The theory of natural selection and the survival of the fittest can be used to justify existing inequalities and injustices and may give weight to racism, elitism, domination and exploitation. Darwin's theory only concerned biological evolution; social Darwinism developed afterwards and was short-lived – but the heritage of these two aspects of the theory is paralleled in modern genetic arguments explaining inequalities and the naturally superior nature of some races (such as greater development and achievement in one society or social group as opposed to another).
The theory of evolution was developed by Darwin and Wallace in the mid-19th century. It gave rise to social Darwinism which developed in the late 19th century with the writings of Herbert Spencer, Walter Bagehot, and William Graham Sumner. In the second half of the 20th century scientists have discovered a number of problems in the theory, one of the more notable being that the theorized evolutionary time scale requires enormous spans of centuries for change, whereas fossil evidence shows change in inexplicably (relatively) short periods. Thus creationists, those that uphold the idea that God (that is a conscious Being with will and mind) created this world, and modern creationists, who assert that this Being (and helpers) managed the Creation, have become vocal in the Abrahamic religions of Judaism, Christianity and Islam to point out that the evolutionary theory in all its aspects is unproven.
The concept of creation in itself does not imply opposition to that of evolution, if that means only a gradual process whereby one kind of living creature changes into something else. A Creator might have employed such a process as a means of creation. 'Evolution' only contradicts 'creation' only when it is explicitly or tacitly defined as fully naturalistic evolution, meaning evolution that is not directed by any purposeful intelligence. 'Creationists', who believe that God created the earth, should not be confused with 'creation-scientists' who hold to a literal six-day creation despite abundant contrary evidence. The rules of argument surrounding these controversial issues are however structured to make it virtually impossible to question whether what is stated about evolution is true or not. Most adherents of evolution disagree amongst themselves about virtually every important part of Darwin's theory, although they close ranks against outsiders suggesting that there may be a God involved in the process.
Some imprudently and indiscreetly hold that evolution, which has not been fully proved even in the domain of natural sciences, explains the origin of all this, and audaciously support the monistic and pantheistic opinion that the world is in continual evolution. Communists gladly subscribed to this opinion so that, when the souls of men have been deprived of every idea of a personal God, they may the more efficaciously defend and propagate their dialectical materialism. Such fictitious tenets of evolution which repudiate all that is absolute, firm and immutable, have paved the way for the new erroneous philosophy which, rivaling idealism, immanentism and pragmatism, has assumed the name of existentialism, since it concerns itself only with existence of individual things and neglects all consideration of their immutable essences. Some however rashly transgress this liberty of discussion, when they act as if the origin of the human body from preexisting and living matter were already completely certain and proved by the facts which have been discovered up to now and by reasoning on those facts, and as if there were nothing in the sources of divine revelation which demands the greatest moderation and caution in this question. (Papal Encyclical, Humani Generis, 12 Ausut 1950).