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 39.9 shows their results.

FIGURE 39.9 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.

Do these data support the hypothesis that a starchy diet favors duplications of the AMY-1 gene?

To determine: The connection between the given data and the hypothesis based on starchy diet and AMY-1 gene duplication.

Introduction: An enzyme present in saliva that initiates or mediates the hydrolysis of starch into simpler sugar molecules are called as salivary amylase. AMY-1 is the gene that encodes for the salivary amylase enzyme. Humans possess this gene but copy number of that particular gene highly depends on their dietary habits. Varied number of the copy numbers of AMY1 genes is observed among the people. The people consuming high starchy diets have more copies of AMY1 gene when compared to the people with less starchy diets.

Refer Figure 39.9 “Number of copies of AMY-1 gene among members of cultures with high-starch or low-starch diets”, in the textbook. It gives the information about cumulative proportion of individuals versus AMY-1 diploid gene copy number found in them. The variations in copy numbers of salivary amylase (AMY-1) gene was tested among peoples of seven traditional groups that differ in their traditional food habits. They chose individuals with high starchy diet (Hadza, European American, and Japanese) and with low starchy diet (Yakut, Mbuti, Biaka, and Datog). Researchers observed a great difference in the enzyme copy number in the individuals of different populations.

The given graph suggests that the presence of copy numbers of AMY-1 gene depends on the foods taken by the members of a population...