A maladaptation is an adaptation that is (or has become) less helpful than harmful. It is a term used when discussing both humans and animals in fields such as evolutionary biology, biology, psychology (where it applies to behaviors and other learned survival mechanisms) and other fields where adaptation and responsive change may occur. Like adaptation, it 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 less appropriate or even become on balance 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 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.

Examples for maladaptations:

• During periods of climate change, such as global warming or cooling, 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 or man-made barriers.
• Resistance to antibiotics is usually an adaptation/maladaption issue from the point of view of infective agents: the initial disease agents are well adapted to the physiological conditions of their host and can proliferate. When antibiotics are employed, those organisms that have no or little resistance against them are at a disadvantage. However, being able to detoxify antibiotics comes at a price: the mechanisms conferring antibiotic resistance (e.g. beta-lactamase) are rarely useful for any other purpose. Hence, energy that would otherwise be available to grow and reproduce is diverted for antibiotics detoxification. To an infective organism, it is thus a trade-off between being able to outgrow resistant strains ones in the absence of antibiotics, and being able to detoxify antibiotics if these are encountered. An evolutionary stable strategy strategy is thus not possible, if antibiotics are not used indiscriminately.
• Dodos were able to cope with the climate conditions on Mauritius. There, during parts of the year semiarid conditions predominate, and plants produce relatively little biomass that dodos would have used as food (such as fruits), whereas in the wet season there is an overabundance of food. Dodos apparently adapted to this by building up fat deposits when food was plentiful, and adjusting their breeding cycle to climate conditions. Confronted with humans and introduced predators, this proved ultimately fatal: humans would believe the fat dodos good to eat and hunt them, or simply kill them for fun because of their funny appearance and awkward movements. The breeding cycle, which originally ensured that as little effort as possible was wasted in reproduction made them vulnerable to the introduced pigs and monkeys, as there was little possibility for a dodo whose egg had been destroyed to re-nest before the year's reproductive season was over.
• See Ecological traps

es:Maladaptación pt:Má adaptação sr:?????????????