A common bit of pop evolutionary psychology is that men want quantity in their sexual partners, because that is how they maximise their chances of reproducing, while women want quality, because that is how they maximise the chances of their off-spring surviving and reproducing in turn. In "sex by the numbers" I showed that the average number of partners must be about the same for men and women, and explained why women might want quantity just as much as men. Now I am going to explain why men might want quality just as much as women.
Imagine the following two worlds. In the first, every man gets to have sex with every woman. In the second, every man gets to have sex with just one woman. If we ignore various complications like venereal disease, infertility, strength, attractiveness, and so on, then the probability of reproductive success for each man turns out to be the same in both worlds. A one in a million chance of reproducing with each of a million women is actually not as good as a sure thing with just one woman.
OK, so some of those complications we ignored look like pretty big complications, but there is still an important point to note here. Boinking lots of women will not do much for a man's reproductive success rate if lots of other men are boinking the same women. A man might do just as well to focus his efforts on boinking just a few woman, or even one woman, and making sure that no other men are boinking those particular women.
Exactly where things settle out will depend on all those complications we ignored. In a population where infertility is common, promiscuity will pay more, in a population where venereal diseases are common, promiscuity will cost more, and so on.
If we look at our close relatives we find species that have gravitated towards the extremes. Bonobos are almost completely promiscuous. Male gorillas jealously guard access to a small harem. If we look at humans though, we find great variation within the species itself. Some humans are perfectly monogamous, some are highly promiscuous, most range somewhere in between.
So what should we conclude? At the most abstract level evolutionary theory gives us no reason to think that promiscuity is more natural for men than monogamy. There are good evolutionary reasons to think that men would, under certain circumstances, prefer quality (or at least exclusivity) over quantity.
I've noticed a couple of times that when people argue for Monogamy, they tend to (intentionally or not) make strawman case against polygamy involving some impossibly large number of partners. Save for a handful of extreme cases in ancient society and teenage fantasy, no one in real life is talking about having more than say 10 partners over a lifetime. Yet the Monogamists insist it's either one partner or a hundred, and since no one can possibly have a meaningful relationship with a hundred, monogamy is the only way to have meaningful relationships.
I think it's a sign of fundamental weakness of the position to have to resort to these sort of parlour tricks.
Comment by Ethlite — June 22, 2005 @ 6:59 pm
This argument doesn't really depend on the numbers. Even if a man has just two, or three, or four, more partners, it won't help his prospects if those women are sleeping with two, or three, or four other men. Exclusive access to one will be just as good. Of course it is true that exclusive access to many would be better.
Serial monogamy wasn't addressed at all. The trade-off between serial monogamy and one-woman-in-a-lifetime monogamy is a whole different story.
Comment by Dr. Strangelove — June 22, 2005 @ 7:22 pm
Sorry Strangelove, but I find your arguments here wholely unconvincing. Firstly, it's based on a common but incorrect assumption that a man is consciously trying to impregnate every woman he sleeps with. That's just absurd. In fact, in most cases of those trying to sleep around, they either don't care, or actively try to avoid any such thing. The reproductive drive isn't a matter of conscious choice, except in certain circumstances, and those are usually the ones you describe: where a man has monopoly control over one or more women. In other cases, he doesn't really care if other men are sleeping with the girl too. He just wants sex. What your body / genes "want" (even though they don't have conscious desire as such) and what you as a conscious individual wants, are not the same thing. They never have been. It's like saying that a lion hunts the weakest looking antelope, because he wants to improve the gene pool of the antelope herd. Rather, the lion just wants a meal, and he'll take the easiest option available. It's an unintended outcome on the part of the lion that matters as far as evolution is concerned. Take another example: rape by rampaging armies. There is no intention to spread / enhance genetic diversity, but it works pretty effectively all the same.
Second major problem with your reasoning: Even if a man does consciously set out to have babies, a woman can only be pregant once in a period of roughly 10 months. Thus, a man who sleeps with multiple partners in quick succession has a significantly better chance of spreading his genes than does a man who sleeps with only one woman. Certain kings and emperors have been known to have fathered more than a 100 children. This is clearly impossible if one attempts to monopolise just one woman. If you were physically able to sleep with 1 million women, then if only 0.1% of them would ended up pregnant, you'd be the most successful male of all time, for a reproductive point of view.
