Diet has played a major role in the evolution of human and non-human primate digestive systems. Phytanic acid is a potentially toxic branched chain fatty acid that can be acquired in humans by ingesting plant and/or animal products. Although it was established that humans cannot derive phytanic acid from chlorophyll and instead normally obtain it only from meat, dairy, and fish products, less was known about the capacity of non-human primates with proportionally larger hindguts to obtain phytanic acid from plant materials. University of Southern California professor Joseph Hacia discusses studies profiling phytanic acid levels in red blood cells obtained from humans and captive non-human primates all on low phytanic acid diets. (#37379)