What counts as an alternative to the Darwinian view of biological origins depends on what one takes Darwinism to be. To advocates of “special creation,” Darwinism refers to its author’s claim that all organisms evolved from a single common ancestor. Among evolutionists themselves, however, Darwinism refers to natural selection, Darwin’s distinctive mechanism for explaining species transformation and common descent. Creationist challenges are not our topic. Challenges to natural selection as causally explaining it are.

As it happened, natural selection inserted itself into an already lively debate about evolutionary mechanisms (Desmond 1989; Secord 2000). Darwin’s was a powerful idea, but not powerful enough to knock out all of its rivals, which have reasserted themselves whenever a version of Darwinism that has organized evolutionary research for a time – and there have been several – runs into trouble. Trouble can come from new empirical discoveries, from the discrediting of false claims or assumptions on which Darwinians had relied, or from research methods that prove flawed.

Darwinism’s currently established but aging version, the modern evolutionary synthesis, has been facing challenges of all three sorts since the 1980s. The modern synthesis was first articulated just before and during World War II on the basis of technical work done earlier (Dobzhansky 1937 ; J. S. Huxley 1942 ; Mayr 1942 ; Simpson 1944). It claimed to unify all biological fields by integrating natural selection with genetics, about which neither Darwin nor nineteenth-century Darwinians knew anything.