What's the point of cannibalism?


BBC Nature editor Matt Walker has a long meditation on the possible benefits of cannibalism, centered around two bits of newly published research. First, a recently recorded case of a female tamarin monkey killing and eating her own infant. Second, a study documenting behavior in locust swarms.

Cannibalism is emotionally disturbing, he writes, and it also seems logistically nonsensical—if you eat the opposite sex, you limit your chances of mating; if you eat your offspring, you destroy your own genes' hard work; if you eat your neighbors, your lose potential allies; and, eventually, you might encourage others to eat you. So why does cannibalism happen at all? It's a question science doesn't have a solid answer for, especially when it comes to the kind of cannibalism that involves murder, as opposed to simply eating individuals who died in other ways.

But the case of the cannibalistic monkey is especially interesting; the mother moustached tamarind, which lives in the Amazon rainforest in Peru, intentionally killed her young son, by biting and eating its head. That makes it only the third recorded case of maternal infanticide recorded in wild non-human primates.

Researchers can of course only speculate about her motivation ... They suspect the mother killed her baby because she knew it had a low chance of survival anyway. Tamarinds rely on other adults to help raise their young, and there were few of these around when the mother made her fateful decision. So the primatologists think she terminated the investment in her offspring due to the low availability of helpers. The baby was simply born at a bad time, and as tamarinds ovulate relatively quickly after giving birth, the mother, in terms of reproductive economics, made a cost effective decision. That doesn't explain why she then began to consume her young. In this instance, the mother only ate part of her infant's corpse; the head, brain and a small part of his shoulder and neck. So she didn't kill her offspring for its meat. But once dead, she probably gained some nutritional benefit by eating its brain, offsetting some of her costs in producing the baby.

But cannibalism can be about more than just individual survival ... Eating your own may be the driver behind the mass migration, and swarming, of locusts, researchers have just announced. Cannibalistic interactions have been shown before to be the driving force behind the collective mass movement of Mormon crickets and Desert locusts. The basic idea here is that locusts combine into swarms because they are frightened of being eaten by each other. But researchers have now provided the first evidence that cannibalism has an adaptive benefit for desert locusts, which form "bands" as they migrate en mass.

Australian plague locusts cannibalise other vulnerable locusts to compensate for a lack of protein in their diet. Individuals move forward to find new food, and avoid being eaten by each other, producing an advancing swarm. But the scientists, led by Matthew Hansen of the University of Sydney, Australia, also show that locusts that are given the opportunity to eat each other on average survive longer and move further. They call it the "lifeboat mechanism"; locusts actually have a better chance of surviving longer and travelling further if they all jump into a swarm together and become cannibals.

BBC Nature: Cannibalism—What is it good for?

Via John Rennie

Image: Some rights reserved by Lazurite


    1. I will definitely avoid eating people who eat Crunchy Crotch. That stuff’s only a step away from liquid plastic and I prefer higher quality meats.

  1. See? We all need to reconsider “A Modest Proposal” and this time without the satire.

  2. Country Crock takes me back. We had those big tubs all they way through High School. I use real butter now, but oh the memories.

  3. Hamsters will eat their young if they perceive a food shortage, or if their diets do not have enough protein.

    The first time my female had a litter, I had not even realized it was pregnant. It had been receiving normal amounts of food and water, but it must not have been enough: she consumed all of the babies. The next time, I increased the amount of available food, and added higher-protein snacks and dietary supplements. That litter was nursed and weaned normally, with no cannibalism.

  4. I read that spiders try to consume their newly hatched young. This benefits the species by weeding out the slow and defective. If you escape your spider mama, you are more likely to carry on mama’s genes than your slow-poke siblings.

    When the apocalypse comes (in a few weeks) I plan on setting up snares outside the local gyms, GNCs and VitaminStores. I figure that body builders have the most meat to offer, and they’re also the only creatures who can turn that powdered protein in a bucket into muscle.

    1. When the apocalypse comes (in a few weeks) I plan on setting up snares outside the local gyms, GNCs and VitaminStores. I figure that body builders have the most meat to offer, and they’re also the only creatures who can turn that powdered protein in a bucket into muscle.
      Too funny.

    2. But you’re going to end up with some pretty tough meat, full of hormones. Think organic and pampered–set up outside day spas for the Kobe beef of humans.

      1. Good point. If time allows I’ll put them on a diet of beer, and have my assistant massage them while reading Become What You Are by Alan Watts.

  5. One observation does not constitute a basis for any kind of ethological theory. The single instance of a tamarind eating its young could be due to all manner of things: It could confer a survival advantage on the mother, but it could also just be due to some freak abnormality.

  6. Heh, I was just reading about the Church of Euthanasia and then I see this article. :D Cannibalism is one of the four pillars of the church I think.

  7. The advantages of cannibalism have been studied for far longer than this article would suggest- in tiger salamanders, for instance. Tiger salamanders develop into one of two morphs, one of which is cannibalistic; it turns out that the cannibalistic morph grows and matures faster than the non-cannibalistic. The advantages are clear- as grimc points out, we are what we eat, and it makes sense to choose a diet that matches the composition of our own tissues as closely as possible.

