Sigmund Freud's influence on the 20th century is hard to overestimate. His contribution to psychology had an impact on nearly every social science and the humanities generally. In his work Totem and Taboo, Freud himself brings his insights drawn from years of psycho-analysis to anthropology. While these insights are valuable, the work is, by and large, indebted to the work of previously published anthropologists, particularly J.G. Frazer (see Totemism and Exogamy and The Golden Bough.
Freud is not completely clear about the extent to which the theories at the core of his psycho-analytic practice explain the determinants of hunter-gatherer societies. In places, he merely claims that there are analogies between the behavior of his neurotic patients and the behavior of members of communities constraint by taboos. In both instances, there is no rational explanation of these behaviors. Consequently, Freud seeks explanation in the sublimation of libidious drives in the neurotic patient and the reverence of the totem in the hunter-gatherer society.
However, Freud suggests that the incest taboo common in hunter-gatherer societies has its roots in the Oedipal Complex. Here, he makes a claim that is stronger than analogy, asserting that the mature reaction against the boy's sexual love for his mother results in a prohibition against sex with all close female relatives. Freud complicates this explanation with an account of the origin of the totem. Freud writes that the people identified with a totem are "brothers," all culpable in the murder of the "father." Given this society of brothers, it becomes taboo to mate with anyone identified with the totem, i.e., anyone within one's tribe. By this, Freud uses his psycho-sexual theory to explain exogamous marriage practices in hunter-gatherer societies.
Totem and Taboo convinced me that Freud's psycho-sexual theories -- in so far as they might be correct -- must have some influence on tribal social structures and behavior. Exactly what this influence is remains unclear to me. Totem and Taboo succeeds insofar as it shows how Freud's theories might be used in fields outside of psychology; however, I was disappointed in the detail and force of his specific arguments and disappointed by the derivative nature of his discussion of anthropology.