Suicide & Evolution: Benefits for Animals

[Tungamirai]

Do other animals besides humans commit suicide and what is the evolutionary benefit(s) for a species that has members that commit suicide, basically what advantages does a suicidal species have over one that is not

 

[Pythagorean]

evolutionary benefit isn't always necessary to explain the existence of traits. I don't know the case for suicide, but I would start with the question "is there an evolutionary benefit?"


This article has a couple examples of animal suicide:

http://news.discovery.com/animals/animal-suicide-behavior.html

 

[Ryan_m_b]

I'm unaware of any confirmed evidence that animals do commit suicide (there are certainly apocryphal accounts) however I would warn that it is a fallacy to look at every feature and behaviour of organisms and try to explain it in evolutionary terms.

I would say that part and parcel of the complex consciousness that humans have evolved (which is a huge evolutionary advantage) is that we have the capability to commit acts that lower our fitness but this is not enough to counteract the huge increase in fitness we get as a species. Also it may not be possible to simply evolve complex behaviours such as this out of a species.

 

[Ken Natton]

I knew we had discussed something similar previously, but it took me a while to find it. The angle in this discussion was a little different, though it was based on the same basic idea of suicide having some evolutionary function. Anyway, perhaps you would like to read through this - it is quite a short thread but contains some pertinent points.

https://www.physicsforums.com/showthread.php?t=433557

 

[mishrashubham]

evolutionary benefit isn't always necessary to explain the existence of traits. I don't know the case for suicide, but I would start with the question "is there an evolutionary benefit?"This article has a couple examples of animal suicide:

http://news.discovery.com/animals/animal-suicide-behavior.html

I must confess that I am an adaptationist. I strongly believe that any trait, behavourial or otherwise, if exists stably, then it is at the very least not detrimental to the reproductive success of the organism.

It often happens, that certain evolutionary beneficial traits bring with them other harmful traits, that could be thought of as "side effects". That is to say, the genotype results in multiple phenotypes, some of them being harmful and others beneficial. However the loss in fitness is more than compensated for by the benefit. Thus there is selection in favour of the trait. A very common example is that of Sickle cell gene mutation and the resistance it provides against malaria. This can happen due to mechanisms such as Genetic Linkage, or direct effects due to mutations like in the above case of sickle cell anaemia.

So suicide in humans could be thought of as a very rare 'byproduct' of the evolution of emotions and other complex social interactions, which definitely are beneficial traits.

In other animals, such as bees or ants, the ones responsible for defence often sacrifice their lives in order protect the nest. Their death is compensated for by the proliferation of the genes that they share with the queen and other members in the nest.

 

[Ryan_m_b]

I must confess that I am an adaptationist. I strongly believe that any trait, behavourial or otherwise, if exists stably, then it is at the very least not detrimental to the reproductive success of the organism.

It often happens, that certain evolutionary beneficial traits bring with them other harmful traits, that could be thought of as "side effects". That is to say, the genotype results in multiple phenotypes, some of them being harmful and others beneficial. However the loss in fitness is more than compensated for by the benefit.

Agreed, mapping the phenome as it relates to human behaviour is a nightmare. Simplistically I see the issue of suicide this way; we have the capability to greatly model the world around us and to feel strong emotions. These are obviously helpful to our reproductive fitness but occasionally it get's to a situation where we are in a state of very negative emotion and all of our models point to the situation either not getting better or getting worse with suicide being the only way to stop feeling. Evolution is a blind watchmaker, getting rid of suicide may be possible but may not happen because it would involve a drastic alteration to our intelligence and emotional capability.

This is of course an over simplification but I think it get's my point across.

P.S. it just occurred to me that if there were individuals alive who had evolved to be incapable of suicide the only way we could know is when/if that trait spread to the whole population and we started to notice a strong psychological anti-suicide impulse in the majority of people.

 

[mishrashubham]

Agreed, mapping the phenome as it relates to human behaviour is a nightmare. Simplistically I see the issue of suicide this way; we have the capability to greatly model the world around us and to feel strong emotions. These are obviously helpful to our reproductive fitness but occasionally it get's to a situation where we are in a state of very negative emotion and all of our models point to the situation either not getting better or getting worse with suicide being the only way to stop feeling. Evolution is a blind watchmaker, getting rid of suicide may be possible but may not happen because it would involve a drastic alteration to our intelligence and emotional capability.

