There are individuals who maintain the ability to digest milk into adulthood due to a genetic adaptation in populations that have a history of pastoralism. Sarah Tishkoff from the University of Pennsylvania presents her latest studies of the genetic basis of lactose tolerance in African pastoralist populations. Her team has identified several mutations that arose independently in East African pastoralist populations. This demonstrates a striking footprint of natural selection in the genomes of individuals with these mutations. It shows that the age of the mutations associated with lactose tolerance in Europeans and Africans is correlated with the archeological evidence for origins of cattle domestication. Thus, the genetic adaption for lactose tolerance is an excellent example of gene-culture co-evolution. Part of the series of CARTA: Center for Academic Research and Training in Anthropogeny.