Woman rolling her tongue.
© Science Museum / Science & Society Picture Library
Close-up of mouth. In 1940 the American genetic scientist Alfred Henry Sturtevant (1891-1970) published a paper claiming that tongue-rolling was a genetic trait. Sturtevant concluded that people who inherited the dominant tongue-rolling gene, or allele, (coded 'R') from at least one of their parents could roll their tongues, but that people who inherited a recesive or mutated form of this allele gene (coded 'r') from both parents, could not. He later admitted that tongue-rolling was not simply genetic but subject to environmental factors, and could be learned.