Genetics and Evolution

Hugo de Vries believed that mutation causes evolution and not the minor variations that Darwin talked about. Mutations are random and directionless, whereas Darwinian variations are small and directional. De Vries called speciation by a single-step large mutation 'saltation' (jumping).

Fossils are remains of hard parts of life-forms found in sedimentary rocks. A study of fossils in different sedimentary layers indicates the geological period in which they existed and reveals that life forms varied over time. The study of fossils is known as paleontology.

Hugo de Vries put forth his idea of mutation based on his extensive hybridization experiments on the evening primrose (Oenothera lamarckiana). He proposed that large single-step mutations (saltations) are the causative agents of evolutionary speciation.