September 03, 2008
Natural Selection Caused Human Male Belligerency

Just punched someone? Blame it on natural selection. What to join the Marines and go into combat? Your genes are your puppeteer. Dream of shooting down enemies? Your genetic alleles for violence are expressing themselves in your brain. We want to beat up on other people because our genes tell us to. These results come from an unverified mathematical model. But surely natural selection has made men violent. Just the mechanism of exactly how needs to get filled in.

The mathematical analysis of the evolution war by Laurent Lehmann and Prof Marc Feldman of Stanford University focused on small-scale, pre-state societies, for instance hunter-gatherers societies.

In the Proceedings of the Royal Society, Biological Sciences, the study shows that the "selective pressure" on genes linked with belligerence and bravery can be substantial even in groups of large size, so that evolution has smiled on the most aggressive and audacious group.

What I want to know: Is belligerency getting selected for or against? Does the answer to the question differ between societies?

Some guys might die in wars with the next village while still promoting their genes through their surviving relatives.

Some men who carry genetic variants that promote bravery might perish because of them, but the ones who survive may win more battles through their greater daring. The resulting opportunities for rape and pillage can create a net evolutionary benefit.

By having sex with their vanquished enemies’ wives and children, and by taking land on which their own womenfolk could grow or gather more food, particularly courageous and successful warriors would have more offspring who share their genes. “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,” the scientists said.

Really large scale societies that have been settled and centrally controlled for a long time (e.g. China) might have experienced long periods of selection against belligerency as the belligerent men ran afoul of central rule and got imprisoned or killed. So we might expect to find some groups to have lower frequencies of the genetic variants which cause male aggression.

Here is the abstract of the paper (PDF) and the full paper is at that link.

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.

Confirmation for genetic theorizing of this sort will not be long in coming. The costs of genetic testing have fallen by orders of magnitude in the last 10 years and the costs keep dropping. So the quantity of genetic testing is soaring. This enables large scale comparison of people for genetic and behavioral differences.

Once the genetic sources of violence become well characterized do you think the genetically most violence-prone people should be allowed to pass along their violence-causing genetic alleles to offspring?

Share |      Randall Parker, 2008 September 03 09:53 PM  Brain Evolution

JBS said at September 3, 2008 10:36 PM:

"Once the genetic sources of violence become well characterized do you think the genetically most violence-prone people should be allowed to pass along their violence-causing genetic alleles to offspring?"

All nations need a warrior class for defense (and offense). It is likely governments will offer finacial incentives to some percentage of women to have embryos screened for desirable traits the government needs, such as genes making someone an excellent soldier, a great scientist, etc. This would be even more effective when artificial wombs come online. Then governments could order up a batch of genetically desirable babies, and, if the birth rate is low, increase the number of births enough to have a steady rate of population growth. Parents could be paid to adopt these babies.

I'm surprised the Chinese don't offer financial incentives to try and get women to screen for female embryos rather than male embryos in order to improve the Chinese gender balance ratio.

K said at September 4, 2008 1:22 AM:

This topic keeps coming around. As more is known about genetics I see two big implications. They have commented about before.

The first is obvious, if our genes control us we have less or no personal responsibility for our acts. This is merely an extension of our legal and moral traditions which say those who cannot control their impulses or understand the nature of their acts are not criminals. Neither are they exempt from consequences; the law and the state just deal with them differently. Usually they are confined to mental hospitals.

A societal crap shoot then follows. Doctors try to guess if and when it is safe to release the mental patient. The judge tries to guess if those Doctors actually know. And civil libertarians attempt, whenever they can, to release as many as possible.

The second implication is also obvious. If genes control then society arguably has a right to alter the individual and remove or neutralize undesired behaviors. And the weasel word is "undesired".

JBS pointed to the reverse side of behavior alteration. Aggressive and ruthless behavior may be desired. Any tyranny would prefers police that will support the state without limits - the equivalent of the Nazi "I was just following orders" defense. And that defense is perfectly valid for those altered or bred to follow those orders.

JBS also noted the racial undertones of state controlled reproduction. Why just create obedient babies? Why not create those with the physical characteristics of those in control? Race - imagined or not - will matter if it is deemed to matter. And there is a lot of deeming in all parts of the world.

Brock said at September 4, 2008 8:47 AM:

"Really large scale societies that have been settled and centrally controlled for a long time (e.g. China) might have experienced long periods of selection against belligerency as the belligerent men ran afoul of central rule and got imprisoned or killed."

Based on my experience, and I'm married to one, the Chinese are plenty belligerent. :)

But while I get the point, I disagree that belligerence would be selected against. It would still be a useful trait, if tempered by patience and cunning. Belligerence is no less useful in politics and business than it is in war, it's just channeled in a different way. Successful (aka, belligerent) businessmen and politicians would tend to be productively successful.

Randall Parker said at September 4, 2008 9:09 PM:

Brock, some forms of belligerence get people locked up and executed. That's selection against those genes.

