Interesting question! War would be adaptive if it leaves those who participate in war with more descendants than those who don't. The answer will, off course, depend on the type of war (a nuclear war would not be adaptive for anyone involved) and whether your tribe/country wins or loses.

Two scenarios where war can be adaptive are:

(i) In a (modern) society where war-veterans are considered more attractive to fertile females than those who didn't participate in war. Here participating in war can be adaptive, if the risk of getting killed or injured is low.

(ii) In a war situation where male soldiers take possession of the females of the opponent. Until recently, this happened a lot in New Guinea: men of the losing tribe were killed, and the females were incorporated in the population of the winning tribe. Here war can definitely be adaptive.

Definitely not, every war has an economic origin

Sorry, but I don't understand the sense of your answer. Just because war is a means to acquire and monopolize resources, it should be adaptive.

To be adaptative, it has to be based on heritable traits that get passed through selection for that phenomenon.

I don't see how "war" is something like an adaptation. Aggressiveness, maybe. Greed? Possibly. But war seems too complex for this.

I'm not sure, but I think that Pinker have something about this on his new book.

Thank you Fabio. My question, in its apparent simplicity, hides in fact a broad array of complex arguments and sub-arguments I would like to develop with other people. About the eredity of this "bad behaviour", I can say, citing M.R. Davie (1931), that from 1946 b.c. till 1861 d.c. we had 227 years of peace and 3357 years of war ! And how forget that different ancient homo species were cannibals?.

HIstorically speaking I believe "organized" wars were a byproduct of agriculture. Only with stored food (and consequent accumulated richness) mankind could assemble and maintain armys. In such context I would tend to believe that human aggressive behavior is adaptive, but its social organization (including armys and court backstage conspiracies) are rather cultural.

Thanks Aleks & Luciano for your interesting suggestion. As I supposed from long time, recent researches suggest that men’s tendency to engage in coalitional aggression (e.g., raids, rapes, guerrilla warfare and war) is manifest in all cultures, modern and traditional, and is therefore considered a human universal. Regarding the role of agriculture and hence sedentariness, I believe that storaging of resources and hence the possibility to arm a regular army only increased the quantitative level of aggression, resulting in true wars. But, intergroup conflicts probably dated back at least from our primate ancestors, since also chimps make war. The astonishing thing is rather our "cruelty", in this sense, we may speake about humans as "the ferociuos apes".

@Paolo: Would your assumption be that there would be no war in a matriarchal society? I hardly believe that. I see war (as others in this forum), as a struggle about resources, especially scarcity of resources may trigger war. However, I agree that the storage of resources is not needed to make war.

See the attached article. E.g. the Mundurucú example (page 20) is very interesting in this case. It shows that someone can fight because of scarcity of resources in reality, and not even realize it. I think this is still true in modern wars.

http://141.213.232.243/bitstream/2027.42/44491/1/10745_2005_Article_BF01531215.pdf

Napoleon Chagnon has a new book coming out in January "The Noble Savage" that will be of interest. I was a bit disappointed in the recent special issue of Science http://scim.ag/hum_conflict.

Flinn, M.V., Ponzi, D., & Muehlenbein, M.P. (2012). Hormonal mechanisms for regulation of aggression in human coalitions. Human Nature, 22(1), 68-88. DOI 10.1007/s12110-012-9135-y

Flinn, M.V., Geary, D.C. & Ward, C.V. (2005). Ecological dominance, social competition, and coalitionary arms races: Why humans evolved extraordinary intelligence. Evolution and Human Behavior, 26(1), 10-46.

Thank you to both Lucas & Mark. I have a lot to read this week!

Lucas is not my assumption, is the male-warrior hip. , which, admittedly, seems to me quite robust. War is a gender activity depending on sexual roles. Then, females are less prone to coalitional violence than males, and a matriarchal human society would have produced less wars. But, sincerely, how many convincing proofs that true matriarchal societies ever existed in the past?

@Paolo:

Just that females are not fighting in a majority of the wars (historically speaking) doesn´t mean that they are not part of a war, part of the unconsciousness decision to start a war, because e.g. resources are low. However, this is hard to test anyway and I admit that I´m not sure about the gender-specific roles. The very active and aggressive male role in wars might cover up some female role... For example, I would argue that e.g. a military uniform increases attractiveness of a male human, which might indirectly increase the number of males in the military.

