an evolutionary doctrine proposed by A. Weismann in the 1880’s and 1890’s, during the initial period of the formulation of genetic science.
Neo-Darwinism is based on two hypotheses: the continuity of the germ plasm and germ selection. The first hypothesis states that there exists a continuous, potentially “immortal” germ plasm that is modified primarily as a result of the combination of parental germ cells. Germ selection extends the principle of natural selection to hypothetical heriditary units, called determinants, within the germ cells. New life forms arise by virtue of the selection of determinants. It is postulated that the uneven distribution of determinants in the offsprings’ germ cells is suggestive of the determinants’ having emerged from a struggle within the parents’ germ cells. Darwinian natural selection is viewed as a check on unfit forms that arise in the process of germ selection.
Correct in its rejection of the inheritance of acquired traits, neo-Darwinism emphasizes the mosaicism of an organism’s tissues and the independent nature of the occurrence of modifications in individual traits over the course of evolution. Weismann’s ideas on the inertness, conservation, and fragmentation of hereditary matter, and on the role of independent hereditary units in the determination of individual traits were subsequently proved to be fruitful working hypotheses that eventually were developed in the science of modern genetics. However, Weismann’s view, an attempt to both link the findings of the new science of genetics with the older theories of evolution and to supplement Darwin’s idea of natural selection, turned out to be for the most part erroneous.
The term “modern Darwinism,” that is, a synthesis of population genetics and classical Darwinism, is sometimes used interchangeably with “neo-Darwinism.” This is a misuse of terms that is unfortunate and incorrect from a historical point of view.
A. V. IABLOKOV