If old-school Social Darwinists like Herbert Spencer viewed nature as a marketplace, albeit an unusually cutthroat one, the new version was outright capitalist. The neo-Darwinists assumed not just a struggle for survival, but a universe of rational calculation driven by an apparently irrational imperative to unlimited growth.

We all know the eventual answer, which the discovery of genes made possible. Animals were simply trying to maximize the propagation of their own genetic codes. Curiously, this view—which eventually came to be referred to as neo-Darwinian—was developed largely by figures who considered themselves radicals of one sort or another.

Mutual Aid grew from a series of essays written in response to Thomas Henry Huxley, a well-known Social Darwinist, and summarized the Russian understanding of the day, which was that while competition was undoubtedly one factor driving both natural and social evolution, the role of cooperation was ultimately decisive.

An alternative school of Darwinism emerged in Russia emphasizing cooperation, not competition, as the driver of evolutionary change. In 1902 this approach found a voice in a popular book, Mutual Aid: A Factor of Evolution, by naturalist and revolutionary anarchist pamphleteer Peter Kropotkin.