Belief in the theory of evolution by natural selection. Core Darwinism has been defined by the biologist Richard Dawkins as ‘the minimal theory that evolution is guided in adaptively nonrandom directions by the nonrandom survival of small random hereditary changes’. The theory in its original form took wing from the observation of Malthus that although living organisms produce multiple offspring, adult populations remain relatively stable in number. Darwin realized that the different chances of survival of differently endowed offspring could account for the natural evolution of species. Nature ‘selects’ those members of a species best adapted to the environment in which they find themselves, much as human animal breeders may select for desirable traits in their livestock, and thereby control the evolution of the kind of animal they wish. In the phrase of Spencer, nature guarantees the ‘survival of the fittest’, although the phrase is misleading in suggesting that an original species, from which others evolve, may not itself continue to occupy some niche to which it is well enough adapted. The Origin of Species was principally successful in marshalling the evidence for evolution, rather than providing a convincing mechanism for genetic change, and Darwin himself remained open to the search for additional mechanisms, whilst also remaining convinced that natural selection was at the heart of it. It was only with the later discovery of the gene as the unit of inheritance that the synthesis known as ‘neo-Darwinism’ became the orthodox theory of evolution in the life sciences. See also creationism, Darwinian Population, evolutionary ethics, intelligent design, sociobiology.