This 1.4 million-year-old hand axe was chipped off a hippo femur

Enlarge (credit: By Diego Delso, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=74486418)

Hand axes are fairly common finds at sites dating between 2 million and 1 million years old. These sturdy tools have two sides (also called faces) and a sharp edge at one end. But hand axes are usually made of stone, so archaeologists working at the Konso Formation in southern Ethiopia were surprised to find a hand axe worked from a large chunk of bone buried in a 1.4 million-year-old layer of sediment. When Tohoku University archaeologist Katsuhiro Sano and his colleagues compared the bone to a collection of bone samples from large mammals, they found that their ancient hand axe had once been part of a hippopotamus femur (thigh bone).

From hippopotamus to hand axe

The Konso find is only the second bone hand axe archaeologists have ever found, and one of just a handful of bone tools from sites older than 1 million years. Based on fossils found at Konso, the hominin who flaked off a chunk of hippo femur and worked it into a nice, sharp hand axe was probably a Homo erectus. Members of the species walked upright and were built a lot like modern humans, and they eventually spread from Africa, across Europe and Asia, and all the way to modern Indonesia.

At least one member of this species left behind a 13cm-long hand axe that is, according to Sano and his colleagues, an excellent piece of craftsmanship. The toolmaker apparently flaked a large, flattish piece of bone off the side of a hippo femur; you can still see the outer surface of the bone on one side of the hand axe. That fits the standard Acheulean approach to making hand axes and other tools; the first step is to make a large blank" in the right general shape, then gradually flake off smaller pieces to shape the finished product.

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