Paleolithic Humans May Have Skill To Discern Rock Properties To Suit Stone Tool Morphologies and Production Techniques

Experts discovered that humans selected rocks for various reasons and not just because of how easy it was to break off. This claim suggests that our ancestors had the technical skill to compare the best rock for their tools.

Technological Innovation During the Paleolithic Era

Stone tools are likely the first cultural artifacts used by historians in reconstructing the world of Paleolithic humans. Stone tools were so significant in this age that the names of the periods are based on the progression of stone tools: Lower Paleolithic, Upper Paleolithic, Mesolithic (Middle Stone Age), and Neolithic (New Stone Age).

As the modern human species moved from Africa to Eurasia, they used stone tools made of rocks, including flint and obsidian, to slice, cut, and craft various weapons. Because of the critical role played by rocks in their culture, archeologists tried to understand the methods used by early humans in making stone tools.

Tool Production Skills of Early Humans

A group of researchers from the Nagoya University Museum and Graduate School of Environmental Studies in Japan has investigated the differences in the physical properties of rocks used by ancient humans during the Paleolithic era.

It was believed that the geographic expansion of Homo sapiens in Eurasia started in the Middle East. Archeologists Seiji Kadowaki and Eiki Suga from Nagoya University explored the prehistoric sites of three chronological periods in the Jebel Qalkha area in southern Jordan. They studied the flint nodules in the outcrops, which were exploited during the Middle and Upper Paleolithic periods.

Kadowaki and Suga believe that Paleolithic humans understood the appropriate rocks for making tools and searched for them intentionally. Their hypothesis suggests that early humans chose translucent and smooth flint since they can be easily broken off the rock face and shaped into sharp edges.

The researchers used a Schmidt Hammer and a Rockwell Hardness Device to analyze the mechanical properties of the rocks. The Schmidt Hammer measures the elastic property of a material, while the Rockwell Hardness Device tests the strength of a rock surface.

As expected, fine-grained flint required less force to break than medium-grained ones. This made the fine-grained flint more attractive in small stone tool production. Indeed, many of the stone tools from the Early Upper Paleolithic era contain fine-grained flint.

However, an earlier study by the same team found that during the Late Middle Paleolithic and Initial Upper Paleolithis period, medium-grained flint was more commonly used in tool production than fine-grained ones. If fine-grained flint was easier to use, why did ancient humans not use them as material for tool making?

Further analysis reveals that much of the fine-grained flint in the area suffered from abundant internal fractures due to geological activities that made it unsuitable for large stone tools. This shows that even if medium-grained flint was a tough material to modify, Paleolithic humans chose them for large tools since they were more likely to last longer.

The result of the study indicates that prehistoric humans had a sensory knowledge of the properties of rocks and intentionally selected the stone material. They also used them according to the form and production technique of the desired stone tools. This intentional selection of the stone raw material may have been an important component of ancient tool production, indicating some elements of flexible technological behavior adapted to the situation.