Red ochre and shells: clues to human evolution.
The 200-kiloannus (ka) use of red ochre and shells by humans is interpreted as a simple clue of symbolic thinking. Integration of multiple lines of evidence supports the opinion that the use of red ochre and shells might have had direct significance for human evolution. Use of seafood and red ochre supplies docosahexaenoic acid (DHA), possibly iron, and other essential nutrients for brain development and reproductive health, improving human fitness and triggering brain growth. The fitness advantages to humans of using shells, and possibly red ochre, might have selected for artistic and symbolic expression, and, thereby, lead to social cohesion. Current global health syndromes show that an adequate supply of seafood and iron continues to play a fundamental role in human health.