The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for at least the past 3000 million years. Until the middle of the 18th century it was generally believed that each species was divinely created and fixed in its form throughout its existence (see special creation). Lamarck was the first biologist to publish a theory to explain how one species could have evolved into another (see lamarckism). But it was not until the joint publication in 1858 of the paper by Darwin and Wallace outlining a theory of evolution by natural selection, and Darwin’s On the Origin of Species in 1859, that special creation was seriously challenged. Unlike Lamarck, Darwin and Wallace proposed a feasible mechanism for evolution and backed it up with evidence from the fossil record and studies of comparative anatomy and embryology (see darwinism; natural selection). The modern version of Darwinism, which incorporates discoveries in genetics made since Darwin’s time, remains the most acceptable theory of species evolution (see also punctuated equilibrium). See also macroevolution; microevolution; mosaic evolution. See Appendix 8 for further sources of information.

https://evolution.berkeley.edu/evolibrary/home.php The evidence for and mechanisms of evolution, from Understanding Evolution, created by the University of California Museum of Paleontology