    So why don’t more organisms perform cannibalism? Perhaps to avoid negative intraspecific interactions, or to avoid eating kin. The work on the salamanders suggests that the cannibals get more debilitating parasites. This may be true of humans as well- as nemik points out with his link to info on Kuru.

    1. I found the Beeb article a bit wishy-washy, to be honest.

      Anyway …

      There are both benefits and disadvantages to cannibalism. The most obvious benefit is the immediate and relatively easy access to large amounts of sustenance in the form of your sibs, parents and close relatives. Also, who is competing for resources in exactly the same ecological niche as you? Why, those of the same species, that’s who! I can even see that cannibalism might even be an evolutionarily stable strategy (ESS), at least in times of crisis – those who consume their nearest-and-dearest aren’t *directly* endangering their own genetic survival while ensuring that their own chance of survival is increased. If you can reproduce relatively rapidly and in sufficient numbers, there are even circumstances in which it makes sense to kill and/or consume your own offspring, because the energy input required to bring them to self-sufficiency can be allayed by their death and partial consumption, and replacements can be relatively easily produced. However, that you have such feelings of moral disgust towards such cold-heartedness simply tells you that it’s not a major part of your species’ own survival strategy …

      However, that said, there’s more to survival than just having the right genes. Those of your same species are also likely to be the ones who come to your defense in crisis – and numbers can be important when fending off predators or extraspecific competition. Also, as mentioned previously, the kinds of diseases and parasites that like to live in your relatives are probably going to thrive in you, too.

  8. Anyone who has had children understands why some animals eat their young.

    It’s not just a joke; honestly, there are times…

  9. “Hamsters will eat their young if they perceive a food shortage, or if their diets do not have enough protein.”

    I’ve seen cannibalism in domesticated rabbits. Spontaneous abortion is also fairly common. My theory is that both are triggered by overcrowding and/or food shortages, but others think it’s caused by the presence of predators or humans too soon after birth.

    1. SpellCheck doesn’t acknowledge that fact, which is probably why it’s misspelled.

    2. To be fair, a tamarind monkey would probably taste better than a tamarin monkey, at least when eaten raw…

  10. “That makes it only the third recorded case of maternal infanticide recorded in wild non-human primates. Researchers can of course only speculate about her motivation … They suspect the mother killed her baby because she knew it had a low chance of survival anyway.”

    Er, if this was only the third recorded case of maternal infanticide, maybe it was because the mother was mentally ill. Given that she “only” ate from mostly the head and ignored the rest of the body, clearly she didn’t need the nutrition. If the mother was sane, and realized the baby had a low chance of survival, she could have simply abandoned it.

  11. When I was 11 my hamster ate her babies, leaving only their little heads. Twenty years later, I was a heroin addict.

    You be the judge.

    1. I’m not sure what’s more fucked up — your anecdote, or the fact that it made me chuckle…

  12. Maybe it’s just me, but whenever we ask questions like “What’s the point of *insert naturally occuring behaviour*?” aren’t we venturing headfirst into Intelligent-Design-territory, albeit with another vocabulary?

    Evolution is all trial-and-error, it doesn’t follow a pre-drawn map. Nature doesn’t have a “point”, nature just IS.

    A more sensible way to phrase the question would be “What’s the point of cultural taboos against *insert naturally occuring behaviour*?” Because that is means to an end, something wich can be measured in terms of effectiveness.

    1. Absolutely. Our own feelings of moral disgust can tell us as much about our evolutionary past and present as they do about the nausea-inducing behaviour we are observing.

    2. A better question would simply be “what are the advantages of cannibalism to its practitioners?”, and it is that biological question that I addressed in my response. The problem is that the question as aksed could also be interpreted as “what is the social significance of cannibalism” or “why are taboos against cannibalism almost universal in human societies”; those questions need to be distinguished from the purely biological “why is it (sometimes?) advantageous to eat your own kind?”.

      As an aside, I was just reading an Aubrey-Maturin book (part of Patrick O’Brian’s Master and Commander series) wherein some castaways eat a dead crew member (or at least gnaw on him a bit). I totally get that- I would totally do the same.

  13. It’s bound to get you just the kind of nutrients you need. And it prepares you in case you wind up with an appendage in a trap.

    1. Soylent Green is people! PEEEEPLE!!!

      And economists have an answer for this behavior. It’s called high time preference.

  14. Auto-cannibalism is not the answer, as sure as talking to yourself is the first sign of impending mental collapse.

  15. I think we could legalize cannibalism as long as the cannibals promised to only consume liposuctioned fat ftw.

  16. I can’t afford name brand butter substitutes. Instead of “I can’t believe it’s not butter”, I have to buy, “If this isn’t butter, what else are they lying to me about?”

  17. hey-
    anyway to find out who the dude is in the picture?

    its a little creepy how much he and i look alike, perhaps twins separated at birth?

  18. I could swear that eating the brain/nervous system tissue of your own species is, like, really, really not so good for you. As in, prions and stuff. MAD COW DISEASE, MAN!

  19. Eating your enemies makes more sense than killing them and NOT eating them. Though using them as fertilizer would have much the same benefit, with a lower risk of disease.

  20. eating you enemy would be a good form of torture as long as you dont kill them in the prosses but it would also be disgusting and completly horrific and so horror movie and a little uncreative

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