Cooption, exaptation, and preadaptation, studied in depth by Stephen Jay Gould in the 80’s, are related terms referring to shifts 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 in another environment. Exaptations are common in both anatomy and behavior. A classic example is feathers, which initially evolved as insulation, were co-opted for display, and eventually were co-opted for use in bird flight. Interest in cooption relates to both the process and product of evolution: the process that creates complex traits and the product that may be imperfectly designed.

This idea of the imperfection of the evolutionary chain, and the swapping of behaviors begins to define a ‘minor biology’ which is critical to understanding the interrelation of features and behaviors in species. Their relation is in fact fluid and messy, which brings into question ‘clean’ models of natural selection being bandied around by many biologically-minded architects.

(Image: The Toucan’s large beak is not a result of sexual selection or edible fruit size as often assumed. It is rather a thermoregulating device—a massive radiator—which dumps heat during flight. The thermoregulatory function is an exaptation, a beneficial byproduct, of other evolutionary pathways.)