Man Into Wolf; An Anthropological Interpretation of Sadism, Masochism and Lycanthropy is a book by Robert Eisler, published in 1948.

The text is based upon his readings in archeology and anthropology; anything not covered by these disciplines is then dealt with using Jungian methods of dream analysis and the theory of archetypes.

He asserts that humanity evolved from two groups of apes: one peaceful, vegetarian and practicing free love; the other violent, carnivorous and given to fighting over sex partners.

However, Eisler argues that Ice Age food shortages caused some to imitate wolves and other beasts of prey, wearing animal skins and taking up hunting.

Eisler advocates a return to what he imagines was the harmonious life of the earliest primates and proposes the development of a new psychology and ultimately a new society, lest we are destroyed in a nuclear war brought about by descendants of the wolf-men.