ABSTRACT
Neurobiological theories of drug use are deeply intertwined with those of reward-based learning. Drug reward requires an evolutionary explanation: unlike food, sex, and other natural rewards, drugs, at first glance, do not make an obvious contribution to an animal’s survival or reproduction. Basic human anatomy prioritizes toxin defense, and taste buds are on the front line. Taste is responsible for evaluating the nutritious content of food and preventing the ingestion of toxic substances. The widespread recreational use of, and addiction to, several neurotoxic plant pesticides is extremely puzzling, to say the least. The chapter proposes that drug toxicity explains dramatic age and sex differences in drug use. It explores possible resolutions of the paradox of drug reward that are grounded in the neurotoxic properties of common recreational drugs. Popular recreational drugs are neurotoxic pesticides, varieties of which have infused the diets of human ancestors.
