Environment of Evolutionary Adaptedness (EEA)
The natural habitat or environment to which humans were originally adapted. This is assumed to be the hunter-gatherer lifestyle and habitat where humans spend over 99% of their evolutionary history. However, it must be recognized that each adaptive trait has its own unique evolutionary history and therefore its own particular EEA. For example, the human fear response is particularly sensitive to signals associated with the presence of snakes and spiders. This reflects the fact that these threats were prevalent in the ecological environments of our ancestral past. Human reasoning, however, exhibits characteristics reflective of the social environment of the past, where concerns about cheating on social agreements would have been of particular concern. So while both of these adaptations reflect elements of our hunter-gatherer origins, they reflect different aspects of those origins: one ecological, one social.