Anthropologists often use ochre processing as a proxy for the origins of human symbolic thought. That’s partly because ochre is relatively difficult to make, requiring a few steps and at least two kinds of tools. As the researchers write, ochre comes from “rocks containing a high proportion of iron oxides, often mixed with silicates and other mineral substances, which are red or yellow in color, or are streaked with such shades.” Ochre itself is made by pulverizing the rock with one kind of tool and then reducing it to a powder between two grindstones.
There are many aesthetic uses for ochre, including as fabric dye, paint for cave walls, or a stain for rocks and other materials. All these artistic or cosmetic uses imply symbolic thought. But early humans used ochre for utilitarian purposes, too. The powder was mixed with other adhesives to keep weapons snugly attached to their hafts. Put simply, ochre was a key ingredient in glue.
The question that has long raged among archaeologists is whether people first began using ochre as a tool for engineering or as a substance for making art. In other words, does symbolism start with science or aesthetics? By examining 23 ochre-processing tools from Porc-Epic Cave, researchers figured out that the answer is that both emerged at the same time, in the same workshops.
A fascinating article, the full story is here.