I am reading the book You, The Owners Manual and in the chapter about sex it states “Humans are biologically - if not always socially - monogamous creatures.”
It was not anything he was trying to prove, just a quick comment in the chapter. It surprised me because I always thought the opposite was true.
Any thoughts about why he would have said this?
Also, for those who have read it, do you think this a credible source of health information?
Everything I’ve read indicates that humans are serially monogamous. We tend to bond for 3 - 5 years in relatively monogamy and then break apart and find another parter.
In the wild, children who have two parents would be much more likely to survive and be socialized properly, which increases their chances at reproduction, and so on and so forth. So if there’s a biological component to monogamy, there’s definitely selection pressure for it.
There are a lot of evolution threads that point out in more detail why human males are slightly polygamous… tending to be monogamous.
Short evolutionary explanation:
The bigger the testicles the more sex you’ll be having with different females. The smaller the less competition and less need to impregnate females. Chimps have a lot of sex with different females and have big testes for size. Gorillas have exclusive acess and have small testes especially for their size. Human males have testes a bit over the average for their size… so we are closer to monogamous apes than to polygamous apes. So in these terms we are built to be a bit “unfaithful”. (Some books I’ve read also indicate women have some reproduction strategies that indicate its good to have genes from different men.)
So were are not monogamous strictly speaking.
To add to the biology thing, there is also the “killer sperm” component of ejaculate, which contains a certain number of sperm which will kill other men’s sperm rather than fertilise an egg; further, there tend to be larger ejaculations with a higher proportion of killer sperm when a couple is reunited after a trip (which would provide cheating opportunities).
I’ve read that a woman’s orgasm strength and frequency has some correlation with her fertility (the spasmodic motion brings the cervix into position to get direct contact with seminal emissions); it’s not uncommon for women to report stronger, more frequent, and more intense orgasms with illicit lovers. (Presumably, if there is a biological mechanism driving this difference, it is because normally an organism will cheat with something with better apparent genetics than one’s social partner.)
Biologically speaking, I would characterise humans as ‘socially monogamous with a slight tendency towards polygyny, with both sexes having a tendency to cheat if it’s appealing and they can get away with it’.
Good summary !
Now we are free to avoid being driven by our natural impulses… or embrace them… 
That hypothesis has come under serious sustained attack, if not been totally debunked.
The first problem is that it fails to address the fact that humans females have none of the signs of fertility found in gorillas or chimpanzees, and that humans have sex more frequently than either species as result, and far more frequently during infertile periods. That alone could account for the difference.
The next problem is that humans are the only bipedal ape. As a result human females tend to ‘leak’ far more than other apes, resulting in greater sperm loss. Once again, that could account for the difference by itself.
The next issue is that gorillas are not clearly more monogamous than humans. Female gorillas routinely cheat and will almost always try to mate with the next-to-senior bull if they have the opportunity to do so undetected. The observed infidelity rate for gorillas is far higher than anything even suggested for any human population. Much less observed. So gorillas should have much larger testicles than humans, yet they don’t.
The next issue is that humans and are carnivorous and live on high energy, low volume diets. Gorillas are almost exclusively vegetarian and live on low energy, high volume diets. Semen contains a lot of protein, it’s not a cheap resource to produce energy wise. Just based on dietary limitation of resource production we would predict that gorillas would produce less sperm than humans or chimps.
Linked to that is the issue of temperature control. High temperature interferes with sperm production requiring larger testes. Humans and chimps are very active creatures, whereas gorillas are fairly sedentary browsers, as a result gorilla testicles shave less heat build up to worry about. That could also account for a discrepancy between the two groups.
Then we come to the problem that humans have abnormally large penises. The size of the penis and testicles seems to be genetically linked to some degree. Human testicles may be large simply because we have large penises.