This is of course an over simplification but I think it get's my point across.

Precisely what I was trying to convey.

The problem with evolutionary psychology is that the formation of a hypothesis involves much more speculation than other sciences and evidence is often harder to gather. But it is an extremely interesting field nevertheless.

 

[Ken Natton]

And again, I am going to presume to throw in my lot to disagree with people whose far greater knowledge and experience I unreservedly acknowledge.

The act of suicide requires contemplation of mortality, and premeditation. Both of those are something of which only human beings are capable. Equating any animal behaviour with that is straightforwardly anthropomorphic.

 

[gkangelexa]

to make the choice to commit suicide, the animal must have a knowledge of life and death. i don't think animals have that sense or knowledge, for I think it is a philosophical sort of knowledge, and animals go by instinct, which this is not.

 

[FourierFaux]

Rodents will eat their babies. I also have trouble trying to reconcile this with any kind of evolutionary benefit.

 

[mishrashubham]

...and animals go by instinct, which this is not.

Cultural transmission is not unique to humans. Some animals such as certain primates and cetaceans, have the ability to culturally transfer behavioural patterns over generations.

 

[Pythagorean]

I must confess that I am an adaptationist. I strongly believe that any trait, behavourial or otherwise, if exists stably, then it is at the very least not detrimental to the reproductive success of the organism.

I don't disagree with the what you've said here, but I didn't think it was a question.

It often happens, that certain evolutionary beneficial traits bring with them other harmful traits, that could be thought of as "side effects".

It is not even necessary that they be harmful, just that they didn't come about because of selection. The biology community refers to them as http://en.wikipedia.org/wiki/Spandrel_(biology)" which is what I had in mind when I said that not all traits require evolutionary benefit to exist.

 

[mishrashubham]

I don't disagree with the what you've said here, but I didn't think it was a question.

That was part of my reply to the OP, not that I took what you said as a question. The quote was because I had misunderstood your statement about things not necessarily resulting from evolution.

It is not even necessary that they be harmful, just that they didn't come about because of selection. The biology community refers to them as http://en.wikipedia.org/wiki/Spandrel_(biology)" which is what I had in mind when I said that not all traits require evolutionary benefit to exist.

Thanks, the term had escaped my mind.

 

[zomgwtf]

Do other animals besides humans commit suicide and what is the evolutionary benefit(s) for a species that has members that commit suicide, basically what advantages does a suicidal species have over one that is not

Well I believe you need to define 'suicide' further.

Suicidal behaviour is exhibited in plenty of organisms (through 'altruistic' motives) and it is more than clear how these behaviours are beneficially.

Also, it sort of sounds like you're under the notion that evolution has a choice between benefit and non-benefit and it makes a selection based on that. This isn't the case though. Evolution is really just a term which indicates change.
So any change is evolution... the process pays no mind to whether or not the the change is beneficial (although by through selection beneficial changes are most probable to make it generation to generation). So 'non-beneficial' characteristics can 'piggy-back' along in organisms with mostly beneficial genes. Sometimes these originally non-beneficial genes get adapted to become beneficial, even. I can't think any off the top of my head though, pretty tired at the moment. :P

 

[girlgeek]

I'm surprised that no one has mentioned lemmings. According to mythology they all run into the sea and commit suicide.

According to wikipedia
"Actually, it is not a mass suicide but the result of their migratory behavior. Driven by strong biological urges, some species of lemmings may migrate in large groups when population density becomes too great. Lemmings can swim and may choose to cross a body of water in search of a new habitat. In such cases, many may drown if the body of water is so wide as to stretch their physical capability to the limit. "

I'm surprised that they haven't evolved into a creature with enough sense to avoid throwing themselves into bodies of water too big to swim across.

 

[Ryan_m_b]

I'm surprised that no one has mentioned lemmings. According to mythology they all run into the sea and commit suicide.

