The Cannibal Within offers an evolutionary account of the propensity of human beings, in extreme circumstances to eat other human beings, despite the strong Western taboo against such practices. What sets this volume apart from the large body of literature on cannibalism, both popular and anthropological, is the underlying premise: cannibalism as an alternative to starvation is tacitly condoned by the same biological morality that would condemn cannibalism of other sorts in non-threatening situations. Deep as the taboos may be, the survival instinct runs even deeper.

The title of the book reflects the author's belief that cannibalism is not a pathology that erupts in psychotic individuals, but is a universal adaptive strategy that is evolutionarily sound. The cannibal is within all of us, and cannibals are within all cultures, should the circumstances demand cannibalism's appearance and usage. Petrinovich's work is rich in historical detail, and rises to a level of theoretical sophistication in addressing a subject too often dealt with in sensationalist terms.

The major instances in which survival cannibalism has occurred convinced the author that there is a consistent pattern and a uniform regularity of order in which different kinds of individuals are consumed. In considering who eats whom, when, and under what circumstances, this regularity appears, and it is consistent with what would be expected on the basis of evolutionary or Darwinian theory. In short, he concludes that starvation cannibalism is not a manifestation of the chaotic, psychotic behavior of individuals who are driven to madness, but reveals underlying characteristics of evolved human beings.