Science Questions

Is it evolutionarily advantageous to be a cannibal?

Sun, 12th Sep 2010

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David Whalley asked:

Is it evolutionarily advantageous to be a cannibal?


Dave -   I guess it depends what you are and how many diseases you’ve got that are going around.  The big disadvantage to being a cannibal, evolutionarily, is that if you’re eating something of your own species, it can get all the same diseases that you can.   And therefore: you eat them and then you get all of their diseases and then you die. 

Chris -   Yeah, that’s exactly what happened to the Fore people in New Guinea who developed a disease called Kuru, which was a prion disease - a bit like Mad Cow Disease but it was a human equivalent.  And because it was a ritual for the women in the tribe to eat the brains of a dead relative when they buried them, there was an excess of women affected by this terrible neurological condition that came on all of a sudden.  The actual word means “he who trembleth” in the native language because people got this BSE-like disease and they all died.  It was first identified as a cannibalistically-transmitted tendency many years ago which means it’s interesting that people went and did almost the same experiment with cows and then were really surprised when BSE came along.  

So I would say that actually, from an evolutionary point of view, it is not advantageous to be a cannibal, at least not for humans, and so that probably explains why the practice is so rare. 

Dave -   Although I guess in some other species, especially if you’re a very small animal which is quite short-lived and disease isn’t so much of an issue, if you’re really, really hungry then cannibalism is better than dying of starvation.  So things like locusts will eat each other quite happily if they’re hungry. 

Chris -   So there you go, David Whorly 94: if you are going to be short-lived then it’s probably okay for you to be a cannibal – you may benefit from the increased nutritional benefits of eating your compatriots. Muscle has got lots of iron in it and lots of protein which will help you to build your own muscles up. But you could, if you’re going to live a long time, succumb to all kinds of nasty diseases so it will be disadvantageous.


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My understanding is that there's quite a lot of evidence in the fossil record that cannibalism went on.

The brain in particular is a good source of various nutrients like DHA.

The fact that humans don't catch BSE and scrapie very easily (unlike many other animals) seems to be evidence that humans may have done a great deal of cannibalism in the past; enough that we may have evolved to be proof against many prion diseases that it can cause. wolfekeeper, Tue, 14th Sep 2010

but, but, but, according to Flanders and Swann, "eating people's wrong"! Geezer, Tue, 14th Sep 2010

"You are what you eat", any truth to it?
In bad taste, is eating and digesting the same species, has some kind of detrimental affect?

Also; Bovine spongiform encephalopathy (BSE), commonly known as mad-cow disease.
The way it is transmitted...

"Cattle are normally herbivores. In nature, cattle eat grass. In modern industrial cattle-farming, various commercial feeds are used, which may contain ingredients including antibiotics, hormones, pesticides, fertilizers, and protein supplements. The use of meat and bone meal, produced from the ground and cooked left-overs of the slaughtering process as well as from the cadavers of sick and injured animals such as cattle, sheep, or chickens, as a protein supplement in cattle feed was widespread in Europe prior to about 1987. Worldwide, soya bean meal is the primary plant-based protein supplement fed to cattle"

tommya300, Tue, 14th Sep 2010



. tommya300, Wed, 15th Sep 2010

Wolfekeeper, BSE (cows), Scrapie (sheep), Creutfveldt-Jacob Disease (CJD and Kuru for humans), and even Mad Hamster (squirrel, deer and so on) Disease all are transferred about equally between members of the same species, and are much harder to transfer cross species.

For the general argument, I think another important evolutionary detriment to cannibalism is the fact that humans are very dangerous and difficult to kill without putting oneself in jeopardy. This is because of tool use, intelligence, and friends, family, and community that have interrelated obligations. I think that this would greatly outweigh the food factor. Steve SteveFish, Fri, 10th Dec 2010

There are many cannibalistic species.

For example the Black Widow who eats her mate.

Many fish eat smaller fish...  including their own young.

While perhaps not truly cannibalism, many mammals will eat their own afterbirth.

Creutzfeldt-Jakob Disease and Prion diseases are concentrated by a cycle....  For example, with Creutzfeldt-Jakob Disease disease, they were eating the dead within the same tribe (including those that were affected by the disease).  If they had only eaten the dead of non-cannibals, then it would have been less likely to propagate the disease.  Especially eating the non-cannibals that were killed in battle or were otherwise healthy at the time of death.

