Biologiste britannique, ami de Charles Darwin, il était surnommé « Le bouledogue de Darwin ». Huxley fut convaincu par la théorie de l'évolution. Il publia en 1863 Evidence as to Man's Place in Nature (La Place de l'homme dans la nature) dans lequel il développa la thèse que les singes anthropoïdes sont nos proches parents, ce qui lui valut des critiques de la part des non-évolutionnistes
Written partly in response to Social Darwinism and in particular to Thomas H. Huxley's Nineteenth Century essay, "The Struggle for Existence", Kropotkin's book drew on his experiences in scientific expeditions in Siberia to illustrate the phenomenon of cooperation. After examining the evidence of cooperation in nonhuman animals, in pre-feudal societies and medieval cities, and in modern times, he concluded that cooperation and mutual aid are the most important factors in the evolution of species and the ability to survive.