Who is considered the most influential social Darwinist advocating for the marketplace application of natural selection?

Herbert Spencer is recognized as the most influential social Darwinist who applied the concept of natural selection to societal and economic contexts. He introduced the phrase "survival of the fittest," which he used to explain the competition among individuals and groups in society as analogous to the processes of evolution in nature. Spencer advocated for minimal government intervention in the economy and believed that social progress resulted from the struggle of individuals competing for resources. His ideas shaped the understanding of economics and society in the late 19th century, suggesting that societal improvement arises through competition and that the successful are those best adapted to their social environment. This perspective reinforced existing class structures and justified laissez-faire policies during a time of rapid industrialization and social change.