In his An Essay on the Inequality of the Human Races, published in 1855, Gobineau ultimately accepts the prevailing Christian doctrine that all human beings shared the common ancestors Adam and Eve (monogenism as opposed to polygenism). He suggests, however, that "nothing proves that at the first redaction of the Adamite genealogies the colored races were considered as forming part of the species"; and, "We may conclude that the power of producing fertile offspring is among the marks of a distinct species.