Next we have to deal with totally different social structures. Gorilla form strong harems ,with one male ‘exclusively’ servicing numerous females. Any male may only be dominant for a short period of his life, or he ,may never become dominant and never have a chance to mate, yet all males have to be ready to mate immediately if the opportunity presents itself. That produces a huge constraint on gorilla testicles because they can’t afford to permanently carry around energy expensive organs that only get used for a few months of their life, but they can’t afford to have small organs because if they do rise to dominance they may be need them for several years. The solution is to come up with a mid-range organ that works reasonably when required, but doesn’t chew vast amounts of energy when not in use. Chimps in contrast have the opportunity to mate continuously, and as a result can afford to gamble on large organs that constantly use energy because they are in constant use. Humans fall into a mid-range situation where human males may not have an opportunity to mate for many years, particularly while young, but due to air bonding may mate regularly once a mate has been found. We adopt a strategy somewhere between a gorilla and a chimpanzee in producing organs that are moderately expensive to maintain but work quite well. IOW we could just as easily explain the difference because human were intended to be exclusively monogamous with no pre-marital sex.
And finally bonobos and chimps are even more closely linked than humans and chimps. Bonobos are even more promiscuous than chimps, yet they have slightly smaller testicles.
Basically the whole hypothesis compares apples and oranges. By including gorillas which are so different from humans it’s throwing carrots in there as well. It’s a hypothesis that doesn’t have an ounce of evidential support beyond the initial observations that led to its construction. I have never even seen one of the proponents of the theory attempt to back it up by looking at the sperm counts of these animals, rather than It contains numerous assumptions, invalid comparisons and logical flaws.
Tyring to use this ‘hypothesis’ to support the idea that humans aren’t monogamous just doesn’t work.
What are ‘killer sperm’? How do they work? Reference please.
I know that human males tend to produce more semen after re-unification, but they also produce more after stimulation and abstinence and it’s all but impossible to separate the three factors.
I submit for your approval the following non-scientific webpage dealing with Evolutionary Psychology vis-a-vis human mating behavior:
http://www.king.igs.net/~rogersk/mono.htm
(Warning: contains some images that are not work-safe)
Speaking in terms of evolution I don’t have much to say, but I can say without a doubt that we are definately not monogamous in thought. I was not programmed to be sexually attracted to one woman for the rest of my life. I doubt that there has been any sexually healthy male who had sexual thoughts about only one person in their liftime.
Before civilization when sex was amoral, like eating or sleeping, it seems reasonable to assume that his how we would have behaved sexually.
I’ve also been curious about this. I can’t find anything about it that I consider a credible source on google. Any suggestions on further reading?
Permit me to introduce to you the distinction between correlation and causation. One might equally conclude, on the basis of visting nightclubs, that alcohol acts to increase fertility.
Sociobiological appeals to the rationale for human monogomy (or polygamy) frequntly tend to be rooted in the observer’s bias and often on the assumption that the sexual act is primarily of reproductive function. The actual amount of promiscuity and the degree to which it is open versus clandestine is strongly controlled by social pressures rather than in a species-common genotype. The wide variation in sexuality among societies and individual humans within a society–from egregious bisexual promiscuity to prudish and frigid celebacy–argues against the impulse to monogomy or polgamy as a simple inherited trait.
Stranger
Digging up stuff on sperm types produces this article, which seems to indicate it’s a theory rather than the fact I thought it was (relevant comments near the bottom):
http://news.bbc.co.uk/1/hi/health/681172.stm
There do exist sperm that are incapable of fertilisation in any ejaculate; the big question seems to be whether these are basically wasted investment that doesn’t carry an evolutionary penalty, or whether some benefit is derived from them. Different types are observed, but whether that means anything is uncertain. So I overspoke on that one, and I consider myself corrected after further research. (The theory also seems to have at least a few extremely overenthusiastic proponents who think that it explains everything in the universe.)
I have also completely overloaded my comprehension capabilities by trying to skim scientific abstracts when I don’t really speak abstractspeak.
(Further googling provided a mathematical analysis of whether ‘soldier sperm’ are likely to evolve at all, the existence of which amuses me. http://evol.allenpress.com/evolonline/?request=get-abstract&issn=0014-3820&volume=54&issue=1&page=72 is the source.)
