Any feature that performs a function but was not produced directly (purposefully) for its current affordance. This is the universe we wish to explore — a universe of possibilities unknowable in advance found in and with everything.
For a more explicit definition of exaptations with examples refer to Emerging Futures Newsletter Volume 43: Defining Exaptations.
This is the evolutionary process of utilizing the unintended consequences (affordances) of a physical feature to novel ends.
Most, if not all, critical features of organisms evolved in this manner: wings, eyes, bones etc.
Darwin originally called these phenomenon “preadaptation,” but this suggest that the creature was somehow preparing for this novel features emergence (that it could know in advance about flight).
Recently, Stephen Jay Gould and Elizabeth Verba proposed that this be called: exaptation, because it is outside (the ex part of the term) adaptation.
Which is a beautiful way of describing creativity -- it is a process of novelty that is outside of fitting into any existing purpose.
Exapatation is a derivative of aptation.
A wing is a great example of exaptation in nature. A wing can be sexy, ward off predators, keep eggs warm, and be used for flight.
The wheel as an example of exaptation in innovation. The wheel is used for transportation, to generate power (watermill), or as a gear in an engine.
... is to ask yourself: "what else can this [any physical object] do?"
Which is the opposite of adaptation where some thing evolves in a way that improves its existing purpose— a change in degree if you will.
While a radical exapatation exceeds its immediate quantitative purpose to allow an unknown novel world to co-emerge.
We can thus summarize the space of exaptations:
1. Unintentional features: unintentional features will have one of two types of effects:
[a] In category effects (or at scale effects): this is when the unintended effect is in a similar space.
[b] Outside category effects (injections across scales) — this is where the most powerful exaptations are to be found— where they open new spaces of possibility: whale vision based on sonar from clicking, or how humming birds can sing with their wings.
2. Purposeless non-functional features: Every thing has many features that are just there. Perhaps in the making of your particular coffee cup the glaze just dripped a small amount. A little noise in the system that cause some slight but meaningful shift.
3. Invisible introductions: chance physical by-products can produce invisible introductions. These can also be in category or cross category effects.
4. Unintended effects of Intentional Features: this is the category that comes across from intentional features and effects.