August 30, 2008

Evolution of bravery and belligerence

Both bravery and belligerence increase an individual's chance of getting killed. This article proposes that this combination of traits may co-evolve: groups with belligerent cowards may start wars but not win them; groups with peaceful brave men will not start wars and, therefore, will not expand territorially; groups with belligerent and brave men will both start wars and win them, increasing the resources; thereby, its surviving men and women of their group will multiply.

This reminds me of a recent paper on parochial altruism. In that paper the authors argued for the co-evolution of parochialism (favoritism for one's group at the expense of others) and altruism (willingness to risk one's life for it). These traits are quite similar to belligerence and bravery. In the earlier paper, it was also suggested that parochialism increases the chance of intergroup conflict, and the two traits increase the probability of winning in such conflicts.

Personally, I am a bit skeptical of these theories of war, at least in the case of Greece. There may be something to them, but I don't think they explain the facts adequately.

An important fact is that the modern practice of men without offspring participating in wars does not reflect the facts of antiquity. While such men did participate in wars, so did their fathers. If we take the famed Paean of Salamis...
Forward, sons of the Greeks,
Liberate the fatherland, liberate
Your children, your women, the altars of the gods of your fathers
And the graves of your forebears:
Now is the fight for everything.
...we see a fairly explicit expression of war as sacrifice for one's women and children. So, while a case can be made for war as a calculated risk which may enhance one's future breeding opportunities, a case can also be made for it as regular kin selection, where men sacrifice themselves for their existing kin.

A second important point is the prevalence of the defensive war in the Greek tradition, which later became a part of the Western tradition. If war-like behavior and bravery had evolved in an offensive setting, then why was the need always felt to justify it in defensive terms, rather than as an opportunistic grab at the enemy's resources?

A culture of shame more than belligerence or opportunism accounts for willingness to go to war. Wars may start as random fluctuations in inter-group relations, or as real conflicts for resources. But, people participate in them not so much because they envision opportunities for themselves, but because of the shame that the alternative would bring. Known cowards who do not join the ranks or abandon the field would suffer consequences much more terrifying as an incentive than the positive incentive of conquering an enemy's land.

Finally, a special note must be made on "imperialistic" belligerence. We can assume that voluntary or coercive aggregation of tribes over the past led to an uneven distribution of the sizes of political entities. Whenever a large state found itself next to a small one, the temptation to conquer it would have been great, as such conquest would entail little risk.

Large states could both gather the required human resources for war (because men with the right psychological profile or need could be found in its larger territory), and to wage such wars successfully.

Proceedings of the Royal Society B doi: 10.1098/rspb.2008.0842

War and the evolution of belligerence and bravery

Laurent Lehmann, Marcus W. Feldman


Tribal war occurs when a coalition of individuals use force to seize reproduction-enhancing resources, and it may have affected human evolution. Here, we develop a population-genetic model for the coevolution of costly male belligerence and bravery when war occurs between groups of individuals in a spatially subdivided population. Belligerence is assumed to increase an actor's group probability of trying to conquer another group. An actor's bravery is assumed to increase his group's ability to conquer an attacked group. We show that the selective pressure on these two traits can be substantial even in groups of large size, and that they may be driven by two independent reproduction-enhancing resources: additional mates for males and additional territory (or material resources) for females. This has consequences for our understanding of the evolution of intertribal interactions, as hunter-gatherer societies are well known to have frequently raided neighbouring groups from whom they appropriated territory, goods and women.



McG said...

Its interesting to compare this to the fate of the "neutral nation" that inhabited the shores of many of the Great Lakes. They were first visited by the French Catholic Priests in the early 1600's and by 1650 they no longer existed as a nation. They were considered peace-loving, I don't know about their bravery but they were apparently not belligerent and in fact were tall for their race, some estimate six feet . In this instance it was the coming of the European and his desire for furs that caused the troubles. The Indians (Iroquois and Hurons) wanted guns, ammo and hatchets made of steel. For these they willingly traded their furs, especially Beaver. The neutral nation was probably as much assimilated as exterminated but the Force behind all this was economic. I have an interest in all this because my gggg..f Patrick Gregor McGregory was the first non-french white man west of the Adirondacks and was captured by Denonvilles Expedition in 1687. All this happened because of Britains desire to participate in the Fur trade which was monopolized by the French at that time. So the moral of the story is that it also pays to have a good defense available, in addition to being either brave or belligerent. Note, it may also be that the weapons the Hurons/Iroquois traded for gave them a technological advantage over the neutral nation??

terryt said...

A case can be made in favour of the theory. Even though an individual's chances of being killed become greater it's extremely unlikely his genes would not be shared by many others of his tribe. So the survivors' genes would flourish in the form of the remainder of the tribe.

Dienekes comments, "While such men did participate in wars, so did their fathers". It's usual in tribal wars for very few to be killed unless the battle become a total defeat, at which stage genocide usually occurs. At least that was the way things happened in New Zealand before firearms were introduced. So it's quite normal in such battles for fathers to be acompanied by their sons.

Helga Vierich-Drever said...

I found this interesting as a possible model for altered sexual selection occurring with the transition of economies from hunter-gatherer to horticultural or pastoral (leaving aside for the moment sedentary and warlike groups based on coastal marine resources.)

Then I came to the statement about "hunter-gatherer societies are well known to have frequently raided neighbouring groups from whom they appropriated territory, goods and women."

This nearly gave me heart failure. What on earth did the author use as a source for this extraordinary declaration?

I can only conclude that yet again someone is not understanding the profound difference between hunter-gatherer societies (reciprocal access to resources, egalitarian, highly mobile, generally without corporate groups) and horticultural or pastoral people (territorial, often sedentary or semi-sedentary, with lineage corporate groups, age grades, frequent raiding of neighboring groups).

This is a serious flaw in this particular paper and very misleading for the reader.

Grey said...

"Personally, I am a bit skeptical of these theories of war, at least in the case of Greece. There may be something to them, but I don't think they explain the facts adequately."

I think what they miss out is *when* the selection takes place.

War happens and losing can be catastrophic so cultures develop which apply selection pressures in peacetime for traits that are neccessary in wartime.

- team sports (the team captain gets the cheerleader)
- shame culture vis a vis bravery (coward = low status = shunning)

The selection pressure is applied artificially in peacetime to prepare young men for wartime.

Humans homoforming themselves.