I believe that males tend to produce more sperm if the partner is involved in a situation more likely to involve adultery than one in which they aren’t. ie: if they go on a business trip across the country vs going hiking alone. This would indirectly seperate out the abstinence factor.
I’d have to see some strong evidence before I’d believe that.
How could you even test such an idea? If it just works because the woman claims she was hiking alone then how could it evolve in the first place? After all it’s not like most people would tell their partner the truth about cheating. As such it’s useless and could never evolve. But if it works even when a woman claims he was alone but was really with other men, or when she says she was with other men but was really alone then clearly it’s got nothing to do with separation but rather with some sort of subconscious cues.
And this is supposed to be a subconscious genetic trait yet for 99.999% of our history going for a hike and going on business trip were the same thing: wandering off to find food. It’s almost impossible to believe that such a trait could evolve in just the last 10, 00 years or so when the two became different.
Consider me highly sceptical.
I read or heard there’s a correlation between the size difference between the male and female (whole body), and how monogomous the male is. When the male is much bigger than the female, the male is much less monogomous (sea lion was given as an example). When they are about the same, the male is monogomous. The human male is slightly larger than the human female, and considered “slightly” less monogomous.
Thanks for the new insights… some remarks:
I hadn’t heard about the Gorilla females being given much of a chance of cheating… I thought male gorillas being so territorial were basically few and far between.
Big penis = big balls ? 
Aestethic issue ? Seems like a wierd connection.
I certainly won’t give the testes size as much credit… or any for sure… but still nothing seems to indicate monogamy programed onto us. Pair bonding yes… but not monogamy.
Someone posted the other idea… that male to female size indicating monogamy vs polygamy. Do you have anything to debunk that one too ? Seems a bit better than testes size.
Of course, you may be looking at it the wrong way. Given how many people are murdered each year for cheating on their spouses, we may have developed a wholly different kind of monogamy-straightjacket…
As sociology is inevitably a function of the human mind, and hence biology, the “sociological vs. biological” argument may be something of a false dichotomy. I’m sure that’s not an uncontroversial statement, but I thought I would just throw that in there.
There are some reasonable evolutionary arguments to be made for jealousy, which hypothetically would be manifest in our species due to selective pressures that naturally would affect a culture of humans, we being highly social animals. To the extent that society reflects the emotional needs of those who make it up, it seems reasonable to suspect couplings have conferred a selective advantage, though we’re clearly not incapable of other sorts of arrangements.
As individuals in a species typically represent a spectrum of characteristics about a norm for the species as a whole, I see no reason to argue from nature that monogamy is the most “natural” state for people. The most representative, sure, at least ostensibly. We’re also pretty good liars. There’s obviously a tension between the state of feeling monogamous and actually being monogamous. Maybe our natural state is to seek a coupling, and then test the boundaries of that coupling, with differing results for each couple.
Although it varies between species and even locations gorilla males aren’t terribly territorial It’s pretty common to find a gorilla tribe with 2 or three males present and the larger the average tribe size the more common multiple male tribes become. Female gorillas also seem to favour living in groups with multiple males if food isn’t restrictive. So it’s plausible that before human predation became common all gorillas lived in tribes with several males. There is almost always one dominant male who hypothetically mates exclusively with all females, and he beats the shit out of any other male who attempts to have sex. However if a female gorilla can manage to be alone with the next-to-senior silverback she almost always copulates. The theory is that this gives her protection from two sources, and also guarantees that if the dominant male is displaced the replacement will feel some duty of care for previous young because it just [I[might* be his.
Nobody is quite sure why human males have such oversized penises. It’s been suggested that it’s because human females have larger birth canals, but that ha some flaws. The fact that human penises are also heavily pigmented and prominently displayed has led to speculation that a big penis was useful either to attract mates or to intimidate rivals. The reason may not be strictly aesthetic, but whatever the reason the testicles and penis are both apparently influenced by the same genes and even the same hormones. So it may be that we have large balls simply because we benefited from having a large penis and the oversized nuts weren’t enough of a liability to counter that. It certainly makes any connections between testicle size and highly questionable.