As for a limited amount of belligerence getting selected for: Sure. But the optimal level of belligerence for reproducing was lower under a Chinese emperor than among the Yanomamo.

Xenophon Hendrix said at September 5, 2008 2:14 AM:

I suspect there will be a large number of trade-offs. Suppose, for example, that "violence" is mostly a measure of sensitivity to testosterone. Well, we already know that high testosterone is correlated with both good and bad things. Athletes, business leaders, and violent criminals all tend to be either high T or highly sensitive to T. Are we willing to get rid of the good in order to get rid of the bad?

Brock said at September 5, 2008 7:04 AM:

Randall, as a New York corporate attorney I work with Wall Street bankers every day. Believe me, they're belligerent. My point was that they are not less aggressive than a Yanomamo warrior, but that they channel their aggression differently. The ability to channel that's been selected FOR; aggression has NOT been selected against. To paraphrase the paper, they are certainly using force to to seize useful resources. Bald-faced aggression in business, politics and organized war still pays really big dividends. I'm talking $1~5 million dollar year end bonus kind of dividends.

Jake Peachey said at September 6, 2008 7:40 PM:

After philosophical adventures into Tabula Rasa (Man born with clean slate) science seems to be interested in man as an animal of feral instincts. Possibly for the utility of excusing contravention of what used to be traditional morality. And perhaps partly for the purpose of trying to find a basis of moral and ethical philosophy outside of the traditional Christian base.

But as the Bible states the heart of man is deceitful and above all desperately wicked. No Tabula Rosa here in man. This is referring to the natural instincts of the feral animal Man has overcome in order to build society and civilization. Think of the little baby arriving with this "read-only memory." Somebody made this comment: it is as much a function for young adults to raise children as it is for children to make young adults grow up. It doesn't take long, particularly with more than one or two children, to suddenly realize the need of constant reinforced teaching with supportive environment and community.

But unlike any other creatures of God's creation, man has "random access " capability in which operating software can be installed to counteract and neutralize the feral instincts of the animal. The Christian faith holds that man is a free moral agent---- but is held accountable, meaning he has a choice regardless of circumstance. (Alexander Solzhenitsyn writes of individuals who suffered enormously and were murdered for refusing to bear false witness in Stalinist show trials) ----

Philosopher Hobbes felt that such was the animal nature of man that it took tyrannical central authority to build sufficient controls for the foundation of civil society. And so it seemed for much of human history

But what happened in the foundation and building of this country is quite different. I don't think anything quite like this happened before in history. People coming together from various parts of the country including immigrants establishing governance based on rule of law in the territories. It is true the federal government had its forts and soldiers to deal with the Indians in the territories, but that was not the basis of organizing political power in the territories. The top-down model of the central government first establishing a protectorate, with a military governor in control, is not how it happened.

I find in Laura Ingalls Wilder's simple but well-written stories inspirational and providing insight into the mind of original Americans. Fourth of July celebrations were religious services, of a sort, by men with the law written in their hearts.

A farmer/settler selected as master of ceremonies: "Well boys, I'm not much good at public speaking, but today is the glorious fourth. This is the day and date when our forefathers cut loose from the despots of Europe................... (S)o here we are today, every man Jack of us a free and independent citizen of God's country, the only country on earth were man is free and independent." Etc.

Next, the reading of the Declaration of Independence with hats off. "Laura and Carrie knew the Declaration by heart, of course, but it gave them a solemn, glorious feeling to hear the words".

Next the song of My Country 'Tis Of Thee.

And now Laura when at approximately the age of 14: "suddenly she had a completely new thought. The declaration and the song came together in her mind and she thought: God is America's king. Her whole mind seemed to be lighted up by that thought. This is what it means to be free....... the laws of nature and of nature's God endow you with the right to life and liberty... you have to keep the laws of God, for God's law is the only thing that gives you the right to be free." Laura instinctively understood that to have maximum freedom, without the Hobbesian world of anarchy, depended upon man's voluntary internalization of the rule of law, which is what the Christian faith provided.

The operating software of the greatest civilization ever.This kind of software will never come from science. The only thing with science can offer is the lessons of nature: survival of the fittest, kill or be killed. Even the "rule of law" is a formulation that can only be called religious.

A unique and interesting feature of successful religious- philosophical beliefs that underpins the development of civilization is that it has never, will never be developed from" scientific approach" but from religious teachers with transcendant understanding and perception which the worldly-wise will de-construct and think themselves wise. However, they themselves of are hopelessly inadequate to develop a religious philosophical system that will work. Because it will not necessarily follow the current intellectual fad (which is always evolving), a successful system that is timeless will not always seem to follow rational logic, because things are infinitely more complex then the solutions proposed by some (Freud--Marx). Thus Christians believe in the transcendant inspiration of the Bible. It speaks to the being of man with three-dimensional perception and understanding to those who are open to its transcendant dimension

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