According to wikipedia
"Actually, it is not a mass suicide but the result of their migratory behavior. Driven by strong biological urges, some species of lemmings may migrate in large groups when population density becomes too great. Lemmings can swim and may choose to cross a body of water in search of a new habitat. In such cases, many may drown if the body of water is so wide as to stretch their physical capability to the limit. "

Well as you point out they aren't actually committing suicide. Birds sometimes drop out of the sky from exhaustion on long migrations.

I'm surprised that they haven't evolved into a creature with enough sense to avoid throwing themselves into bodies of water too big to swim across.

Whose they? Clearly the migration behaviour is advantageous to the species as a whole, remember that evolution is a blind watchmaker. To evolve a means of ascertaining risk at the level you're talking about as well as keeping the advantages of their behaviour is a tall order.

 

[ViewsofMars]

Clearly the migration behaviour is advantageous to the species as a whole, remember that evolution is a blind watchmaker. To evolve a means of ascertaining risk at the level you're talking about as well as keeping the advantages of their behaviour is a tall order.

I want to take a moment and help educate people. Here are two snippets from the American Association for the Advancement of Science though I highly encourage people to read the document in its entirety. It is entitled Evolution on the Front Line:

1. What is evolution?

Evolution is a broad, well-tested description of how Earth's present-day life forms arose from common ancestors reaching back to the simplest one-celled organisms almost four billion years ago. It helps explain both the similarities and the differences in the enormous number of living organisms we see around us.

By studying the sequence of changes in fossils found in successive layers of rock as well as the molecular evidence provided by modern genetics, scientists have been able to trace how ancient organisms — through a process of descent with modification — gave rise to profound changes in populations over time. Many new anatomical forms have appeared, while others have disappeared. In a very real sense, we are distant genetic cousins to all living organisms, from bacteria to whales.

Evolution occurs in populations when heritable changes are passed from one generation to the next. Genetic variation, whether through random mutations or the gene shuffling that occurs during sexual reproduction, sets the stage for evolutionary change. That change is driven by forces such as natural selection, in which organisms with advantageous traits, such as color variations in insects that cloak some of them from predators, are better enabled to survive and pass their genes on to future generations.

Ultimately, evolution explains both small-scale changes within populations and large-scale changes in which new species diverge from a common ancestor over many generations.

2. Is the science classroom the appropriate place to discuss the religious interpretations of science?

No. Religion is a subject of inquiry in historical, philosophical and social studies, not in science. So, discussion about religion is most appropriate in the social studies or humanities curriculum, not in the science curriculum.

http://www.aaas.org/news/press_room/evolution/qanda.shtml

 

[arildno]

My view is:
Evolutionary theory can legitimately be challenged to provide answers to those traits that are HIGHLY frequent/universal, but there are no reason whatsoever why weird&infrequent behaviour in any way ought to be explained by it.
Just my two cents..

 

[ViewsofMars]

My view is:
Evolutionary theory can legitimately be challenged to provide answers to those traits that are HIGHLY frequent/universal, but there are no reason whatsoever why weird&infrequent behaviour in any way ought to be explained by it.
Just my two cents..

Thanks for joining the conversation Arildno. What do you consider to be weird and infrequent behavior?

Here is an abstract from a larger document pertaining to behavior:
“Referential models based on extant African apes have dominated reconstructions of early human evolution since Darwin’s time. These models visualize fundamental human behaviors as intensifications of behaviors observed in living chimpanzees and/or gorillas (for instance, upright feeding, male dominance displays, tool use, culture, hunting, and warfare). Ardipithecus essentially falsifies such models, because extant apes are highly derived relative to our last common ancestors. Moreover, uniquely derived hominid characters, especially those of locomotion and canine reduction, appear to have emerged shortly after the hominid/chimpanzee divergence. Hence, Ardipithecus provides a new window through which to view our clade’s earliest evolution and its ecological context. Early hominids and extant apes are remarkably divergent in many cardinal characters. We can no longer rely on homologies with African apes for accounts of our origins and must turn instead to general evolutionary theory. A proposed adaptive suite for the emergence of Ardipithecus from the last common ancestor that we shared with chimpanzees accounts for these principal ape/human differences, as well as the marked demographic success and cognitive efflorescence of later Plio-Pleistocene hominids”: http://www.sciencemag.org/content/326/5949/74.abstract

