An exaptation is a trait that evolved for one purpose but was later co-opted for a different function. In essence, it's a repurposing of an existing feature for a new use.

What are the main features of an exaptation?

• Evolutionary Re-purposing: A trait originally evolved for one function is adapted for a new, often unrelated, function.
• No Original Adaptation: The trait may not have been initially optimized for its current function.
• Co-option: The trait is "co-opted" or adopted for a new purpose through natural selection.

Why is an exaptation important?

• Evolutionary Novelty: Exaptations can lead to the evolution of novel traits and body plans.
• Adaptive Radiation: They can contribute to adaptive radiation, where a single species evolves into many different species.
• Understanding Evolutionary History: Exaptations can provide insights into the evolutionary history of organisms and the constraints and opportunities that shape their development.

What are the applications of an exaptation?

• Evolutionary Biology: Exaptations are used to explain the evolution of diverse traits and body plans.
• Developmental Biology: They can help us understand how developmental pathways can be modified to produce new traits.
• Paleontology: Exaptations can be used to interpret fossil evidence and reconstruct evolutionary relationships.

Example

Feathers are a classic example of an exaptation. They are thought to have originally evolved for insulation in dinosaurs, but later were co-opted for flight in birds.

Critical comments

• Identification: Identifying exaptations can be challenging, as it often requires inferring the original function of a trait.
• Contingency: Exaptations are often contingent on historical events and may not be predictable.
• Constraints: The structure and function of a trait may be constrained by its evolutionary history, limiting its potential for exaptation.