[thedoc (OP)]

Is it evolutionarily advantageous to be a cannibal?
Asked by David Whalley


                                        

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[thedoc (OP)]

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, DavidWorley94: 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.

[wolfekeeper]

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.

[Geezer]

but, but, but, according to Flanders and Swann, "eating people's wrong"!

[tommya300]

"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...
http://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy

"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.[3] Worldwide, soya bean meal is the primary plant-based protein supplement fed to cattle"

http://www.eatwild.com/foodsafety.html

http://people.ku.edu/~jbrown/madcow.html

http://www.as.ua.edu/ant/bindon/ant570/Papers/McGrath/McGrath.htm

[tommya300]

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[thedoc (OP)]

We discussed this question on our  show
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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[SteveFish]

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

[CliffordK]

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]

What about the scavenger species...
Canines...
Buzzards...

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

How do they protect themselves?

[SteveFish]

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.

[QuantumClue]

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!

[SteveFish]

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.

[QuantumClue]

It's not a matter of personalizing mother nature. She states the facts as it is.

[SteveFish]

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.

[QuantumClue]

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.

[SteveFish]

The mother nature notion is magical thinking.

[Geezer]

Steve,

QC may be using the term "mother nature" as a metaphor. I don't think he indends us to take it literally.

[SteveFish]

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

[Geezer]

Steve,

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?