"Mismatch theory" is based on the idea that organisms possess many traits (including behavioral patterns) that have been preserved by natural selection because of their adaptive function in a specific environment [sometimes called the environment of evolutionary adaptedness (EEA)] which for most of a species' evolutionary history might have been very unlike that in which it now finds itself. "Ancient" adaptive traits are thus frequently "mismatched" to the current environment -- and organisms thus find themselves doing the best they can to deal with contemporary stimuli using the traits they do possess. [more on mismatch theory]

(EEA) is the ensemble of physical and social conditions in which a particular trait was naturally selected (Tooby and Cosmides, 1990. The past explains the present: Emotional adaptations and the structure of ancestral environments. Ethology and Sociobiology 11:375-424; idea of EEA discussed on pp 386-387).

Clearly, any differences between the EEA and the present environment could be a source of stress for which contemporary animals would try to compensate. [such attempts to compensate --to enhance fitness-- are what drive evolution]


"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."


Researchers studying birds called great tits report evidence ... suggesting that the ability to change one's behavior when environmental conditions change runs in families and, when it confers a survival advantage, that this trait will be selected for over time.
Climate change can lead to mismatches in the seasonal responses of predators and prey. During the last 30 years, the growing season for the caterpillar prey of Dutch great tits occurs earlier in the year, so that the peak of caterpillar abundance is reached before the predator chicks are at their most voracious. Nussey (et al. 2005) report that "Theoretical and laboratory research suggests that phenotypic plasticity can evolve under selection. However, evidence for its evolutionary potential from the wild is lacking. We present evidence from a Dutch population of great tits (Parus major) for variation in individual plasticity in the timing of reproduction, and we show that this variation is heritable. Selection favoring highly plastic individuals has intensified over a 32-year period. This temporal trend is concurrent with climate change causing a mismatch between the breeding times of the birds and their caterpillar prey. Continued selection on plasticity can act to alleviate this mismatch. (Science, Vol 310, Issue 5746, 304-306 , 14 October 2005) (News of the Week – Science, 14 October 2005. “Better Habits Sometimes Heritable” by Elizabeth Pennisi)

We must, however, acknowledge, as it seems to me, that man with all his noble qualities... still bears in his bodily frame the indelible stamp of his lowly origin. Charles Darwin
The present environment may be very different from the EEA in which a particular trait was selected: what was once adaptive may no longer be -- more on "mismatch theory"