Ancient Stone Toolmaking Evolved Multiple Times Across Continents

Technological evolution and variability at Nor Geghi 1. (A) bifaces, (B) Levallois cores / Daniel S. Adler
Janet Fang 26 Sep 2014, 00:57

In the last few decades, archaeologists thought that a stone age technology called Levallois was invented in Africa before it spread elsewhere. Now, a discovery of thousands of artifacts suggests that the technology evolved independently in different populations in Eurasia also. The work, published in Science this week, describes the earliest use of Levallois technology in Europe and Asia -- challenging ideas that the innovation came from a single origin and spread after the early human exodus from Africa.

Levallois technology involves using a hammer-type tool to strike at the convex surface of a large stone, called a lithic core. This causes smaller flakes to detach, and these are then retouched into a variety of tools like blades, points, or hide scrapers. Whatever is left of the lithic core (now with sharpened edges) can be further trimmed into a knife. These appeared in the record across Eurasia 200,000 to 300,000 years ago, and earlier in Africa. Before this, early humans used the simpler bifacial technology, where a stone is shaped into a hand axe by chipping flakes from two surfaces; these flakes are discarded afterwards. The development of Levallois, and the disappearance of bifaces, was used to mark the transition from the Lower to the Middle Paleolithic, roughly 300,000 years ago. But now we may need to rethink this. 

An international team led by Daniel Adler from University of Connecticut examined thousands of tools, varying greatly in style, excavated from the Nor Geghi 1 sedimentary bed (pictured below) in Armenia’s Southern Caucasus region. Preserved between two lava flows dated 200,000 and 400,000 years old, this was an important dispersal corridor for our extinct ancestors moving out of Africa.

Here, they found a location where bifacial and Levallois technology were used at the same time. “The combination of these different technologies in one place suggests to us that, about 325,000 years ago, people at the site were innovative," Adler says in a news release. The varied artifacts reflect the technological flexibility and variability of a single population -- rather than chronologically distinct groups or multiple groups with distinct toolmaking traditions overlapping the same space. Below is a sampling from Nor Geghi 1: biface with two biface resharpening/thinning flake byproducts (A), Levallois cores with Levallois flakes (B,C), blade core with blade (D). 

With Levallois, detached flakes of predetermined size and shape are the desired products, while the flakes detached during the making of bifaces are treated as waste. Comparisons across Africa, the Middle East, and Europe show that the evolution of Levallois was gradual and intermittent, occurring independently in populations sharing a common technological ancestry. That is, Levallois technology evolved out of pre-existing biface technology in different places at different times. 

“We wouldn’t have found this mixture if the Levallois technology had simply replaced the old method,” Adler tells Nature. “The communities probably worked out for themselves how to make bifacial tools and then it was a short step to the Levallois method.” The latter was more economical, making optimal use of raw material -- plus the small predetermined flakes are easy to carry. Furthermore, chemical analyses show that early humans used obsidian outcrops 120 kilometers away, suggesting they were capable of exploiting environmentally diverse territories.

Images: Daniel S. Adler

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