In The Descent of Man (1871, 1874) Charles Darwin (1809-1882) focused special attention on the origin and history of our own species, a subject he had avoided in his previous writings on evolution. He claimed that the human animal is closest in ancestry to the two African "pongids," or anthropoid apes (chimpanzees and gorillas). Further, Darwin held that our species and these two pongids differ merely in degree rather than in kind - a controversial view that contradicted religious doctrine. The Descent of Man looks at the emergence of humans in terms of primate evolution. Darwin presents a strictly mechanistic and materialist interpretation of our species that is free from superstition and spiritualism.