This 1.4 million year old hand ax was plucked from a hippopotamus

Manual axes are fairly common finds at sites that are between 2 and 1 million years old. These sturdy tools have two sides (also called faces) and a sharp edge on one end. But hand axes are generally made of stone, so archaeologists working at the Konso Formation in southern Ethiopia were surprised to find a hand ax worked from a large chunk of bone buried in a 1 layer of sediment. , 4 million years. When Tohoku University archeologist Katsuhiro Sano and his colleagues compared the bone to a collection of bone samples from large mammals, they discovered that their ancient hand ax had been part of a hippo femur (thigh bone).

From hippopotamus to hand ax

The Konso find is just the second ax that hand ax archeologists have found, and one of the few bone tools from sites over 1 million years old. Based on fossils found in Konso, the hominid that snapped off a piece of hippopotamus and turned it into a nice, sharp hand ax was probably a Homo erectus. Members of the species walked upright and built much like modern humans, eventually spreading from Africa, through Europe and Asia, and into modern Indonesia.

At least one member of this species left behind a 13 cm long hand ax which, according to Sano and his colleagues, is an excellent piece of craftsmanship. The toolmaker apparently detached a large flat piece of bone from the side of a hippopotamus; You can still see the outer surface of the bone on one side of the hatchet. That conforms to Acheulean’s standard approach to making manual axes and other tools; The first step is to make a large “blank” in the correct overall shape, then gradually crumbling smaller pieces to shape the finished product.

For starters, it’s a relatively advanced technique, compared to some previous stone toolmaking styles, because it requires planning and also really good control over what breaks (and how it happens) when you hit one piece of stone with another, to that you can hit. a scale in the size and shape you want. That type of control is even harder to achieve with bone than with stone, and it’s also harder to find bone large enough to make the correct size blanks. Not surprisingly, the only other Acheulean bone hand ax ever found, a 1.3 to 1.6 million year old tool from the Olduvai Gorge in Tanzania, was formed from a piece of elephant bone.

There is no doubt about it: the first hominids were quite sharp

“Fine bone tools such as manual bone shafts are extremely rare,” Sano and colleagues wrote. But Konso’s toolmakers knew what they were about.

The hominid who made the hippo bone hand ax broke the large bone into the correct overall shape, then cut a series of small scales from one end to make a sharp edge. By alternating those flakes from one side to the other, the toolmaker made a remarkably straight 5 cm long cutting edge at the working end of the hand ax.

“This bone ax shows that in Konso, […] H. erectus individuals had sufficient ability to create and use a lasting vanguard, ”Sano and his colleagues wrote. That aligns pretty well with other evidence that H. habilis and H. erectus He understood the material’s properties like sharpness and durability well enough to choose the right material for the right job. Our hominid cousins ​​were already very resourceful, very competent and very intelligent.

In fact, that previous study on the properties of materials raises the question of why this particular hominid chose to make a hippo bone ax, of all things. There would have been many stones available in the area. Actually, Sano and colleagues suggest that the abundance of workable stone around Konso may have helped Acheulean toolmakers hone their craft, as they had plenty of material to work with.

Perhaps they decided to take advantage of a femur hippopotamus that was available on site, or perhaps they faced a temporary shortage of stone; Volcanic activity in East Africa sometimes changed hominid access to stone deposits for centuries at a time. And 1.4 million years ago, the area around Konso would have been a mosaic of wetlands, forests, and grasslands surrounding a large lake, so hippos might have been available to hunters brave enough.

Or maybe the old toolmaker decided that bone was actually the best material for the task at hand.

A practical contraption

The hand ax offers some clues as to what that task might have been. Its 5 cm working edge shows some signs of wear and tear. The edge is rounded in places close to the tip, and under the microscope, Sano and his colleagues noticed patterns of striations and polished patches that resemble the patterns seen in stone tools used to cut animals, work that involves a lot cut and sawn. motions Since that is what most archeologists believe Acheulean hand axes were made for, the explanation makes sense.

Interestingly, one side of the rim looks a little more worn than the other. That may suggest something about how the tool was used or about the user’s dominant hand.

Because bone tools are so rare in the archaeological record of the period just before 1 million years ago, it is difficult to say exactly how significant this finding is or what it tells us. But it is a relic of hominin technology from a very interesting moment: an early phase of the Acheulean style, when toolmaking techniques were rapidly being refined.

“At Konso, this is a period of time when major technological developments in lithic technology were occurring,” the authors wrote. It would have been an interesting time to be a technical critic (but also very frustrating, since you couldn’t write anything).

PNAS, 2020 DOI: 10.1073 / pnas.2006370117 (About DOI).