It wouldn't matter, from the gene's "point of view" if some of those women might be pregant from another man ... just as long as lots of them are yours. Who cares if you know which ones? Your genes have still accomplished their principle task, to reproduce themselves.
Comment by Filthy Stinking No.9 — June 23, 2005 @ 11:54 am
There was no such assumption in the argument I gave. The assumption (in most evolutionary psychological arguments) is that if S is the strategy that maximises successful reproduction for a particular organism, then organisms of that type will evolve towards a psychology which is well suited to executing S. Now that doesn't mean the organism will be aware of S, and be consciously trying to execute S. The claim is just that whatever motives (etc) the organism does have will tend to lead it to execute S.
Take the argument I was responding to. It starts with the claim that the best reproductive strategy for male humans is to have sex with as many women as possible. It concludes that male humans will have a psychology that is set up to do just this.
My argument is an objection to the claim that sleeping with as many women as possible is the best reproductive strategy. It aims to show that getting exclusive access to fewer women could be just as effective as non-exclusive access to more women.
This is the claim I was objecting to. The man who sleeps with many women will *not* have better prospects if the women he sleeps with are sleeping with lots of other men. If the man who sleeps with just one woman has exclusive access to that one woman then he may well have better prospects.
Right, but it should be obvious that monopolising many women is better than monopolising just one women. This is just more support to the claim that men might be more interested in exclusive access (quality) than in more access (quanity).
This is not quite right. If single mothers typically fail to raise their children successfully (not so common now, but I suspect very common in our species past) then it can become very important to know which children are yours. Again, the guy who knows which children are his, and invests resources accordingly, might do much better than the guy who has no idea which children are his. The later might have more children, but the former will have more success in getting his children to the point where they can reproduce in turn.
Comment by Dr. Strangelove — June 23, 2005 @ 1:37 pm
Strangelove ... it still doesn't work.
Your reponse to my first objection only works if you ignore the real world. Most men, if given the opportunity, will sleep with multiple partners. The ones who don't, usually restrain themselves for fear of the consequences, such as losing their existing and reliable source of sex, or having the mother of your existing children walk out on you, etc. Clearly the behaviour that has been bred into men by their evolution is to want sex with lots of different people. The behaviours to which you refer point in the opposite direction of the case you are putting. How many teenage boys have you come across who fantasise about sleeping with just one woman?
Second point. So what if the girl you slept with also sleeps with other men? As long as your sperm is the first to the jackpot, it's irrelevant. Doesn't matter if she slept with someone the day before and another one the day after. Assuming she is not already pregnant, your chances of impregnating her are not diminished by her sexual activity, unless of course she's caught a disease that makes her less fertile etc. You better spell out what you mean.
Your chances of knowing if the kid is yours are diminished, that's true. But your objection to my point there only works if you're assuming a society with family relationships much like we have in the modern world. In many tribal societies, the raising of the kids is a collective effort. Secondly, from this point of view, in societies where there is a family situation with a mother requiring a single male protector/provider (not necessarily the majority of human experience) the ideal is in fact to sleep with women who are also sleeping with other men (the exact opposite of your point). You want to find as many women as you can who have stable partners and sleep with them. Then other men will solve the the problem of ensuring their survival, as long as they don't know of your sex with their partner, or at least they think it's more probable that the kid is theirs.
Given that it is quite possible for a man to have multiple women pregnant to him at the same time, and that incidents of death of both child and mother in childbirth were relatively high in pre-modern times, it seems a poor investment to rely on one woman alone to carry your genes. Jared Diamond, more famous for his "Guns Germs and Steel", wrote a book before that called "Why Sex is Fun" ... and one of his points is that in some primite tribe in the amazon he studied, cheating on partners wasn't that uncommon, and it usually happened when a man returned from the hunt with a rich catch.