The central question is who adapts: the individual or population. War is not a decision of the population, is a decision of the so-called "leaders". You know some example of war that has been decided by vote? i.e.an imoprtanmt part of the population?

last examples: Invasion to Irak, Afganisthan, Vietnam, Kora were voted by the USA citizen??

by the way.... this decision is a heritable trait? (see fabio comment)

I'm failing to see how all of these relates to the initial question. Even though something is based on adaptations, we cannot say it is adaptative. One obvious example is mathematics which is based on a large brain (which is though to be an adaptation for a number of things). Or music, or more specifically, Reggae.

I do not doubt that war can have an evolutionary history, but I would ask if it is an adaptation, or an epiphenomenom?

As I stated, I cannot see it as adaptation because I cannot see how it (and by "it" I refer to "complex organized war") would pass through generations. I think these line of reasoning was used by Wilson in his latest book, but was largely criticized for ignoring the sociology of war, and after-war events.

I think a similar issue is discussed in regards to religion. It is though to be either an adaptation by itself (and, again, I think Wilson argues this) or it an epiphenomenon based on adaptations or other characteristics of our primate brain.

I think that discussions of "true altruism" (in contrast to kin-selecton altruism) goes in the same direction.

@Marcelo, sorry, we are not discussing about modern wars (XXth century), we are speaking about the evolutionary basis of human coalitional violence against outgroup members. Please, take away any ideological analysis of war and focus on its biological meaning, if any.

@Fabio, sorry , I disagree with your opinion that "war" (i.e. forming men coalitions to attack other groups in order to acquire "reproductive" resources) did not pass through generations. I don't think that the victory in the second world war did not strongly favour the USA citizens. Consider this reasoning, reported from Melissa McDonald and colleagues (2012): "The logic underlying the evolution of male coalitional aggression is nicely captured in the risk contract theory of warfare (...) In lethal intergroup conflicts, the marginal gains to a group’s average reproductive success will be much lower for each additional male survivor compared with each additional female survivor, owing to the biology of reproduction (e.g. one male can impregnate 10 females). Male deaths are therefore less detrimental to the average success of the group than female deaths. So, although the potential costs are quite high for males who join a coalition, because existing and acquired reproductive resources would be reallocated among the male survivors, the benefits bestowed upon victorious males could be immense."

Then, I may argue, were only these victorious men, who passed their genes in the next generations, and this "bad behaviour" was evolutionary maintained in human populations. Clearly, today, under the scenario of a nuclear conflict, the war is totally maladaptive. But, if scenario will change, the war might still be adaptive.

@Lucas, This may be a new interesting argument: if a military uniform (either ancient and modern) increases attractiveness of a male human, it might indirectly increase number of males in the military, SINCE, I argue, it increases directly the number of female partners of such males. If this is true (in the past was surely true, I think), these men may have a higher fitness gain compared to civilians, and war propension may spread trhough the male population. Surely, all behaviors stemm from an intricate interplay between heredity and environment , and the cultural drives are as important as the philogenetical ones in mankind.

Paolo, I did not argue that. I specifically stated that I was referring to modern warfare, and not war simply as 'forming men coalitions to attack other groups in order to acquire "reproductive" resources'. That I agree that might have adaptative value.

I don't think that the bridge between the two concepts is that straightforward, but I would gladly read any paper on the topic if you provide a full reference.

@fabio: see http://rstb.royalsocietypublishing.org/content/367/1589/670.short

and also

William H. Durham ,Human Ecology, Vol. 4, No. 2, 1976

The Adaptive Significance of Cultural Behavior

Flinn, M.V., Geary, D.C. & Ward, C.V. (2005). Ecological dominance, social competition, and coalitionary arms races: Why humans evolved extraordinary intelligence. Evolution and Human Behavior, 26(1), 10-46.

Thanks!

The suggestion of a military uniform as a signal is an alluring idea (indeed).

