Thursday, 30 October 2014

Acheulian and Levallois technologies from a single Late Pleistocene site Armenia.

Stone tools associated with the Acheulian technology first appeared around 1.75 million years ago and spread across much of Eurasia from about 900 000 years ago onwards. The technology is typified by tools in which pieces are chipped away from a central core to leave a useable item such as a handaxe. The Levallois technology appeared in Africa around 300 000 years ago and spread across Eurasia by about 200 000 years ago. In Levallois technology the chips derived from a central core are themselves used as cutting tools, which the core is retained as a source of material rather than being used as a tool in itself, enabling a larger number of tools to be fashioned from a single piece of usable rock. This is thought to be a major conceptual shift, and is associated with the appearance of Early Modern Humans in Africa and Neanderthals in Europe. In technical terms the Archeulian technology is considered to be Early Palaeolithic while the Levallois is Middle Palaeolithic.

In a paper published in the journal Science on 26 September 2014, a team of scientists led by Daniel Adler of the Department of Anthropology at the University of Connecticut describe a site in Armenia at where obsidian tools belonging to both the Acheulian and Levallois technologies have been found.

The Nor Geghi site was discovered in 2008 in Hrazdan Gorge on the edge of the Armenian Volcanic Highlands. At the site obsidian (glassy volcanic rock) tools were found to be being eroded from a 135 m section on the west side the side of the gorge. The rocks here comprise sedimentary rocks interbedded with basalt lava flows derived from the Hatis, Gutanasar, and Mensakar volcanoes in the Gegham Range. These basalts are amenable to isotope dating methods, with the layer above the stone tools dated to 197 000 years ago, while the layer below is dated to 441 000 years ago, while an unconformity located below the stone tools produced sand grains dated to 308 000 years ago, suggesting the tools were deposited between 197 000 and 308 000 years ago (an unconformity represents a period when sediments were being eroded rather than deposited, sedimentary sequences associated with rivers typically contain many unconformities, as the river shifts is course and erodes where it had once deposited).

The Acheulian and Levallois tools at Nor Geghi appear to be eroded from a single plane, implying that they were made at the same time, and presumably by the same people (the alternative theory, that two different groups were living in the area and both visiting the site to make tools is rejected, since all human groups likely to have been in the area at the time are thought to have been intelligent enough to adopt a better technology if they saw it being used).  This implies that the tool-makers were in the process of switching from one technology to the other when occupying the site. This is significant, as it is currently widely believed that the Levallois technology was developed in Africa and then spread to Eurasia, replacing the earlier Acheulian technology. At Nor Geghi a transitional stage is for the first time recorded outside of Africa, suggesting that the development of a the new technology was not confined to a single place, but developed independently from the old technology across the Old World.

Obsidian artifacts from Nor Geghi.Levallois: (1 and 2) recurrent cores; (3, 11, 13 to 15 and 17) flakes; (4) point with retouched base; (5 to 8) blades; (9 and 10) preferential cores. Non-Levallois: (12) scraper with Quina retouch; (16)biface. Adler et al. (2014).

See also…

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