This chapter contribution to Scientific American was originally published as “These Truths Are Not Self-Evident—but They’ve Been Firmly Established Over and Over by Scientific Research” (November, 2016). It was co-authored by Michael Shermer, Harriet Hall, Ray Pierrehumbert, Paul Offit, and Seth Shostak.

In a letter to his friend the botanist Joseph Hooker, dated January 14, 1844, Charles Darwin recalled from his voyage around the world in the HMS Beagle: “I was so struck with distribution of Galapagos organisms &c &c…that I determined to collect blindly every sort of fact which cd bear any way on what are species.” After five years at sea and nine years at home thinking about the origin of species Darwin concluded: “At last gleams of light have come, & I am almost convinced, (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.”

Like confessing a murder. Dramatic words. But it doesn’t take a rocket scientist—or an English naturalist—to understand why a theory on the origin of species by means of natural selection would be so controversial: if new species are created naturally—not supernaturally—what place, then, for God? No wonder Darwin waited 20 years before finally publishing his theory in 1859, and why more than a century and a half later people of some religious faiths still find the theory threatening. But that 150+ years have brought together so much evidence in support of the theory that it would be truly astonishing if it turned out not to be true—on par with doubting the Big Bang origin of the universe or the germ theory of disease. Why? Because of a convergence of evidence from many lines of inquiry.

Cosmologists, for example, reconstruct the history of the universe through a convergence of evidence from astronomy, astrophysics, planetary geology, and physics. Geologists reconstruct the history of the Earth through a convergence of evidence from geology, geophysics, and geochemistry. Archeologists piece together the history of civilization through a convergence of evidence from pollen grains, kitchen middens, potshards, tools, works of art, written sources, and other site-specific artifacts. As a historical science, evolution is confirmed by the fact that so many different lines of evidence converge to this single conclusion. Independent sets of data from geology, paleontology, botany, zoology, herpetology, entomology, biogeography, comparative anatomy and physiology, genetics and population genetics, and many other sciences each point to the conclusion that life evolved. (continue reading…)