A rare bone hand axe made by Homo erectus has been discovered in Ethiopia. The tool was unearthed in the Konso Formation of southern Ethiopia in a sedimentary layer dating to the early Acheulean era around 1.4 million years ago. Comparison of the bone to other samples identified it as coming from the femur of a hippopotamus.

The team has discovered other Homo erectus hand axes at the site, but they are all made of stone. Only one other bone hand axe made by Homo erectus in this period has ever been found before. It was discovered in the Olduvai Gorge in Tanzania and was made of elephant bone.

The hand axe is five inches long and was expertly flaked and chipped to create a sharp, straight cutting edge. This is difficult enough to accomplish with stone, requiring precision and understanding of how it will break. The difficulty level increases exponentially with bone as it doesn’t sheer off as predictably as flint, say. You also need a blank of significant size, a large chunk of bone from a large animal.

The hippo hand axe shows evidence of use. The edge near the tip has rounded and there are microflake scars, wear polish and striations. The striations are mostly oblique along the edge indicating the tool was used in the lengthwise motions of cutting/sawing typical of butchering.

Along with a variety of stone tools now recognized at several East African sites, the bone hand ax “suggests that Homo erectus technology was more sophisticated and versatile than we had thought,” [University of Tokyo researcher Gen] Suwa says. Taken together, these finds show that, perhaps several hundred thousand years earlier than previously known, the H. erectus toolkit consisted of items requiring a series of precise operations to manufacture, such as stone and bone hand axes, as well as simpler tools that could be made relatively quickly.