Cannibalism: Sacrifice to Survival

“Survival of the fittest” is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. The concept of reproductive fitness is very well applicable in all the species of animal kingdom. Though evolution is a gradual process, the intrinsic complexity of the evolving culture in animal kingdom is very culminating to biologists and scientists. One such morbid fact about the cultures in animal kingdom is feeding on their own species for their survival, i.e. Cannibalism. The process of both killing and eating an individual of the same species, is a significant and widespread process that until recently has not received the attention it deserves. It is a major factor in the biology of many species and may influence population structure, life history, competition for mates and resources, and behaviour.

What is Cannibalism?

Cannibalism is the act of consuming an individual of the same species. It is a common ecological interaction that has been recorded in more than 1500 species. When it comes to humans, eating their own kind, it is known as anthrophagy, a practice that has been reported both, in ancient as well as in recent times. While cannibalism in other animals has always been a procedure adapted for survival or to showcase their dominance, anthrophagy, on the other hand is more of a psychological behaviour that has been either moulded due to traditional background or has developed as a psychological disorder. Cannibalism is a taxonomically widespread phenomenon observed in animal kingdom. It can be divided into two distinct behaviours; either killing and eating individuals of the same species or genera, known as cannibalistic predation or eating already dead individuals of the same species, known as cannibalistic necrophagy.

Why Cannibalism?

While cannibalism is dominantly found in the animal kingdom, it’s occurrence is based primarily on two reasons. Firstly, it may be a procedure adapted by the members of a species to control their population and to select only the fittest individuals as seen in certain species of ants. In certain ants, injured immatures are regularly consumed. When food is lacking, the colony turns to the remaining healthy immatures. This practice allows the adults to survive the food shortage and live to breed again. However, ants shall not be considered as the best example of cannibalism. Ants occasionally and very rarely perform cannibalism, specifically in situations of food scarcity. Although social insects often eat their own eggs, larvae and pupae, cannibalism against corpses of adults is considered quite rare in ants.

Secondly, it may be adapted as a mechanism to show dominance of a particular member over the other members of the group. For example, in lions, males taking over a pride may kill and eat the existing young ones. As a result of which, mothers who lose their cubs will more rapidly become impregnated by the new dominant males. In either of the cases, the species is generally not dependent on cannibalism as their survival method and rather employs it only at the time of adverse conditions.

Some species, however, may use cannibalism as a method for their survival. For example, the larvae of tiger salamanders can take two forms. While the smaller type eats aquatic invertebrates, the larger “cannibal morph” feasts on the smaller non-cannibal companions. The cannibal morphs have broader heads, wide mouths, and jutting lower jaws. Their teeth can be up to three times longer than those of a normal salamander. This practice is utilised by the salamanders in order to grow and develop efficiently as the nutrients provided by the smaller forms are quite sufficient for their growth.

Cannibalism in the animal kingdom:

While cannibalism in humans is very rarely reported and is often found to be horrifying and disturbing, the animal kingdom rather represents the same as a common phenomenon. The subsequent sections will discuss some of the most commonly reported cannibalistic practices of the kingdom:

Sexual Cannibalism in the Praying Mantis:

The animal kingdom is the only kingdom with the most exotic and bizarre methods for attracting mates and following the legacy of reproduction or love making. But, at times, the other partner may become quite aggressive. Aggressive enough, to literally eat the other partner. In case of praying mantises, sexual cannibalism has been dominantly reported. The female after mating with its male counterpart, cannibalises its mate. But, this isn’t just a selfish phenomenon, rather its more of a sacrifice done by the male. The female needs more energy than the environment can provide. So the male, in exchange for siring her offspring, sacrifices himself as a snack.

Matriphagy, or mother-eating in Stegodyphus dumicola:

The spider species Stegodyphus dumicola, native to South Africa, lives in large family groups that share both communal nests and childcare duties. The species is unique in the way that the mother crosses all the possible limits of sacrifice for their children. Once the eggs hatch, both mother as well as the virgin females show extreme length of care for their babies by producing a nourishing fluid, which they feed to their offsprings through their mouth. During this process of feeding, females gradually start to liquify their internal organs as a source of nutrition to their starving newborns. When she is almost depleted, the offsprings crawl onto their mother and start feeding on her in order to survive.

S. Dumicola is one of the species among 3% of all known species to show cooperative breeding. A practice where mated female spiders along with the virgin females, cooperatively cares for the young ones in their family and sacrifices their life for their survival.

Cannibalism in Primates:

Cannibalism in animals is surprisingly common. Although the same in primates like chimpanzees is rarely spotted except for a few times, when they have been found to be aggressive towards their own members in order to mark their dominance or in cases of food scarcity. One such incidence was reported when a family of chimps in Africa staged a purposeful attack on nearby enemies, i.e., other chimpanzees. When a few of the attackers killed a young chimp from the opposing family, they shared and ate the victim’s body. By attacking the other group, the chimpanzees protect their local food supply, and by eating the slaughtered chimp, they made sure that no meat goes to waste.