The same thing happened with Mad Cow Disease.  Feeding "meat meal" as a protein supplement.  Then butchering the animals....  and doing it over again.  Rendering plants would take the waste carcasses...  So any animal that died from disease was sent to the renderer rather than the butcher.  What better way to propagate disease than feeding essentially the diseased carcasses as a protein supplement to the healthy...  then repeating it with any that got sick.  The rendering process should have killed bacteria and viruses, but apparently missed the prions.

CliffordK, Sat, 11th Dec 2010

What about the scavenger species...

I assume they'll eat anything that isn't moving without respect to the species.

How do they protect themselves? CliffordK, Sat, 11th Dec 2010

It was Kuru that was a problem in New Guinea, although it is probably the same disease as CJD which develops spontaneously in western populations. There is probably a genetic component but it transmits readily to others. It is important to remember in this context that new Guinean's who were cannibals were mostly only eating human brains as part of a ritual, not for food.

As I already said, it is much harder to transfer prions between species so predators would have some protection, although the scavenger problem is interesting and I wonder if somebody has looked into it. On the other hand, because the cross species disease takes quite a while to develop, many predators may have already reproduced and would be pretty old before they were stricken and therefore would not have an evolutionary effect.

Prions are fascinating because they are just membrane proteins that are found in most mammals in slightly different forms. The abnormal protein is folded incorrectly such that it can bind to other normal proteins and force them into the abnormal conformation. This builds up a large rigid structure that kills neurons, and it is so tough that it has to be heated to above 460 degrees (Fahrenheit I think) to be denatured. Sterilized surgical instruments used in brain surgery have transmitted the disease to other patients.

I think that the prion structure should be studied as a model for how to proceed with research that would substitute proteins for other tough materials that are used in manufacturing. SteveFish, Sat, 11th Dec 2010

If there are any evolutionary processes involved, I think it is not in favor of cannabilism.

I was going to state some fancy things like Creutzfeldt-Jakob Disease and kuru, but I see that's been done! :) Such diseases seem to be natures way of telling us not to! QuantumClue, Sun, 19th Dec 2010

I think that this disease probably has a relatively small evolutionary potential and it is a major mistake to personalize mother nature. There are quite a number of pseudo random events in evolution that don't require an adaptational explanation. Prions are very likely one of those accidental happenings that is an emergent property of complexity that have directly made a few individuals very miserable, but the knowledge gained from understanding them can benefit many. SteveFish, Sun, 19th Dec 2010

It's not a matter of personalizing mother nature. She states the facts as it is. QuantumClue, Sun, 26th Dec 2010

There was no statement of facts, certainly not to the New Guineans who were just going about their lives and rituals. There was no way for these folks to connect what they did with a disease that took years to develop. It was western science that figured out what the practice and agent that caused their disease was, and when informed they stopped. SteveFish, Sun, 26th Dec 2010

My original point was that ''she'' that is, mother nature must have decided at one point, for a better word, that consumption of like beings was not acceptable. Hence why sporadic diseases appeared, because we were not supposed to consume our own. QuantumClue, Mon, 27th Dec 2010

The mother nature notion is magical thinking. SteveFish, Mon, 27th Dec 2010


QC may be using the term "mother nature" as a metaphor. I don't think he indends us to take it literally. Geezer, Mon, 27th Dec 2010

Geezer, he may be using mother nature as a metaphor, but it is a bad one. He says "Hence why sporadic diseases appeared, because we were not supposed to consume our own" and this implies intention. This is one of the big mistakes many make regarding evolution or ecological imperatives. There is no one but ourselves to suppose that we shouldn't consume our own, and evolution does not work toward any particular outcome. I would like to know what we are supposed to do to avoid Huntington's chorea or Alzheimer's disease that we can learn from nature. Steve SteveFish, Mon, 27th Dec 2010


I see what you mean by "intention" and I agree with you about that. I still don't think that was what QC really meant.

Of course, it's always possible that we may never find out. Your reply might have over-torqued QC to the point that he could now care less. Was that your ambition? Geezer, Mon, 27th Dec 2010

"Was that your ambition?"

Geezer, I have no intention whatsoever regarding what QuantumQue does with his life, but I do care very much about science and the accurate dissemination of science. If QuantumQue agrees with me that would be great, but I would still caution him regarding language that appears to personalize impersonal processes. This type of language has led to all kinds of misunderstandings regarding how nature works, especially evolutionary theory. There are people out there who actually think that evolution is goal directed and works to produce the highest form of life, which they believe of course, is us. Steve SteveFish, Tue, 28th Dec 2010

Indeed they do. However, is that what QC actually meant? I don't think so. Do you? Geezer, Tue, 28th Dec 2010

I can't answer your question accurately and I have no information that would allow me to speculate. In general I prefer to stick to what people actually do or say and respond to that, it is more honest. SteveFish, Tue, 28th Dec 2010

No, mother nature is not an intellect, as a decision making machine. When I say this was mother natures way of telling us not to consume each other, I mean this in the sense, that nature has chosen? 1) a certain path where the biological nature does not entertain this way of life. The idiom mother nature is nothing more than a label many use today, and as Geezer said, I hope no one has misread this to mean that I somehow believe that nature is a decision making machine similar to human beings, or with some kind of intellectual personification.

