Which is not one of Darwin four main ideas of natural selection?

One idea that is not one of Darwin's four main concepts of natural selection is the concept of "inheritance of acquired characteristics," which was proposed by Lamarck. Darwin's four main ideas include variation within populations, competition for resources, survival of the fittest, and the inheritance of favorable traits. Unlike Lamarck's theory, Darwin emphasized that traits are passed down through genetic inheritance rather than acquired through an individual's lifetime.