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In most animals, taste has evolved to avoid all things bitter to prevent from eating something typically poisonous. The taste sensation is mediated by the binding of taste receptors, known as Tas2rs, with bitter compounds. Because plant tis-sues contain more toxins than animal tissues do, one may hypothesize that herbivores need more Tas2r genes than car-nivores to deal with the diverse toxins they encounter. Evolutionary geneticist Zhang and Li tested this hypothesis (Li and Zhang 2013). They identified Tas2r genes from the genome sequences of more than 50 vertebrate species including mammals, birds, reptiles, amphibians, and fishes. They then constructed evolutionary trees and estimated the loss and birth of Tas2r genes in vertebrate evolution. Finally, they classified all species into herbivores, omnivores, or carnivores and correlated the number of Tas2r genes in a species with its diet. Their anal-yses supported the hypothesis, showing that herbivores gen-erally have more Tas2r genes than do omnivores and carnivores. Thus, what you eat clearly shapes the evolution of your genes