Studying Lactose Tolerance in Africa (image) University of Pennsylvania Caption Penn's Sarah Tishkoff administers a lactose tolerance test to a group of Maasai people in Tanzania. The test measures the ability to digest milk -- a trait that Tishkoff and other researchers link with the practice of pastoralism. Credit University of Pennsylvania Usage Restrictions In context of reporting Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.