Exaptation, a key concept in evolutionary biology, refers to the repurposing of existing traits for new functions. This process plays a significant role in both biological and cultural innovation, enabling rapid evolutionary responses. Its identification, however, is complicated due to the complexity of historical evolutionary pressures.
Definition
Exaptation is the process by which features acquire functions for which they were not originally adapted or selected.
Adaptation vs Exaptation
Unlike adaptation, where a trait evolves in response to a specific selection pressure, exaptation involves traits evolving for one purpose and later being co-opted for a new use.
Types of Exaptation
There are two types, namely pre-adaptations (traits that serve a particular function but incidentally lead to an organism being well-suited for another function) and spandrels (traits that did not arise due to natural selection for their current use, but rather as a byproduct of the evolution of some other characteristic).
Examples of Exaptation
Feathered wings of birds, which are believed to have evolved initially for thermal regulation or mate attraction before being used for flight, is a classic example of exaptation. Another example is the human brain’s ability to read, which evolved long after the brain itself did.
Exaptation and Innovation
Exaptation is often associated with biological innovation, and has been proposed as a key mechanism in the evolution of complexity.
Role in Rapid Evolution
Exaptation can enable rapid evolution when environments change quickly, as organisms can repurpose existing traits for new challenges.
Exaptation in Cultural Evolution
The concept of exaptation is also used in studying cultural evolution and innovation, where ideas and tools are repurposed for new uses.
Critiques and Limitations
Critics argue that distinguishing between adaptations and exaptations can be challenging due to the difficulty of inferring historical selection pressures. Some also argue that the concept is less helpful than focusing directly on current functionality.
