In evolutionary biology, preadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose. One example of preadaptation is dinosaurs having used feathers for insulation and display before using them to fly, or sweat glands in mammals being transformed into mammary glands.

Another example is the hypothesis proposed by zoologist Jonathan Kingdon that before early humans became bipedal, they began engaging in squat feeding, i.e. turning over rocks and leaves to find insects, worms, snails and other food. Consequently, they adapted flatter feet than were necessary in their previous tree-dwelling ancestors, since that makes squatting much easier. Flatter feet are also extremely useful for bipedal animals, so they can be described as a preadaptation to bipedalism, even though (or rather because) the adaptation had nothing to do with bipedalism originally.

Some biologists dislike the term 'preadaptation' as it could imply an intentional plan, which is contrary to the undirected nature of evolution. Some alternative terms that have been suggested include "co-option" and exaptation.

Source

• Bickerton, Derek (2000). "Biomusicology and Language Evolution Studies", The Origins of Music. Cambridge, Mass: A Bradford Book, The MIT Press. ISBN 0-262-23206-5.