1. The idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring.
2. The belief in the transmissibility or heritability of acquired characteristics.

Named after the French biologist Jean-Baptiste Lamarck (1744–1829), who incorporated the action of soft inheritance into his evolutionary theories.

He proposed that individual efforts during the lifetime of organisms were the main mechanism driving species to adaptation, because it was theorized that they would acquire adaptive changes and pass them on to their offspring.