Lamarckian Inheritance

Lamarckian inheritance holds that traits an organism acquires or strengthens during its own lifetime, through use, can be passed to its offspring; the standard illustration is a giraffe stretching to reach high leaves and passing a longer neck to its young. Jean-Baptiste Lamarck set out the idea in his 1809 Philosophie Zoologique as part of a broader theory of evolution. August Weismann's germ plasm theory in the 1880s argued that hereditary material in reproductive cells is walled off from changes in the rest of the body, and the rediscovery of Gregor Mendel's inheritance rules around 1900 supplied a mechanism, genes passed unchanged between generations, that explained heredity without requiring acquired traits at all. Repeated attempts to find real evidence for Lamarckian inheritance were explained away by other causes or found to be fraud, and the theory was abandoned in favor of natural selection acting on inherited variation.