Political interpretations

Darwin's fame and popularity led to his name being associated with ideas and movements which at times had only an indirect relation to his writings, and sometimes went directly against his express comments.

Caricature from 1871 Vanity Fair

Eugenics

Darwin was interested by his half-cousin Francis Galton's argument, introduced in 1865, that statistical analysis of heredity showed that moral and mental human traits could be inherited, and principles of animal breeding could apply to humans. In The Descent of Man Darwin noted that aiding the weak to survive and have families could lose the benefits of natural selection, but cautioned that withholding such aid would endanger the instinct of sympathy, "the noblest part of our nature", and factors such as education could be more important. When Galton suggested that publishing research could encourage intermarriage within a "caste" of "those who are naturally gifted", Darwin foresaw practical difficulties, and thought it "the sole feasible, yet I fear utopian, plan of procedure in improving the human race", preferring to simply publicise the importance of inheritance and leave decisions to individuals.
Galton named the field of study "eugenics" in 1883, after Darwin's death, and developed biometrics. Eugenics movements were widespread at a time when Darwin's natural selection was eclipsed by Mendelian genetics, and in some countries compulsory sterilisation laws were imposed, the most famous of which were in Nazi Germany. It has been largely abandoned throughout the world.

Social Darwinism

For more details on this topic, see Social Darwinism.

Taking descriptive ideas as moral and social justification creates the ethical is-ought problem. When Thomas Malthus argued that population growth beyond resources was ordained by God to get humans to work productively and show restraint in getting families, this was used in the 1830s to justify workhouses and laissez-faire economics. Evolution was seen as having social implications, and Herbert Spencer's 1851 book Social Statics based ideas of human freedom and individual liberties on his Lamarckian evolutionary theory.
Darwin's theory of evolution was a matter of explanation. He thought it "absurd to talk of one animal being higher than another" and saw evolution as having no goal, but soon after the Origin was published in 1859, critics derided his description of a struggle for existence as a Malthusian justification for the English industrial capitalism of the time. The term Darwinism was used for the evolutionary ideas of others, including Spencer's "survival of the fittest" as free-market progress, and Ernst Haeckel's racist ideas of human development. Darwin did not share the racism common at that time: a point examined by the philosopher Antony Flew, who is at pains to distance Darwin's attitudes from those later attributed to him. Darwin was strongly against slavery, against "ranking the so-called races of man as distinct species", and against ill-treatment of native people.
Darwin's views on social and political issues reflected his time and social position. He thought men's eminence over women was the outcome of sexual selection, a view disputed by Antoinette Brown Blackwell in The Sexes Throughout Nature. He valued European civilisation and saw colonisation as spreading its benefits, with the sad but inevitable effect of extermination of savage peoples who did not become civilised. Darwin's theories presented this as natural, and were cited to promote policies which went against his humanitarian principles. Writers used natural selection to argue for various, often contradictory, ideologies such as laissez-faire dog-eat dog capitalism, racism, warfare, colonialism and imperialism. However, Darwin's holistic view of nature included "dependence of one being on another"; thus pacifists, socialists, liberal social reformers and anarchists such as Peter Kropotkin stressed the value of co-operation over struggle within a species. Darwin himself insisted that social policy should not simply be guided by concepts of struggle and selection in nature.
The term "Social Darwinism" was used infrequently from around the 1890s, but became popular as a derogatory term in the 1940s when used by Richard Hofstadter to attack the laissez-faire conservatism of those like William Graham Sumner who opposed reform and socialism. Since then it has been used as a term of abuse by those opposed to what they think are the moral consequences of evolution.