Lamarckism is a theory of evolution proposed by the French biologist Jean-Baptiste Lamarck in the early 19th century. It suggests that organisms can pass on traits acquired during their lifetime to their offspring. For example, if an animal develops stronger muscles from frequent use, its descendants may inherit those stronger muscles. This idea contrasts with Darwinism, which emphasizes natural selection as the primary mechanism of evolution. While Lamarckism was influential in its time, it has largely been discredited in modern biology, as genetic inheritance is understood to be based on DNA rather than acquired characteristics.