In the cosmology recorded by the French anthropologist Marcel Griaule from conversations with the elder Ogotemmeli, published as Dieu d'eau in 1948, the creator god Amma shapes the earth itself as a living, gendered body, and from his union with it generates the Nommo, a set of ancestral spirits most often described as twin beings, amphibious and serpent-like or fish-tailed in form, associated closely with water, fertility, and the ordering power of speech. The Nommo are said to descend from the sky to the earth in an ark together with the eight ancestors of the Dogon clans, bringing with them the technologies and social knowledge, including weaving, agriculture, and articulate language, that make organized human life possible.
In Griaule's account, elaborated further in his later collaborative work with Germaine Dieterlen, the Nommo and the act of their descent are bound up with an origin account for speech and social order that recurs throughout Dogon ritual, mask performance, and the symbolic layout of Dogon villages and granaries, which are described as reflecting the Nommo's cosmic anatomy in their physical construction. Within this framework, the Nommo function less as objects of individual worship than as the conceptual foundation underlying most areas of Dogon cosmological and social life as Griaule and Dieterlen described it.