Answer to Question #97554 in Evolution for Kate

Question #97554
Why would cannibalism be favored by natural selection?
Expert's answer

Cannibalism and Natural Selection


Also known as anthropophagy, cannibalism is a term that describes an occurrence where a member of a certain species eats another member of the same species. For instance, when a crocodile feeds on another crocodile or when a hyena feasts on the flesh of another hyena or even when a human makes a meal out of the flesh of another human being that is cannibalism of anthropophagy. Natural selection on the other hand refers to the process that leads to the adaptation of an organism to its environment through changes of the organism’s genetic composition. Through natural selection, the genotype that confers an organism the best ability to survive and thrive in its environment is preserved and multiplied from one generation to another while the weaker genes are eliminated.

While cannibalism in humans is considered a taboo, it appears to be the norm in the animal kingdom. Many animals, from bears to rabbits to salamanders and spiders and even closer home to chicken are known to eat members of their own species. But why do they do this? Why would a rabbit or a hippo which mostly feeds on plants decide to feed on their own species? There must be some benefits otherwise the habit would have stopped ages ago (Klug & Bonsall, 2019).

Granted, cannibalism stands as a violation of normal behavior where an organism preys on another organism from a different species. Be that as it may, natural selection favors cannibalism. The main goal of natural selection is to make sure that the best organism, with regard to its ability to survive and thrive, continues to reproduce and pass its abilities to its offspring and the weak organisms die. Many animals normally over-reproduce to increase the chances of survival of the young because of dangers from predators and harsh environment (Pruitt et al., 2017).  Cannibalism therefore ensures that the weak animals are eliminated from the many and hence the strong animals survive which then multiply their genes many times. Hamsters are good examples of animals that kill their young if they are born weak. This ensures that only those hamsters that are strong survive.

The other reason for cannibalism is that through filial cannibalism, organisms put evolutionary pressure on the offspring to develop quicker (Parsons et al., 2013). The world out there is tough and resources are never sufficient. Therefore, offspring that develop faster increase their chances of survival. Some animals like the baboons which live in social groups may kill young ones of other baboons within the group to eliminate competition in order to increase chances of their offspring to survive (Samuel, 2012). In so doing, the weaker genes are eliminated leaving the superior genes. In a brood of offspring, some develop faster and others take time to mature. Cannibalism ensures that those that take time to mature are removed and in so doing, the genes of such animals are eliminated. Cannibalism therefore, is one way in which natural selection ensures only the fittest organisms survive.


  • Klug, H., & Bonsall, M. B. (2019). Coevolution influences the evolution of filial cannibalism, offspring abandonment and parental care. Proceedings of the Royal Society B286(1909), 20191419.
  • Parsons, W., Zhong, W., & Rudolf, V. H. (2013). Mating status and kin recognition influence the strength of cannibalism. Animal behaviour85(2), 365-369.
  • Pruitt, J. N., Goodnight, C. J., & Riechert, S. E. (2017). Intense group selection selects for ideal group compositions, but selection within groups maintains them. Animal behaviour124, 15-24.
  • Samuel, K. (2012). Reproductive competition and cooperation among female yellow baboons. Social behavior of female vertebrates, 349.

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