Christopher Lepre of Columbia had previously only been dated to around 1.5 million years ago. That coincides with the rise of Homo erectus (a.k.a. us), who paleoanthropologists believed used the new tech to out-compete other hominins. The newly discovered axes predates the rise of Homo erectus by at least of a quarter of a million years, and were used at the same time as an earlier generation of stone tool tech that’s a million years older.

The axes are part of the Acheulean technology, the oldest class of tools yet discovered that have complex shapes and required advanced (for the time) planning. The prior class, Oldowan tools, are typically knives and axes made from hunks of stone with roughly chipped and shaped edges.

With the discovery of Acheulean axes in the sediment of a Kenyan lake at the same depths as previously-found Oldowan tools, there’s pretty convincing evidence that the rise and fall of the two technologies overlapped for a long period of time in human history. Because Acheulean tools have long been associated with H. erectus and Oldowan tools with the more primitive H. habilis, the discovery offers insight into spread of hominins beyond their African origins.

Paleontologists have figured that most hominin migrations out of Africa were isolated to H. erectus groups. The only fault in that theory was that Eurasian fossil sites rarely had Acheulean tech present, with Oldowan tools being far more popular. With both tool kits being available at similar times, it’s possible that H. erectus was leaving Africa at an intermediate period before Acheulean tools became more widespread. Or, more likely, a number of different hominin species were migrating out of Africa over a period of time, bringing and developing their tookits along the way.

Photo credit: P.-J. Texier, copyright MPK/WTAP