Lamarck proposed an erroneous evolutionary theory called Lamarckism or the inheritance of acquired characteristics. This theory suggested that organisms could pass on to their offspring traits or characteristics acquired during their lifetime.

For example, Lamarck proposed that giraffes developed long necks because they stretched their necks to reach leaves on tall trees. However, modern evolutionary theory, based on the work of Charles Darwin, shows that evolution occurs through natural selection and the transmission of genetic variations, rather than the inheritance of acquired characteristics.