Exaptation has undergone its own quite radical evolution since it was introduced/developed just over 40 years ago.
Exaptation 1.0 – was focused on the creature, exclusive of the environment, how physical features could be co-opted for new purposes, and how single acts of exaptation lead to a process of novel adaptation.
The problems with this were: (1) the focus on the creature missed creature-environment co-creation, (2) the metaphors of “fitting” & “adaptation” reinforced a separation between creature & environment (with fitness being literally how well a creature fits or adapts to a pre given environmental niche), (3) the implicit assumption that a single exaptation can lead to a new adaptive process did not consider the linked & iterative network of exaptations involved in change, & (4) “with each exaptation we are still faced with the impossibility of an original selection-for” (Tomlinson).
Exaptation 2.0 & 3.0: from the perspective of the evolutionary theory of radical niche construction & affordances, creatures neither live in “external” environments, nor do they “adapt” or “fit” to pre-existing environments.
Living beings are in a dynamic relational landscape of affordances (the relation between embodied skills & context relevant aspects of the environment that give rise to specific possibilities for action). Thus environmental niches do not pre-exist an organism – they are co-specifying & co-determining. To talk of an organism is always to talk of a co-determining environment. Thus, it is “is not the process in which the external environment molds passive form. Rather it is a process by which the organisms respond to, and in the process, create their own system of affordances” (Walsh).
All living beings are involved in co-shaping & co-determining their niche – their landscape of affordances. Lewontin, a strong critic of the metaphors of fitness and adaptation, proposed a “constructivist” set of metaphors as being more appropriate. Creatures do not adapt to a pre-existing niche – they are co-constructing their niche as this niche is constructing them.
Exaptation in this context is then no longer a physical feature but part of how the potentials for action of an affordance always exceeds current use or, how their is a potential for the construction of novel affordances by changing aspects of the relation. Additionally as an affordance it is a process within the processes of niche construction & its feed forward cycles.