There might be another approach taking women and Marcelo's objection of the concerned population into account (but in a different direction than Marcelo suggest) mentioned before by Fabio: According to infamous E.O.Wilson, war might not only be adaptive for men. Here is an excerpt from his recent work:

http://discovermagazine.com/2012/jun/07-is-war-inevitable-by-e-o-wilson#.UMBYm4Zk7as

He hypothesized that group-versus-group competition might be a driving force for the adaptive value of war. This would implicitly include females as beneficiaries as well, if one comprises the female tribe members of a war winning tribe. (Of course, group selection IS a controversial topic. But that is a different issue.)

Depends on the point of view, if you see it as a population of organisms, yes, the effect of war is an adaptive phenomenon of populations.

Because in other organisms, the permanence of a resource (genetic or not) for survival of this population is crucial.

Allowing arms war becomes an adaptation of the population, not the individuals who compose it. So the adaptation view from a vision in which are embedded the different economic systems, it becomes critical to the permanence of the system itself, in this case capitalism or big companies.

  It is not worth it to happen but it explains a biological view.

@Massa, sorry, but I did not understand exactly your reasoning. I am not very convinced of the "group-benefit" of the war. In other words, I don't believe in the "heroe's sacrifice" for the welfare of its own population or group, unless it was composed by many relatives, which might apply only to hunters-gatherer societies . In my opinion, warfare may remain an individual adaptation until survivors of a victorious army are allowed to sack towns and rape females of the defeated enemy.

Let's do a thought experiment varying the size of the embattled populations. First we need to determine at what point fighting can be accurately described with the word 'war.' If we allow things like turf wars between gangs, I would also like to put forward a question to any anthropologists out there: I have heard that chimpanzees organize war bands; in your professional opinion, is this a case of stretching a metaphor too far, or a genuine example of nonhuman war? Armed with these examples, the question to be addressed is, What benefits are achieved by the population and individuals that other means can't achieve?

Aside from the obvious answer, resources, one benefit is an increase of group cohesion. This raises the question, why would it be adaptive for separate demes in a species to be in conflict rather than existing in harmony? This is where my imagination fails me. Another question for anthropologists: I know bonobos organize hunting parties, but do different bonobo populations war with each other?

Interesting question! War would be adaptive if it leaves those who participate in war with more descendants than those who don't. The answer will, off course, depend on the type of war (a nuclear war would not be adaptive for anyone involved) and whether your tribe/country wins or loses.

Two scenarios where war can be adaptive are:

(i) In a (modern) society where war-veterans are considered more attractive to fertile females than those who didn't participate in war. Here participating in war can be adaptive, if the risk of getting killed or injured is low.

(ii) In a war situation where male soldiers take possession of the females of the opponent. Until recently, this happened a lot in New Guinea: men of the losing tribe were killed, and the females were incorporated in the population of the winning tribe. Here war can definitely be adaptive.

Thank you George, I completely agree with you

To add to this interesting question, it is true that chimpanzees have male coalitions who take part in territory border control, and that there are recorded examples of conflict between chimpanzee groups, even resulting in the complete disappearance of a group (see Tree of Origin - What primate behaviour can tell us about human social evolution by de Waal and others). But it is important to remember that chimpanzees have a pattern of dispersal which results in related males and unrelated females (for adults) within a group. With such group dynamics, it is easy to imagine that from an evolutionary point of view, a strong alliance of close male chimpanzee relatives have much to gain by competing for as much territory as possible (because, to be very brief, more territory = new females), and so engaging in inter-group conflict could be described as an adaptive behaviour.

It is unknown, however, what the ancestral dispersal pattern of humans is, if we look at the present distribution, there is a big majority of patrilocal societies, a significant amount of matrilocal societies (although for many societies it is common to relocate to the husband's village after a trial period and/or a certain number of children being born), quite a lot of bilocal societies (so where there is both, and not really a predominant pattern), and some duolocal societies too (where the norm is to marry within a village so neither gender disperses). Different patterns of dispersal (and so, relatedness) would affect how adaptive inter-group conflict vs inter-group alliances, or a mix of both, would be in early humans.

"@Marcelo, sorry, we are not discussing about modern wars (XXth century), we are speaking about the evolutionary basis of human coalitional violence against outgroup members."

