Final answer:
Specializing on cannibalism is unsustainable due to human digestive adaptations, the abhorrent nature of the practice to human psychology, and the inability to renew human resources in a way sustainable for populations.
Step-by-step explanation:
The reason why specializing on cannibalism is likely not sustainable is multifaceted. Firstly, cannibalism goes against the adaptations that humans have evolved for obtaining and digesting a varied diet. Our digestive systems and biochemical properties of our digestive juices are not optimized for consuming human flesh as a primary food source. This could lead to ill health if practiced extensively, as seen with animals that do not consume their adapted diet.
In addition, the practice of cannibalism is unsustainable from a social and cultural perspective. Within societies, cannibalism can undermine the fabric of trust and cooperation that binds communities together. The very psychology of human nature generally finds cannibalism abhorrent, posing significant obstacles to its practice on any large scale.
Moreover, considering sustainability from an ecological and resource management perspective, cannibalism fails to be robust. It does not offer a renewable resource in the way plant-based foods or traditional livestock do, as it would ultimately result in population decline and disrupt social order. Sustainable practices require resources that can be renewed or continuously produced without exhausting the system, which is not feasible with cannibalism.