Starch, a complex carbohydrate, is a vital source of nutrition for many mammals. Humans farm it in the form of rice, wheat, corn, potatoes and oats. Rats comb our garbage piles for scraps of pizza and bread. Wild boars root for tubers. Now, a new study is providing insight into how the pursuit of starch may have driven evolutionary adaptations in these and other hungry mammals. The research, conducted on 46 mammal species, focuses on a biological compound called amylase, which is produced by humans and other animals to break down starch. The study finds that over the course of mammalian evolution, the genetic machinery that teaches the body how to make amylase has been something of a chameleon. It has evolved in different ways in different beasts, and it’s capable of changing rapidly, possibly in accordance with what animals eat. The study finds that mammals with starchy diets tend to have more copies of the amylase gene, which carries instructions for building amylase, than mammals that consume little starch (at least among the species studied). The research also presents evidence that evolutionary changes related to amylase -- including duplications of the amylase gene and the ability to produce amylase in saliva -- may have arisen independently in some different species. Called convergent evolution, this phenomenon often signals a particularly useful adaptation. Overall, the study paints a colorful picture of the evolutionary history of amylase across mammals, ranging from humans, dogs and house cats to hedgehogs and ring-tailed lemurs, along with baboons that store food in their cheeks.
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