Chapter 39, Problem 1DAA

Human Adaptation to a Starchy Diet The human AMY-1 gene encodes salivary amylase, an enzyme that breaks down starch. The number of copies of this gene varies, and people who have more copies generally make more enzyme. In addition, the average number of AMY-1 copies differs among cultural groups.

George Perry and his colleagues hypothesized that duplications of the AMY-1 gene would be selectively advantageous in cultures in which starch is a large part of the diet. To test this hypothesis, the scientists compared the number of copies of the AMY-1 gene among members of seven cultural groups that differed in their traditional diets. FIGURE 39.16 shows their results.

FIGURE 39.16 Number of copies of the AMY-1 gene among members of cultures with traditional high-starch or low-starch diets. The Hadza, Biaka, Mbuti, and Datog are tribes in Africa. The Yakut live in Siberia.

1. Starchy tubers are a mainstay of Hadza hunter–gatherers in Africa, whereas fishing sustains Siberia's Yakut. Almost 60 percent of Yakut had fewer than 5 copies of the AMY1 gene. What percentage of the Hadza had fewer than 5 copies?