"Coined by psychoanalyist John Bowlby (1907-1990), the Environment of Evolutionary Adaptedness (EEA) is the sum of all selection pressures faced by an organisms ancestors in "recent" times. Evolutionary psychologists equate the human EEA with the Pleistocene, arguing that the complex set of mental adaptations proposed by the modular theory of mind arose mostly during this span.
It's important to note that the EEA is distinct from our modern environment, with its permanent settlements, agriculture, large interacting populations, and mass comunication. Human society in the EEA consisted of small (by today's standards) hunter-gatherer tribes, all of whose members knew each other intimately. Evolutionary psychologists expect innate human behavioral tendancies to be adapted to the EEA, and not necessarily to the modern environment.
This recognition often results in novel hypotheses about adaptive by-products. For example, motion sickness, an all-too-common phenomenon in our modern world of cars and airplanes, has been explained as a by-product of an adaptation serving to clense the body of neurotoxins which would have been accidently consumed in the EEA. That is, the horizon disturbance we experience when driving in an automobile, the sort of motion that makes one nauseous, is an unintentional mimicry of the same sort of disturbance one made ill from consuming poisons would experience."