Stone Age herders transported heavy rock tools to grind animal bones, plants and pigment

About 7,000 years ago, a small group of people sat around a fire, next to a small lake in what is now the Nefud Desert of northern Saudi Arabia. We found some of the tools they left behind – and on close inspection of the tools, we discovered these Stone Age herders were busy grinding animal bones, wild plants and pigments while their meat was cooking. Our results are published in a new paper in PLOS ONE.

Herders and artists

• Herders lived around these lakes and led their cattle, sheep and goats to the best pastures.
• These Stone Age herders were also skilled artists.

Stone Age camp sites

• Archaeological sites from this period consist of collections of small fireplaces.
• The herders seem to have been extremely mobile, moving around the landscape with their herds, searching for pasture and water.
• There are no plant remains in the archaeological sites, and animal bones only survive in small fragments.
• So, we turned to microscopic analysis in order to help determine the function of the grinding tools.

Microscopic traces

• In experiments we find that grinding different materials, such as bone, pigment, or plants, leaves distinctive microscopic marks on the surface of the grinding tools.
• These marks, including striations, fractures, rounding of individual quartz grains and different types of polish, can be seen with a microscope.
• We looked at the Stone Age grinding tools to identify similar traces, and from them to determine what materials were ground.
• Our microscopic study showed the grindstones were used for a range of different purposes.

Valuable tools

• Our analysis of the grinding marks also showed the tools were often used for different materials over time.
• They were clearly valuable and used as much as possible.
• We’re still not sure why the discarded tools were placed on the fire – perhaps they used them to cook or to dry their meat.