If this is so, Paolo, why You have used the term "war"? Supposedly as the only good reason for discussing such themes are wars between human states and/or human alliances of the last few thousand years. Many remarks in this discussion demonstrate this fact. And we all know that these wars were (and are) completely different from any conflicts between groups of neandertals or less related relatives of modern humans. And if we evaluate the faster and faster changing characters of wars in the last centuries, we could only conclude that humans will never have time to evolutionally adapt to war.

Thus, as Marcelo has already said, wars have an economic origin. This is not a question of evolutionary biology.

@Veiko

I disagree with you, when you are saying "these wars were (and are) completely different from any conflicts between groups of neandertals or less related relatives of modern humans". What makes them "completely different"? I would say that (biologically speaking) the agonistic behavior against other tribes/groups/nations is an evolved behavior and therefore has also an adaptive value (at least originally - can´t say modern wars have to have it).

Also about "economic origin": Fights of groups of Neanderthals over resources had also an "economic origin"; it is not important if the "economic value" is directly food, land or our modern and abstract, but still valuable, currency.

Lukas, You make the mistake of "inclusive definition", i.e. "as there are SOME similarities between antagonistic behaviors between social institutions of modern humans and conflicts between groups of neandertals, we could easily put both types of phenomena into one pot named WAR".

Yes, You are right, both things are not COMPLETELY different, but VERY different (However, we know very few about conflicts between neanderthals). So, it is not serious to suggest that historical wars (i.e. such between social institutions of modern humans) has anything to do with adaptive behaviors.

@veiko, thank you for your contribute, but, sorry, I disagree with you. You may name the same thing as war, warfare, guerrilla, coalitional aggression and so on, but the essence of the facts does not change in principle, and all of them have surely an evolutionary biological basis. As I said above: " I believe that storaging of resources and hence the possibility to arm a regular army only increased the quantitative level of aggression, resulting in true wars", but qualitatively I don't see any difference between past and modern "wars". Of course, cultural evolution brought humans to disguise the war with many ideological reasons (e.g. religion), but the ultimate reasons are now and always economic. Finally, I contest your claim that "humans will never have time to evolutionally adapt to war". Coalitional aggression dates probably from our homo erectus ancestors (2 m.y.a. more or less) and the first tools they built up were arms to hunt prey and defend themselves against other predators (including humans, sadly), not utensils. But this true fact is too often concealed and we prefer to think we are living in the best possible world just to cite Candide.

@Mirtille, thank you very much for your contribute. From an human evolutionary point of view, the dispersal argument you introduced is crucial to this discussion. Unfortunately, we could not date back to the original dispersal pattern of our ancient ancestors by observing the present patterns of modern societies (including still surviving primitive societies).

@Paul, I know that many people rest in the overoptimistic Rousseau's utopy of the ancient man as a "bon sauvage", but, unfortunately, our ancestors (as far as homo ergaster/erectus till homo antecessor) and cousins killed and ate other humans as documented by fossil remains. Certainly, for a short period and in a very limited range, sapiens and neanderthaI inter-bred, but this might be occurred trhough raids and rapes, as usually occurs in all wars. I never said that survival is based on conflict and war, but, following Darwin ideas, in order to survive and pass my genes in the next generation I have to inevitably face competition for resources with my conspecifics. Sometimes (very often as judged by the mankind History), this competition resulted and results in war. That's all. Any ethic or moral vision should be taken away from an evolutionary ( biological) discussion of the war, in my opinion.

I agree with Dr. George Sangster's opinion and would like to add to it...

(iii) People do fight for natural resources, just like it happens in other animals. Sometimes, wars are sparked by drought and desertification. Under some situation, the male soldiers not only try to overpower the population that possesses the wealth (e.g. mineral wealth) but also try to destroy the reproductive capacity of the losing population (violence on women in all age groups), if not kill them. This happens a lot in Africa on Congolese populations. Thus, wars can be adaptive.

I agree with dear Dola and George.

Dear Paolo,

War could be thought of as an adaptation in the sense that the conquering peoples gained new knowledge's, foods, and technology in order to move up the food chain. By gaining advantages in this light would be adaptive for the purpose of spreading the population of early humans around the globe. Beginning communication regarding new information on how others lived in other places and incorporating those into their own community. Thus spreading and improving early humankind to survive and grow.

