Bones to shape stones

One of the great mysteries of prehistory is to understand the process of behavioural evolution in hominid groups. The main area of research has understandably concentrated  on lithic technologies, but other types of artefacts can help illuminate this process.

Recent research led by Ruth Blasco of the Gibraltar Museum, examined two bone retouchers (for retouching stone tools) dated to between the second half of the Middle Pleistocene and the beginning of the Upper Pleistocene – between 100.000 and 350.000 years BP. One originates from Bolomor Cave (Spain) and the other from Qesem Cave (Israel).

The emergence of these tools is found in the latest phases of the Acheulean and their use seems to coincide with widespread and emerging cultural complexes at both ends of the Mediterranean Sea: the pre-Mousterian of Western Europe and the Acheulo Yabrudian of the Levant. Collectively viewed, these retouchers represent significant behavioural changes seemingly taking place between 400 and 300 thousand years ago in two entirely separate parts of the world.

A fresh bone

Previous analyses of retouchers had only ever provided contradictory results regarding a potential selection criteria for use, but experimental work indicated that an important factor was the relative freshness of the bone. It was also noted that the tool maker would have to remove the periosteum (a membrane that covers the outer surface of all bones) as it would otherwise interfere with the flaking process. These attributes are evident on the two bones examined, although it is difficult to evaluate the precise state at the time of use, the retoucher from Bolomor seems to correspond to a fresh, defatted bone, the elasticity of which was still intact. The bone retoucher from Qesem Cave displays a slight increase of pits and scores, which is consistent with a semi-fresh bone.

Innovators

The bone retouchers from the two caves represent some of the earliest examples known to date and both possess typical morphological and functional characteristics of such tools, despite the distance between sites. The researchers can only surmise that the similar technological advancement indicates convergent developments.

Both of these cultural groups were innovators, creating a new series of behaviours, including the use of fire on a regular basis, the roasting of meat (suggested by the presence of large amounts of burnt bones), and lithic recycling .

By using bone tools to alter other raw materials and thus connect different materials in new ways is not merely a technological innovation but an innovative human behaviour. By using bones that originated in hunted, defleshed and consumed animals into the lithic production process, it brings together two basic elements of prehistoric life – stone tool making and animal hunting/consumption.
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References:

Past Horizons. 2013. “Bones to shape stones”. Past Horizons. Posted: October 16, 2013. Available online: http://www.pasthorizonspr.com/index.php/archives/10/2013/bones-to-shape-stones