Exaptation
Note that the selection pressure upon a trait is likely to change if it is (especially, primarily or solely) used for a new purpose, potentially initiating a different evolutionary trajectory.
To avoid these ambiguities, David Buss et al. suggested the term "co-opted adaptation", which is limited to traits that evolved after cooption.
In some circumstances, the "pre-" in preadaptation can be interpreted as applying, for non-teleological reasons, prior to the adaptation itself, creating a meaning for the term that is distinct from exaptation.
[7][8] For example, future environments (say, hotter or drier ones), may resemble those already encountered by a population at one of its current spatial or temporal margins.
Cryptic genetic variation may have the most strongly deleterious mutations purged from it, leaving an increased chance of useful adaptations,[8][9] but this represents selection acting on current genomes with consequences for the future, rather than foresight.
As one of the oldest biological systems and being central to life on the Earth, studies have shown that metabolism may be able to use exaptation in order to increase fitness, given some new set of conditions or environment.
It is possible to look at a retroposon, originally thought to be simply junk DNA, and deduce that it may have gained a new function to be termed as an exaptation.
This may have occurred with mammalian ancestors when confronted with the Permian–Triassic extinction event about 250 million years ago and substantial increase in the level of oxygen in Earth's atmosphere.
More than 100 loci have been found to be conserved only among mammalian genomes and are thought to have essential roles in the generation of features such as the placenta, diaphragm, mammary glands, neocortex, and auditory ossicles.
In other words, the beginning of evolving a particular trait starts out with a primary adaptation toward a fit or specific role, followed by a primary exaptation (a new role is derived using the existing feature but may not be perfect for it), which in turn leads to the evolution of a secondary adaptation (the feature is improved by natural selection for better performance), promoting further evolution of an exaptation, and so forth.
One of the challenges to Darwin's theory of evolution was explaining how complex structures could evolve gradually,[24] given that their incipient forms may have been inadequate to serve any function.
By trapping air, primitive wings would have enabled birds to efficiently regulate their temperature, in part, by lifting up their feathers when too warm.
These individuals would in turn more successfully survive and reproduce, resulting in the spread of this trait because it served a second and still more beneficial function: that of locomotion.
Exaptation has received increasing attention in innovation and management studies inspired by evolutionary dynamics, where it has been proposed as a mechanism that drives the serendipitous expansion of technologies and products in new domains.
