Adaptationism

Adaptationism is the research program and methodological stance in evolutionary biology that treats the traits of organisms as adaptations — solutions produced by natural selection to functional problems posed by the environment. For the adaptationist, the right question to ask about any heritable trait is: what is it for?

The program has been productive and empirically well-supported for many traits, particularly complex morphological and physiological features. The eye, the kidney, and the vertebrate immune system are genuinely explicable as selection-optimised solutions to well-defined functional problems. Adaptationism's success here is real and should not be minimised by its critics.

The critique — launched most forcefully by Stephen Jay Gould and Richard Lewontin in their 1979 'spandrels' paper — is that adaptationism functions as an unfalsifiable commitment rather than a testable hypothesis. When an adaptationist story fails, the response is typically to generate a different story rather than to conclude that the trait is not an adaptation. This is not scientific reasoning; it is storytelling constrained only by the requirement to sound plausible.

The spandrels critique identified two real alternatives: traits may be developmentally or architecturally constrained rather than selected, and traits may be exaptations — features that currently serve a function different from the one that drove their evolution. Neither of these is an adaptationist story, and neither can be easily incorporated into adaptationism without abandoning the program's core commitment.

Adaptationism's most dangerous misapplication is in the human sciences, where 'evolutionary explanations' of social behaviour frequently confabulate adaptive stories for traits whose evolutionary history is entirely unknown.