Maladaptation

In evolution, a maladaptation (ˌmælædæpˈteɪʃən) is a trait that is (or has become) more harmful than helpful, in contrast with an adaptation, which is more helpful than harmful. All organisms, from bacteria to humans, display maladaptive and adaptive traits. In animals (including humans), adaptive behaviors contrast with maladaptive ones. Like adaptation, maladaptation may be viewed as occurring over geological time, or within the lifetime of one individual or a group. It can also signify an adaptation that, whilst reasonable at the time, has become less and less suitable and more of a problem or hindrance in its own right, as time goes on. This is because it is possible for an adaptation to be poorly selected or become more of a dysfunction than a positive adaptation, over time. Note that the concept of maladaptation, as initially discussed in a late 19th-century context, is based on a flawed view of evolutionary theory. It was believed that an inherent tendency for an organism's adaptations to degenerate would translate into maladaptations and soon become crippling if not "weeded out" (see also eugenics). In reality, the advantages conferred by any one adaptation are rarely decisive for survival on its own, but rather balanced against other synergistic and antagonistic adaptations, which consequently cannot change without affecting others. In other words, it is usually impossible to gain an advantageous adaptation without incurring "maladaptations". Consider a seemingly trivial example: it is apparently extremely hard for an animal to evolve the ability to breathe well in air and in water. Better adapting to one means being less able to do the other. During periods of climate change—such as cooling or the currently experienced global warming—species that were well adapted in the original climate may be maladapted to the new climate and die out, if they are prevented from shifting their range due to geological barriers.