Beyond the Baldwin Effect: James Mark Baldwin’s ‘social heredity’, epigenetic inheritance and niche-construction

James Mark Baldwin is remembered today almost exclusively for his paper ‘A New Factor in Evolution’ (Baldwin, 1896a). The new factor, which he called ‘organic selection’ and which later became known as the Baldwin effect, was a process that could cause ‘accomodations’ the acquired adaptive responses of individual organisms to become hereditary. ‘Accomodations’ include physiological adaptations like calluses and, of much greater interest to Baldwin, learnt behaviors. The Baldwin effect differed from classic Lamarckian inheritance because it respected August Weismann’s doctrine of the ‘continuity of the germ plasm’ according to which modifications to somatic cell-lines can have no influence on the state of the germ cells. Viewed at the population level, the Baldwin effect would give the impression that the Lamarckian inheritance of acquired characters was taking place, but this impression would be an illusion no individual