Overview

Waddington and Lewontin both objected to any portrayal of organisms as passive victims of selection. They viewed organisms as active agents, both in their own development and in their evolution, with their activities a major determinant of fitness differences and hence of natural selection.

Agency is the intrinsic capacity of individual living organisms to act on, and in, their world, and thereby to modify their experience of it, including in ways that are neither predetermined, nor random (Laland et al. 2019). It is an essential and inescapable aspect of nature. Living organisms are not just passively pushed around by external forces, but rather they act on their world according to intrinsically generated but historically informed capabilities. Organisms are self-building, self-regulating, highly integrated, functioning, and (crucially) “purposive” wholes, which through wholly natural processes exert a distinctive influence and a degree of control over their own activities, outputs, and local environments. Indeed, organisms must have these properties in order to be alive (Schrödinger 1944).

Use of the term ‘agency’ in niche construction theory does not imply conscious, sentient, or deliberate action, nor vitalism (or any mystical power that imbues living tissue), nor a rejection of mechanistic explanation, nor the belief that living organisms possess any desire to evolve, or achieve some final state. Human niche construction sometimes is conscious, intentional, and deliberate, and may set out to achieve longer-term goals, but these are neither necessary nor defining characteristics of niche construction. Even for humans, a great deal of our niche construction is non-intentional. The claim that organisms are “purposive” means nothing more than that organisms exhibit goal-directed activities, such as foraging, courtship, or phototaxis, which are entirely natural tendencies with short-term local objectives, and that have themselves evolved.

In acknowledging the legacy of past natural selection in shaping how contemporary organisms manifest their agency in the world, niche construction theory rejects the suggestion that the actions of organisms are fully explained by prior selection. Organisms are influenced, but seldom if ever fully determined, by their genes, and their activities are shaped by developmental information-gaining processes as well as selection. They are not merely objects through which the causal explanatory power of natural selection flows; organisms are active agents that transduce and filter genetic and environmental inputs.