the origin of a group of organisms from a common ancestor; the basic concept in the theory of the evolution of the organic world.

Monophyletism may be visually represented by a genealogical tree that traces the development of organic nature and of phylogenetic relationships between natural groups. The tree of life originates from a common root, then divides into two trunks that correspond to the plant and animal kingdoms. From each trunk there emerges a succession of large trunks, the phyla, that gradually branch into smaller taxonomic groups: classes, orders, families, and, finally, genera consisting of clusters of separate branches, species.

C. Darwin supported the theory of monophyletism with data from animal and plant breeding. Analyzing the origin of extant breeds of domestic pigeons, he showed that their ancestor was a single species, the rock pigeon (Columba livid}. After Darwin, data from taxonomy, comparative morphology, physiology and biochemistry, embryology and genetics, and biogeography and paleontology indicated the monophyletic origin of most natural groups of the plant and animal kingdoms.

Applied to mankind, monophyletism denotes the common origin of all human races. The theory of monophyletism is the basis of contemporary taxonomy and of the study of the historical development of the plant and animal kingdoms.