As far as suicide is concerned, the Depression and Bipolar Support Alliance states, “The most important thing to remember about suicidal thoughts is that they are symptoms of a treatable illness associated with fluctuations in the body’s and brain’s chemistry. They are not character flaws or signs of personal weakness, nor are they conditions that will just "go away" on their own.” (1) Also, the Mayo Clinic states, “There may also be a genetic link to suicide. People who complete suicide or who have suicidal thoughts or behavior are more likely to have a family history of suicide. While more research is needed to fully understand a possible genetic component, it's thought that there may be a genetic link to impulsive behavior that could lead to suicide.” (2)

1. http://www.dbsalliance.org/site/PageServer?pagename=crisis_suicide_suicide

2. http://www.mayoclinic.com/health/suicide/DS01062/DSECTION=causes

3. Just located this on suicide prevention: http://www.medicine.manchester.ac.uk/mentalhealth/research/suicide/prevention/nci/inquiryannualreports/Annual_Report_July_2011.pdf

 

[Constantinos]

I thought bees were suicidal. When trying to defend their hive from animals, they sting the animals and detach the stinger, which leads to their death. Isn't this true?

 

[Ken Natton]

I thought bees were suicidal. When trying to defend their hive from animals, they sting the animals and detach the stinger, which leads to their death. Isn't this true?

No, not really. All hymenoptera have this behaviour which is what biologists mean when they use the term ‘altruism’. The bees sacrifice themselves for the greater good of the hive, and it is a behaviour that does make sense in purely Darwinian evolutionary terms, on the basis of the long term benefits of the individual bee’s genes. There are much deeper subtleties to this, the preceding is really a hopeless over simplification of the point, but for the current discussion, the point is that this is not, by any stretch of the imagination, suicide. The bees are simply engaging in a genetically programmed behaviour. They are not contemplating their own mortality and making a conscious decision to end their own life.

 

[Constantinos]

No, not really. All hymenoptera have this behaviour which is what biologists mean when they use the term ‘altruism’. The bees sacrifice themselves for the greater good of the hive, and it is a behaviour that does make sense in purely Darwinian evolutionary terms, on the basis of the long term benefits of the individual bee’s genes. There are much deeper subtleties to this, the preceding is really a hopeless over simplification of the point, but for the current discussion, the point is that this is not, by any stretch of the imagination, suicide. The bees are simply engaging in a genetically programmed behaviour. They are not contemplating their own mortality and making a conscious decision to end their own life.

Yes sorry, I missed a previous post of yours that defined suicide as such. Well then I guess no animal is capable of such a behavior. It does depend on the definition of "suicide", but I think I can agree with this particular one.

 

[Ken Natton]

Yes, I hadn’t thought about it, but I suppose this is another matter of how you interpret the terminology. When I was, some time ago, involved in a discussion on another forum about altruism, the discussion degenerated into a wholly pointless argument about the definition of the term ‘altruism’. There were a whole group of contributors who wanted to argue that there is no such thing as altruism because, ultimately, all behaviour is governed by self interest. That then led to an equally irrelevant argument about human motivation and human dignity. All of which hopelessly missed the point, of course. The behaviour in hymenoptera is real and observable. It is something that, on the surface seemed to be contrary to Darwinian evolution, but after a great deal of work by some more careful thinkers, proved to be entirely compatible with Darwinian evolution. And, where it becomes interesting is when you realize that something similar does exist in other species, including humans, although there are some significant differences in how it works. One little insight into that is to realize that, while human siblings of either sex share essentially 50% of the same genes, bee sisters share 75% of the same genes with their other sisters, but only 25% of the same genes as their brothers.

In any case, the point I was driving at was that we may have a similar difference of perception of the word ‘suicide’. If suicide is simply any action which results in the loss of one’s own life, then I suppose bee behaviour is suicide. But I would suggest that generally, when we use that term in the case of humans, we are referring to a complex cognitive chain followed by the individual that led to an action whose primary purpose was the ending of their own life. That is something of which only humans are capable.