Douglas

I suggest you read my topic paper posted on this site.  If you have more questions, let me know, and I'll happily answer them.  But that's a decent place to start on this question.

 Dear Janine thanks a lot for the opportunity to read your interesting thesis,  but I am unconvinced of many arguments put forward in your paper.  First at all that men are resistant to kill other human beings in the past history of mankind.  As you may easily realize, the focus of my question was on  the ancient humans and not on the modern wars.  The very fact that (western) men of  XX° century may be more resistant to kill other humans clearly depends on the huge abundance of ethical, religious and ideological arguments put against killing, which inform  the "feeling" of  most modern western societies.  But what about non-western societies? And even more so, what about the past hunter-gatherers societies? For example, were Vietcongs reluctant to kill American soldiers, who invaded their country ? Were Vietcongs affected by the same psychiatric disorders affecting the Americans soldiers after war? Unfortunately, but logically, we have no data on this, but I don't think so anyway.  Admiteddly, much depends on the value attributed to the life in each culture or society, and we know that cultures differ a lot about this. Life value in modern western societies is unbelievably different from that attributed in undeveloped countries or in remnant hunter-gatherers groups. I think that considering only the perspectives of people living in modern western countries should be totally misleading about it.. 

I do talk about archeological evidence that men in hunter-gatherer societies deliberately made their weapons less likely to kill before fighting with other tribes.  Specifically tribes in New Zealand would take the fletching off their arrows before fighting other humans (the feathers on the arrows make them much more accurate, and they were used when hunting for food).

There's more solid archeological evidence dating back to the US Civil War (1860), Waterloo, and the British wars against the Zulu, as well as in depth research on French soldiers in 1860, but those may be too Western or too recent for your purposes.

You could look at animal studies that compare the differences between social, pack carnivores with herbivores, showing that (for example) wolves fight each other for dominance in such a way that they are less likely to injure each other, but turtle doves don't - when turtle doves fight, it's generally to the death.

Ancient Mesopotamia and the European Stone Age pitted farmers against pastoralists (animal herders, etc.).  The latter easily adapted to using chariots, a warrior class, and to battle and to killing, likely because of their familiarity with controlling flocks of animals and with the necessity of killing animals - they had to learn to kill, and they had an easier time moving on to killing humans than farmers did.  This could account for the success of the Huns and the Mongols.  These invaders however primarily relied on "shock and awe" blustering before deciding hand-to-hand combat and killing was necessary.  

People talk about "fight or flight" - in social animals (including humans) there is universal evidence that, especially within in-groups, the choice is actually "posture or submit" before "fight or flight."  Wolves growl and bark in contests for rank before engaging in actual fighting, and the contest is often won when one wolf realizes he is outmatched.  The loser then bares his throat and the winner lightly touches his teeth to it without biting to show that he won but doesn't need to kill.  Both walk away.

You can see gang members and frat boys doing the same thing: "Are you talking to me?  You wanna fight?"  The first attacks, if no one backs down, are often weak but dramatic round-house punches, with the hope that friends intervene and give an excuse to back down while saving face.  This is similar to, as I mentioned, New Zealand tribes and the Masai in Kenya who don't try to kill their enemies when they fight other tribes, but who get status points simply for facing the battle and not running.

Again, though, I don't know how much of this is relevant to your research.  Hopefully it has been an interesting read, at least.  :)

Thank you again Janine for your interesting data and comments. I would only remarck that  while violence among in-groups members is obviously ritualized,  violence against out-group members rarely it is. That's the problem. And also,  tribes in New Zealand would take the fletching off their arrows before fighting other humans simply because fighting is so close in these contexts that  makes useless the shot's precision. Papuan men are confronting some few meters a part, face to face,  while the prey are running far way from the hunters and precision of shot become crucial.  Sorry, but I am an  incurable skeptic about the good nature of  the man.

You don't have to interpret the "posture / submit" response as a result of man's good nature.

For wolves, it is in the best interest of the pack that all wolves be healthy and uninjured.  If conflict and issues of rank and dominance can be settled through posturing rather than fighting, that's better for the group.  Fighting can mean injury, even for the victor, which weakens the pack.