During the mid to late 1800s, Darwin's theory of evolution through natural selection had a major impact on social thought in the industrializing world -- the creation of the idea of Social Darwinism. The major thinker associated with Social Darwinist ideas is Herbert Spencer.
Spencer and other Social Darwinists believed that societies operate like nature does. In other words, societies are arenas for competition and "survival of the fittest" just as nature is. Therefore, whoever wins out in society -- whoever becomes wealthiest and most powerful -- has gotten to be that way because they are the most fit.
To Spencer, society should let competition continue unabated -- the government should not try to protect the weak. If government adopts this sort of a laissez faire attitude, the best people and companies will rise to the top and the society that results will be the best possible society.