If it's true (god knows how they would prove it) that there are millions of descendants of Genghis Khan floating around the world today, it seems to be proof positive that the strategy of spreading your genes with wild abandon is the way to go.
There are certainly advantages to monogamy. There may even be reasons why it's advantageous from an evolutionary point of view, but I don't think you've made your case. I'm probably more inclined towards it that most men I know, but if my aim in life was to have as many kids as possible who would grow old enough to have as many kids of their own in turn ... I sure wouldn't be confining myself the just one woman, nor even a small number, if I had ways or means (voluntary or otherwise) to impregnate lots of women. This is speaking from the point of view of a person in the pre-modern world. In the modern world, it's a bit more complicated, because of contraception, and abortion etc ... these days, it requires more persuasion to get a woman to carry your child to term, and it may be that under these circumstances, it does in fact become an evolutionary advantage to limit yourself to one (or possible 2 or 3 if you're got the resources / skill to carry it off). However, this reasoning doesn't apply in the pre-modern world.
Comment by Filthy Stinking No.9 — June 23, 2005 @ 2:35 pm
But almost none will take up every sexual opportunity that comes along, and a few will voluntarily refrain from sex for their entire lives.
Surveys on sexual behaviour show that most men cheat on their wives, but they also show that a substantial majority never cheat on their wives (or at least won't admit it even for an anonymous survey), and the vast majority don't do it very often. So the real world data is actually a very poor fit for the "men want quantity" theory, and a much better fit for my claim that both men and women fall somewhere in the middle - wanting some mixture of quality and quantity.
Evolutionary arguments, of the kind we have been looking at, are only going to tell you which strategies human psychology might be set up to execute. Such arguments are unlikely to tell you much about the specific motives that get humans to execute these strategies. In this case it might be some combination of fear, jealousy, honesty, lethargy, obsession, whatever. The question I have been addressing is not so much how men are motivated to limit their sexual attention to a smaller number of women, but whether this would make evolutionary sense.
I don't spend a lot of time discussing sexual fantasies with teenage boys, but I suspect very few feel the need to fantasize about a different woman every night.
If your sperm is the first to the jackpot - but the problem is that, as her number of partners goes up, your prospects go down. If she slept with someone else the day before then there is a very good chance that she is already pregnant. Also sperm can survive for up to a few days after sex, and fertilization often takes place a day or two later, so your sperm might well wind up competing with the sperm of someone she sleeps with a day or two later.
In primate species that are highly promiscuous, like chimps, the male genitals are relatively large, and the quantity of sperm ejaculated is relatively high precisely because of this sort of competition. In species that are less promiscuous, like gorillas, the genitals are smaller and quantity of ejaculate less. Humans fall somewhere in the middle.
And notably this is most common where there is a limited gene pool (i.e they are all inbred). In societies like that it really doesn't matter which kids are yours because they all have the same genes. But it also doesn't matter much whether you have sex at all. "Your" genes will get passed along whether it is you, or your brother, or your cousin, who does the deed.
The "as long as they don't know" part is the problem. If other men are pursuing a strategy of exclusive access, say by flying into a jealous rage and killing anyone they find sleeping with their women, then this is going to be a highly risky strategy. It also presupposes that most other men are not following the same strategy.
Which still leaves the possibility (as with rape) that some men are wired to work this way, or maybe all men are wired to work this way under certain circumstances.
Not at all. It is a pretty safe bet that we are all descended from a single male who lived in the relatively recent past (within the last few thousand years). But the fact that this guy had lots of descendants tells us very little about how many off-spring he had. A man who has 2 kids, both of which survive and have two kids, etc, will do better than a man who has ten kids, only one of which survives to have ten kids, etc.
Comment by Dr. Strangelove — June 23, 2005 @ 4:50 pm
Strangelove, I'm going to leave you to rebut your own points. Have a go. There are so many holes in this argument that I find it impossible to believe that you can't find them for yourself. In fact, I know you can. You pride yourself on being able to argue any point convincingly. Some of the points you just made ... well, if it was anyone else, my reponse would be "come on, you can't be serious" because most people argue for things they believe in. As Ethlite said, I get the impression you don't actually believe in this argument, but you just think you can (or should?) make it. It's considerably below your normal standards.
