Historians know that Darwin was influenced by the political economist Thomas Malthus and that natural selection was therefore compatible with Whig industrial politics, but Political Descent shows that the earlier Lamarckian ideas that were popular among radicals persisted throughout the nineteenth century both alongside and in opposition to various forms of Malthusian Darwinism. After 1832 English radicalism split along class lines; Whig radicals embraced Malthus in justification of competitive individualism whereas working class radicals favoured anti-Malthusian and Lamarckian evolutionary ideas. Thus there were two traditions of evolutionary political thought in nineteenth-century England. Political Descent traces their respective development up to the First World War. Although many Whigs interpreted natural selection as an endorsement of economic competition, the outspoken Lamarckian Herbert Spencer remained ambivalent about Malthus. Rather than endorsing individualism, in Descent of Man Darwin explained the evolution of genuinely other-regarding morals through both inter-group and intra group selective pressures. This was indicative of a broader move away from laissez-faire to a collectivist ‘new liberalism’, Thomas Huxley debated this issue with Spencer. While liberals embraced collective solutions to the social consequences of industrialisation, others drew socialist conclusions, prompting the socialist revival of the 1880s and 1890s. Political Descent charts diverse liberal and socialist politics that were variously built around Malthusian or anti-Malthusian interpretations of evolution, culminating in a consideration of the problems that August Weismann's work on heredity raised for the Lamarckian aspirations of many socialists. Further, Weismann's theory of ‘panmixia’ exacerbated late-nineteenth and early twentieth-century concerns about evolutionary degeneration.