Who proposed the theory of inheritance of acquired characteristics?

Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characteristics. The French naturalist described his evolutionary ideas most fully in Philosophie zoologique, published in 1809. He argued that organisms change in response to their environments, that frequently used organs become stronger, and that unused organs weaken. He further proposed that these changes could be passed to offspring.

This idea is often called Lamarckism or soft inheritance. The classic example is the giraffe, supposedly lengthening its neck by repeatedly stretching for leaves and passing the acquired trait to its young. Modern genetics rejected this general mechanism because changes acquired by an individual's body are not ordinarily encoded into reproductive DNA.

Lamarck was nevertheless important in the history of evolutionary biology. He was among the first scientists to present a coherent theory that species change over time. His work should not be confused with Charles Darwin's natural selection, which explains adaptation through inherited variation and differential survival and reproduction.