Comment by Filthy Stinking No.9 — June 24, 2005 @ 8:42 am
That's an exceptionally cruel thing to do. Anway, here goes.
I don't think there is anything much wrong with the argument as it is except for the following two points:
(1) It isn't really an argument for monogamy.
(2) It's barely an argument for anything.
Starting with (2). The argument is just an objection to the pop evolutionary psychology argument cited at the top. It is often assumed that, for males, access to more sexual partners is the best strategy. All I have done is point out that more exclusive access to sexual partners might be as good or even better.
But, now getting to (1), this isn't exactly an argument for monogamy, or even an argument for the claim that monogamy comes naturally. At most it is just the first step of such an argument and, as it stands, it could just as easily be the first step of an argument for exclusive polygamy.
Comment by Dr. Strangelove — June 24, 2005 @ 3:33 pm
Yes, and I suspect that is because even you, Dr. Strangelove, cannot construe a solid argument for Monogamy for Men - depsite what the title of the post says. On the hand, your previous posting about polygamy for women is actually quite a bit more solid. (not that I can speak from personal experience, of course).
So if we can agree that monogamy is not an optimal strategy for either sexes, the obvious next question is, why are we still pretending that it's the only way? Serial monogamy is the law in all modern societies, Is it just pure inertia? Or is there some other underlying reason we've missed?
Comment by Ethlite — June 24, 2005 @ 10:34 pm
Here is a quick sketch of how the rest of the argument for monogamy would go.
The arguments I gave above explain why it makes evolutionary sense for men to want exclusive access. At the end of "sex by the numbers" I gave a very brief explanation of why it makes evolutionary sense for women to want at least one "main man".
Do men and women actually want these things? Obviously. How much do they want these things, compared to the other things they want? Don't know. But if we suppose that men and women want these things quite a lot then it is not hard to get an argument for monogamy going.
If men want exclusive access, and women want support, then it should come as no surprise that they cut deals that look like marriage. Still we might wonder, why monogamy rather than some form of polygamy? After all, wouldn't men do better with multiple wives? Wouldn't women do better with multiple husbands?
It's not hard to see why women with multiple husbands is uncommon. The husbands would not get exclusive access, which we are supposing is their motive for entering into marriage. Still, this might work under the right economic and demographic circumstances (like maybe a shortage of women, and a high cost of maintenance for children).
It's harder to see why men with multiple wives is not the norm. It was, and is, more common than women with multiple husbands, but monogamy has always been more common, and in modern societies it is far more common. Why is this? I think it is because of the relative absence of oppression in modern societies.
Men who are entirely shut out of sexual access to women will usually resort to violence to get access if other means fail. So if you have a situation where some men have all the access, and other men have none, then this will only be stable if the guys with access are able to oppress the guys with no access. The relative equality of power in modern societies, among men, makes polygamy incompatible with social stablity.
Of course there is more to be said. We might still wonder why women would care about their husbands cheating on the side if all they care about is economic support. I'll get to that later.
Comment by Dr. Strangelove — June 25, 2005 @ 6:35 pm
I heard this on the radio recently and have been struggling to find a web reference.
Experiments involving the attachment of artificial combs of varying attractiveness to roosters show that they quickly move to a strategy most appropriate to their status. Attractive roosters become highly promiscuous and uninterested in long term partnerships, while unattractive roosters try to secure exclusivity with one female. This is said to have parallels to human behaviour.
Female strategies weren't discussed; perhaps they weren't as relevant given the difference in breeding between the species.
So it doesn't sound like either of you are wrong as both strategies will apply in evolutionarily stable proportions of the population.
Comment by sausageofdoom — July 17, 2005 @ 8:29 am
Well, yeah. I'd imagine, with the ability to perform abstract thoughts, women would not always be interested in the most attractive male, given that they are unlikely to be faithful. Also, unlike roosters, 'attractiveness' itself is a multi-dimensional subject for humans.
I had no idea that the concept of long term relationship can exist for simple animals like roosters though.
Comment by Ethlite — July 19, 2005 @ 6:24 pm