Adaptationism

Adaptationism is an approach to evolutionary explanation that treats natural selection as the primary cause of biological traits and their apparent design.

Neutral theory of molecular evolution: The theory that most molecular evolutionary changes are selectively neutral and spread through genetic drift. It challenges the assumption that most evolutionary change reflects adaptation by selection.
Natural selection: The process by which heritable differences that affect reproductive success become more or less common across generations. It is the central causal process adaptationist explanations invoke.
Charles Darwin: The English naturalist who developed the theory of evolution by natural selection. Darwin made selection a central explanation for organisms’ apparent fit to their environments.
Male peacock's tail: The elaborate tail feathers of male peafowl, associated with courtship and sexual selection. Its costs and mating effects make it a classic test of selection-based explanations.
Adaptationist programme: A research strategy that explains biological traits by formulating and testing hypotheses about their adaptive functions. It distinguishes systematic adaptation research from merely assuming every trait is optimal.
Genetic drift: Random changes in allele frequencies caused by sampling in finite populations. It can change traits or gene frequencies without producing adaptations.
Adaptation: An inherited trait shaped by natural selection because it improved reproductive success in past environments. It is the outcome adaptationism most often seeks to explain.
George C. Williams: The American evolutionary biologist who clarified the gene-centered logic of natural selection and criticized weak adaptation arguments. His 1966 book set demanding standards for attributing traits to selection.
Peppered moth evolution: The change in frequency of dark and pale peppered moth forms as industrial pollution altered camouflage conditions. It demonstrates how environmental change can favor a specific inherited trait.
Just-so story: An evolutionary explanation that fits a trait after the fact without sufficiently testing competing causes. The label captures a central risk in adaptationist reasoning.

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