Evolution

Evolution, process by which organisms have changed and species have arisen and disappeared since the origin of life. The formulation of the theory of evolution in its modern form is credited to Charles Darwin and Alfred Russel Wallace, 19th-century British scientists who proposed that the central mechanism of evolution was natural selection. In essence, this theory states that life forms with certain characteristics tend to reproduce in larger numbers and survive environmental changes better than other, similar life forms that lack these characteristics. These forms then tend to become dominant within the population, and the characteristics are inherited by subsequent generations. Integral to the theory is the notion that all species of life on earth are interrelated, ultimately having common ancestry.

Today, the evidence for evolution is overwhelming and comes from many branches of science, including biology, anatomy, embryology, paleontology, biochemistry, genetics, and other fields. The discovery of the phenomenon of genetic mutation and the increased understanding of the structure of genes has helped to answer many of the questions about the mechanisms of the changes that life forms undergo. The field of ecology has given new insight into how different species of plants and animals interrelate with and affect one another. Although the theory of evolution has undergone various important changes since the 19th century, it still rests basically on the foundations laid down by Darwin and Wallace and has been one of the most successful and influential theories in the history of science.

See also: Darwin, Charles Robert.