Hunter-gatherers heated lake gunk to make ochre paint

This is a sample of rock art found at Babine Lake. It is representative of the rock art that was analyzed in the study. (Credit: U. Missouri)

Researchers have figured out how ancient hunter-gatherers in North America created ochre paint to produce rock art located at Babine Lake in British Columbia.

Ancient artists often used ochre, one of Earth’s oldest naturally occurring materials, as a vivid red paint in rock art known as pictographs across the world. Despite its broad use throughout human history and a modern focus on interpretations of the artistic symbolism, little research exists on the paint itself and how ancient people produced it.

“Ochre is one of the only types of material that people have continually used for over 200,000 years, if not longer,” says Brandi MacDonald, an assistant research professor in the Archaeometry Laboratory at the University of Missouri Research Reactor (MURR) with a joint appointment in the anthropology department. MacDonald specializes in ancient pigments.

“Therefore, we have a deep history in the archeological record of humans selecting and engaging with this material, but few people study how it’s actually made.”

A rock wall is covered in red and orange paint, with different lines and shapes overlapping
Another sample of rock art at Babine Lake, representative of the rock art that researchers analyzed. (Credit: U. Missouri)

This is the first study of the rock art at Babine Lake. It shows that individuals who prepared the ochre paints harvested an aquatic, iron-rich bacteria out of the lake—in the form of an orange-brown sediment.

In the study, the scientists used modern technology, including the ability to heat a single grain of ochre and watch the effects of temperature change under an electron microscope. They determined that individuals at Babine Lake deliberately heated this bacteria to a temperature range of approximately 750°C to 850°C to initiate the color transformation.

“It’s common to think about the production of red paint as people collecting red rocks and crushing them up,” MacDonald says. “Here, with the help of multiple scientific methods, we were able to reconstruct the approximate temperature at which the people at Babine Lake were deliberately heating this biogenic paint over open-hearth fires. So, this wasn’t a transformation done by chance with nature.

“Today, engineers are spending a lot of money trying to determine how to produce highly thermo-stable paints for ceramic manufacturing or aerospace engineering without much known success, yet we’ve found that hunter-gatherers had already discovered a successful way to do this long ago.”

The study appears in Scientific Reports. The authors would like to acknowledge the permission and support of the descendant Lake Babine Nation, upon whose traditional territory the rock art resides.

Additional coauthors are from the University of Missouri, the Bigelow Laboratory for Ocean Sciences, the University of Arizona, the University of Northern British Columbia, the Brockhouse Institute for Materials Research.

Funding came from the National Science Foundation, NASA, the Office of Naval Research, and the University of Missouri. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

Source: University of Missouri