Concept
Exaptation
Overview
Exaptation or co-option is a shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour.
Bird feathers are a classic example. Initially they may have evolved for temperature regulation, but later were adapted for flight. When feathers were first used to aid in flight, that was an exaptive use. They have since then been shaped by natural selection to improve flight, so in their current state they are best regarded as adaptations for flight. So it is with many structures that initially took on a function as an exaptation: once molded for a new function, they become further adapted for that function.
Interest in exaptation relates to both the process and products of evolution: the process that creates complex traits and the products (functions, anatomical structures, biochemicals, etc.) that may be imperfectly developed. The term "exaptation" was proposed by Stephen Jay Gould and Elisabeth Vrba as a replacement for "pre-adaptation", which they considered to be a teleologically loaded term (i.e., it falsely implies that adaptation, or evolution generally, acts in pursuit of some goal).
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
Found by search and not yet checked by a person; they may only mention the idea in passing.
318) 'is called that of _individual_ preformation or the evolution theory: the system which regards them as products is called Epigenesis.--which might also be called the theory of _generic_ preformation, considering that the productive powers of the générants follow the inherent tendencies belonging to the family characteristics, and that the specific form is therefore a 'virtual' preformation, in this way the…
Georg Wilhelm Friedrich Hegel, The Logic of Hegel
States what Exaptation is.
"Utility" in respect of the acceleration of the speed of evolution, is a different kind of "utility" from that which is understood to mean the greatest possible stability and staying power of the evolved creature. "Useful" in the sense of Darwinian biology means: that which favours a thing in its struggle with others.
Friedrich Wilhelm Nietzsche, The Will to Power
States what Exaptation is.
In order of conspicuousness, though not in order of time, there come first those arrangements of parts which characterize the mature organism; an account of which, originally called Anatomy, is now called Morphology. Then come those successive modifications through which the organism passes in its progress from the germ to the developed form; an account of which is called Embryology. The structural changes which any…
Herbert Spencer, The Principles of Biology, Volume 1
States what Exaptation is.
Related ideas
- Virus
- Mutation
- Natural selection
- Stephen Jay Gould
- On the Origin of Species
- Charles Darwin
- Evolution
- Teleology in biology
Place in the tradition
Part of Consciousness.