The apolipoprotein E (ApoE) gene and its related protein help to mediate cholesterol metabolism and the transporting of fatty acids to the brain. People in our industrialized society with an ApoE4 variant have up to four times the risk of developing Alzheimer’s and other cognitive declines. Researchers at Arizona State University’s School of Human Evolution and Social Change and ASU’s Center for Evolution and Medicine examined how this gene variant might function differently in a more primitive environment. They examined a population of Amazonian forager-horticulturalists called the Tsimane, who have high exposure to parasites and pathogens. They expected the subjects would have a faster and more severe mental decline, but found that those individuals who carried the ApoE4 variant and had a high parasitic burden displayed more stable or improved cognitive function versus non-carriers with a similar level of parasitic exposure.