The obsolete theory that offspring can inherit physical or behavioral characteristics from a parent that the parent acquired during its life. For example, a giraffe which stretches its neck to reach leaves at the top of a tall tree and thus ends up with a slightly longer neck can pass on the long neck trait so that its offspring also have long necks and can stretch it even longer. The theory, now known to be incorrect, was popularized by Jean-Baptiste Lamarck (1744-1829) and played an important role in the history of the study of evolutionary biology.