Domesticated foods feed most of the world’s 7 billion people. Yet as common as domesticated plants and animals are today, we still do not understand why prehistoric people domesticated wild resources in the first place. Current debates center on the importance of population-resource imbalances: does domestication result from experimentation during times of plenty or from necessity during times of scarcity? Here we show that domestication in Eastern North America was preceded by significant increases in human population, suggesting that domestication occurred during times of resource scarcity caused by either competition for over exploitation of resources. These findings suggest that human modification of the environment occurs out of necessity, primarily when human populations outstrip their food supply.