Lamarck’s Two Legacies: A 21st-century Perspective on Use-Disuse and the Inheritance of Acquired Characters

Lamarck has left many legacies for future generations of biologists. His best known legacy was an explicit suggestion, developed in the Philosophie zoologique (PZ), that the effects of use and disuse (acquired characters) can be inherited and can drive species transformation. This suggestion was formulated as two laws, which we refer to as the law of biological plasticity and the law of phenotypic continuity. We put these laws in their historical context and distinguish between Lamarck’s key insights and later neo-Lamarckian interpretations of his ideas. We argue that Lamarck’s emphasis on the role played by the organization of living beings and his physiological model of reproduction are directly relevant to 21st-century concerns, and illustrate this by discussing intergenerational genomic continuity and cultural evolution.