Unwin's conclusions, which are based upon an enormous wealth of carefully sifted evidence, may be summed up as follows. All human societies are in one or another of four cultural conditions: zoistic, manistic, deistic, rationalistic. Of these societies the zoistic displays the least amount of mental and social energy, the rationalistic the most. Investigation shows that the societies exhibiting the least amount of energy are those where pre-nuptial continence is not imposed and where the opportunities for sexual indulgence after marriage are greatest. The cultural condition of a society rises in exact proportion as it imposes pre-nuptial and post-nuptial restraints upon sexual opportunity.〔Huxley, Aldous (1946). ("Ethics." ) In: ''Ends and Means.'' London: Chatto & Windus, pp. 311–12.〕

The whole of human history does not contain a single instance of a group becoming civilized unless it has been absolutely monogamous, nor is there any example of a group retaining its culture after it has adopted less rigorous customs.〔Unwin, J. D. (1927). "Monogamy as a Condition of Social Energy,” ''The Hibbert Journal,'' Vol. XXV, p. 662.〕