Darwin at 200.

C harles Robert Darwin was born on February 12, 1809 (the same day as President Abraham Lincoln). In 1859 Darwin published On the Origin of Species by Means of Natural Selection (1), his most important book and the one by which he has become best known to posterity. Thus, 2009 is a double anniversary: the 200th of Darwin’s birth and the sesquicentenary of Origin. Darwin is deservedly credited as the originator of the modern theory of evolution. In Origin he gathered the best available evidence for evolution: 2 chapters dedicated to the geological record, 2 chapters to biogeography, and 1 chapter to comparative anatomy and embryology. The other 9 chapters (I–VIII and XIII) are mostly dedicated to natural selection, the process that accounts for the adaptation, common descent, and diversity of organisms. He explains how natural selection works, discusses the role of hereditary variation (the mechanics of which were not well understood in Darwin’s time), and considers possible objections to his theory.