Convinced that primitive man had not developed the intellectual to form even such simplistic explanations as Tylor proposed, Marett also criticized E. B. Tylor’s theories of animism, suggesting that early religion was more emotional and intuitional in origin. He believed that early man recognized some inanimate objects because of their specific characteristics; treated all animate objects as having a life, but never distinguished soul as separate from the body. Considering that early man's universal belief in mana is so self-evident, Marett found insignificant the question of how men and women developed the belief that a spirit or soul resides in all objects.

He worked on the palaeolithic site of La Cotte de St Brelade from 1910 - 1914, recovering some hominid teeth and other remains of habitation by Neanderthal man. He published "The Site, Fauna, and Industry of La Cotte de St. Brelade, Jersey" (Archaeologia LXVII, 1916).

He became Rector of Exeter College, Oxford.

His students included Marius Barbeau.

He was the only son of Sir Robert Pipon Marett, poet and Bailiff of Jersey, and Julia Anne Marett.

Works and Lectures

• The Threshold of Religion, (1909)
• Anthropology, (1912)
• Psychology and Folklore, (1920)
• Faith, Hope and Charity in Primitive Religion, (1930–1932)
• Sacraments of Simple Folk, (1930–1932)
• A Jerseyman at Oxford, (1941) autobiography