[Evidence for evolutionary changes in ontogeny: paleontological, comparative-morphological, and molecular aspects]

It has been noted that the integration of modern data of paleontology, comparative morphology, developmental biology, and molecular genetics forms the basis for understanding the mechanisms of evolutionary transformations of ontogeny. Paleontological and morphological evidence of the evolutionary changes in ontogeny are considered based on the data of cell and molecular biology and developmental genetics. It is shown that reorganizations of gene regulatory cascades (primarily Hox genes) play a key role in the evolution of the axial organization of animals and modifications of the limb structure of metazoans, whereas the emergence and development of new types of structures was apparently determined by the emergence of new populations of stem cells in embryogenesis (for example, neural crest cells in the evolution of vertebrates).