The synthetic theory. Origin of species

The synthetic theory of evolution took shape in the 20th century from the union of classical Darwinism with genetics, population genetics, ecology and systematics (scientists such as S. Chetverikov, R. Fisher, S. Wright, J. Haldane, T. Dobzhansky, J. Huxley, E. Mayr and I. Schmalhausen contributed). Main principles: 1) the elementary unit of evolution is the population, not the individual; 2) the elementary evolutionary event is a change in the gene pool of a population (a change in allele frequencies); 3) the evolutionary material is mutational and combinative variation; 4) the factors are mutations, gene flow (migration), genetic drift, population waves, isolation and natural selection; 5) the only directing factor is natural selection; the others are random; 6) evolution usually proceeds gradually (sometimes, for example with polyploidy, a new species arises in a few generations); 7) a species is a system of populations and subspecies; 8) evolution is divergent: several species arise from one; 9) microevolution is change within a species (a new population, subspecies, species), observed directly; macroevolution is the origin of taxa above species (genus, family, order, class), takes millions of years and is studied by indirect evidence (fossils, comparison); macroevolution is a continuation of microevolution, with the same factors. Modern evolutionary biology is enriching this theory with molecular genetics, genomics and evolutionary developmental biology (evo-devo).