Another, surprising fact about the behaviour of female chimpanzees of a tribe is to take a maternity leave from the family at the time of giving birth. Such a behaviour is generally reported because giving birth in wild poses the new born to the risk of being cannibalised by the superior male members of the tribe. An exception to this was reported on December 2, 2014, when researchers Hitonaru Nishie and Michio Nakamura witnessed a birth in the Mahale Mountains in Tanzania. A mother delivered her new born in front of about 20 other chimps. The infant was snatched immediately after delivery and was consequently cannibalized by an adult male, a sight that led them to argue that cannibalism can be a why chimpanzee mother often leaves her group before labour begins.

Such cannibalistic behaviours in primates, however cannot be claimed to prove that these animals are cannibals. It is quite evident that the above mentioned practices are more of a conditional adaptation than a necessity for survival (as reported in Black Widow spiders and Praying mantises).

Cannibalism in humans:

Humans are the most developed and reformed organisms present on the Earth. Of all the differences that we present from other members of the kingdom, love and intelligence is the most important one. While intelligence is more of a genetic concern, love on the other hand has different definitions and reasons for it’s existence. Humans have great affection towards members of their own species and are biologically not demonstrated to be cannibalistic in nature. Some individuals or groups of individuals, however, do forecast this practice.

Some societies follow cannibalism as a cultural norm. Consumption of a person from within the same community is called endocannibalism. For example, ritual cannibalism (a type of endocannibalism) of the recently deceased was thought to be part of the grieving process where eating the flesh or internal organs of the dead will endow the cannibal with the characteristics of the deceased. This was a way of guiding the soul of the deceased into the descendants bodies. Whereas, exocannibalism is the consumption of a person from outside the community which ussually depicts a celebration of victory against a rival tribe.

The Mistaken Cannibalism:

A colony of honey bees is composed of three different groups of individuals. The Queen is the most superior of the tribe, who has the virtue of mating with the males and laying eggs. The worker bees are the most hardworking ones, who have no authority and are thus never allowed to mate. If however, they laid eggs in the tribe, the eggs will be instantly consumed by other worker bees and queen bee, and won’t be allowed to develop into younger ones. While this phenomenon itself is an example of cannibalism, lets proceed towards the bigger picture. The third group is of the males, or as the tribe calls them, drones. Drones are the male members of the tribe who mate with the queen bee, resulting to which, the queen lays eggs, which later develop into larvae and further into young and adult bees.

While the above mentioned procedure seems very regulated and simple, the details showcased by the researchers convey something else. Some of you, might have read about queen bees performing cannibalism over drones after mating. This, however is largely false, as the queens do not specifically play role in the males’ death. The death of males has been researched and found to occur due to ripping of their penis and abdominal tissues during the violent process. When a lucky drone reaches one of the queens, he mounts her and flexes his abs to extend his endophallus, the bee equivalent of a penis, into the queen’s sting chamber. He releases his semen with such speed and force that there’s said to be an audible pop. This is the climax of a male’s life—and it’s rapidly downhill from there. The drone’s endophallus stays behind with the queen, and he falls to the ground paralysed to await his end.

The havoc in the food chain:

One of the serious negative aspects of cannibalism is the occurrence of diseases associated with it. The degenerative brain disorders like Kuru and Mad cow disease have been found fatal and occurs from eating nervous tissue that is infected with either prions or some unidentified viruses. There are other diseases like scrapie, commonly found in sheep and a spongiform encephalopathy in mink which are the equivalent of diseases found in humans practicing cannibalism. When we feed the groundup entrails of these infected animals to other cattles as a protein supplement, it leads to the outbreak of Mad cow disease or kuru.

A similar type of disease almost wiped out an indigenous group in New Guinea called the Fore. The scientists on researching and analysing the scenario found that what they were seeing in the brains of these kuru victims was very similar to the effects of mad cow disease. Over the course of nearly two decades, they were able to conclude that funerary cannibalism is the most appropriate theory explaining the occurrence of these neurodegenerative disorders. Funerary cannibalism among the Fore, especially kids and women, who were involved in the preparation of the corpses and cannibalizing body parts (including the brain), was the most probable carrier for this horrible disease (a very similar practice is found in Indian cannibal cult known as Aghori). Knowing to this, certain laws were passed against eating their dead brethren, owing to which the disease was curtailed and the Fore tribe did not become extinct.

Take your call!!

Although cannibalism in animal kingdom is surprisingly common, humans have not been biologically formulated to follow the same. Animals can be cannibalistic for various reasons which may be biologically relevant to the environment of their habitat. But in case of humans, we have less of competition and plenty of food resources which refrains us from following the practice. While some tribes still follow this ritual in rememberance of their ancestral culture, other individuals are simply violating the laws of nature. A human cannibalising his own kind is no less than a murder even in case of extreme cases. This dominantly proves that necessity can never be a defence to murder.

References:

• Cannibalism: Animal behaviour
• Animal Cannibalism: Who Does It and Why
• Cannibalism—the Ultimate Taboo