1) Its very hard not to run into language which can be misread badly. QuantumClue, Tue, 28th Dec 2010

I think cannibalism may be a result of where you live in some cases :)
What nourishments you can get so to speak.

Also its a 'spiritual thing' in some society's.
Mostly its a waste of human life though.

I can recommend "Diamond, Jared - Guns, Germs and Steel" for an interesting reading. yor_on, Tue, 28th Dec 2010

Here's a disturbing video of someone suffering kuru QuantumClue, Tue, 28th Dec 2010

CJD QuantumClue, Tue, 28th Dec 2010

I posted some links... how come they haven't shown up? Do they need to be looked at first? QuantumClue, Tue, 28th Dec 2010

Don 't think so, you should just need to copy & paste them? yor_on, Tue, 28th Dec 2010

Disturbing. QuantumClue, Tue, 28th Dec 2010

Cannibalism for food is rare, except in some notorious emergency situations. There is some anthropology research that suggests that it might have been more widespread in the past. The New Guineans ate some of the brain in a funeral rite, and the brain is the primary source of prions. So, if there is any path that has been "chosen" by nature, it is that a tenderloin, or a liver with some fava beans and a nice Chianti are just fine, but don't eat the brains. Cannibalism is not at all unusual in other animals, even primates. SteveFish, Tue, 28th Dec 2010

Interestingly however, the form of disease does take hold in the animal kindgom QuantumClue, Tue, 28th Dec 2010

Also there was a case where people from kentucky developed the disease from eating squirrel brains. QuantumClue, Tue, 28th Dec 2010

Yes, brains are potentially dangerous, although the cross species infection rate is pretty low. We humans made it much worse for the cows, especially in the UK where being a renderer used to be a cottage business. Carcasses of what in the US are called downer cows or sheep (alive, but so sick that it can't stand up) and other dead animals, including road kill, were rendered for fat by cooking at high heat. The remaining crumbles of protein were also sold to manufacturers of, mostly, cow chow. The thing about prions is that just normal cooking doesn't affect them, they have to be heated to above 460F (240C) to break down, so the soluble prions stuck to and were concentrated in the protein crumbles.

In the US, downer cows were not rendered, but were made into pet food, but I found out a while back that until recently, veterinarians here got rid of euthanized animals by selling them to renderers. So, your fluffy and spot who you had to have "put down" may have been rendered and fed to some other critter.

The thing about prions is that they are a normal protein found in most mammals that very occasionally takes on an abnormal conformation that, in turn, causes more of the normal ones to change to the bad form. There are some genetic mutations that make this more likely to happen.

However, consider this-- a prion is a self assembling very tough and heat resistant protein. If this idea is developed it might lead to a new type of plastic like material not dependent on fossil fuels. SteveFish, Tue, 28th Dec 2010

I came across a very worrying article: QuantumClue, Tue, 28th Dec 2010

The disease is very unfortunate for the few people who get it, but the Guardian article predicted only 13 cases a year over the next 20 years. SteveFish, Tue, 28th Dec 2010

So if you are a survivor of a plane crash in the Andes mountains...

Avoid eating the brains of all the British travelers  CliffordK, Tue, 28th Dec 2010

How bizarre... when steve mentioned in the most extreme cases, the Crash of the Andes did come to mind. However, I do not believe they consumed the brains. They ate parts of the leg if memory serves. QuantumClue, Tue, 28th Dec 2010

I did know someone who claimed to have eaten sheeps brains on more than one occasion, on a seperate note. QuantumClue, Tue, 28th Dec 2010

Did you watch the movie "Alive", or read the book?

It has been about 25 years since I read it, but I thought in the book they did discuss eating the brains...  I think they described it as a desert, and somewhat like cheese.

They also ate their toothpaste...  which was like candy.
CliffordK, Tue, 28th Dec 2010

I've read the book. Was that not them trying to justify eating brains? I don't believe they went as far as that surely? Reports and even interviews of the survivors speak of resorting to eating the flesh of the dead bodies... QuantumClue, Tue, 28th Dec 2010

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