No, I agree that the evidence for monogamy is a thin as the evidence for polygamy. I wasn’t suggesting otherwise, I was just pointing out that the arguments presented for polygamy have been pretty specious and at best tentative hypotheses, not scientific evidence.
The problem with this idea is that humans are a strongly sexually dimorphic species. We don’t just differ in body size we also differ in body shape, secondary sexual characteristics, behaviour/psychology, food sources, interaction with young and so on. IOW a human male isn’t just a scaled up version of the human female, he’s a different creature. That makes it very difficult to draw any inferences regarding the meaning of size dimorphism.
To give you some idea what I mean I will show you four birds. The first is the mute swan, in this species the male and female the same size. The next is the Huia where the male is 10% larger than the female. The next is the hornbill where the male is 15% larger than the female. The final is the red jungle fowl, in this species the male is 20% bigger than the female. Which of these species are monogamous and which are polygamous? Based on the information provided we might guess that the mute swan is almost entirely monogamous while the rest of the species become increasingly less monogamous as we progress down the list. So male hornbills should frequently fight with other males for mating rights, female huias should at least occasionally cheat and jungle fowl should be a harem society.
Of course this is mostly bollocks. In reality the mute swan is approximately monogamous, but they are fairly prone to cheating. Male hornbills aren’t at all aggressive and the species is even more monogamous than the swan. Huias are the most monogamous of all the species and the males and females live together constantly so the opportunity virtually never arises for cheating. The only species we got right was the jungle fowl, which does indeed have a single male harem society. So what went wrong? Simple, we didn’t factor in ecological and reproductive dimorphism in our equation.
Male and female swans are physically identical because they live identical lives even to the extent of incubating the eggs and caring for the young. Whatever evolutionary pressures dictate ideal male size also dictate female size.
Yes male hornbills are significantly larger, but not because they fight off rival males. They are larger because they have a reproductive strategy quite different to most birds. The male seals the nesting female up in a hollow branch using mud until the young have fledged. During that whole time the male is exclusively responsible for feeding himself, his mate and the young. He needs to be bigger because he has more demands placed on him to find food.
Huias are even more extremely dimorphic. They have completely different bills. The male bill is short and robust and good for breaking up wood. The female bill is long and thin and good for probing. Huias survived because the male broke up rotten logs and branches and the female then winkled the grubs out of them. The male needed to be larger not to fight off other males but because he had to perform strength related tasks to get food. The female performed primarily dexterity related tasks that required less physical size and strength. The males and females paired up for life and were never seen individually.
So what does all that tell us about humans? Well humans are a species where the evolution of bipedal gait has forced the production of a helpless infant that requires a lot of care and a debilitating birth process for the female. That leaves a time period where the male is almost the exclusive provider for the pair. That is directly analogous to the situation with hornbills, and just as monogamous male hornbills are forced to become larger to take care of a ‘helpless’ mate the same may well be true of humans. Similarly humans hunt high risk prey animals, and frequently suffer serious injury as a result. Moroever bipedal gait and foetal development means that for several months females can’t engage in such hunts effectively or without risking their own lives and the lives of their offspring. Just as huias developed size dimorphism because males and females had evolved to seek different food types this could be the case for humans.
Note that none of this is evidence for monogamy in humans. After all maybe males did get bigger to fight off rivals. But it is just as plausible that males got bigger to provide for helpless mates and young and because the females couldn’t effectively hunt large game. IOW size dimorphism could be equally used as an argument for exclusive monogamy or against it.
So after all that rambling the short answer is that many animals have developed size dimorphism specifically because they were monogamous rather than because they weren’t. Indeed the most extreme examples of size dimorphism occur in strictly monogamous species.
The females of the human species are very promiscuous. Males like to be but only a few can be so. Therefore there have been male attempts to restrict this female promiscuousity. These days the attempt has totally failed.
The idea that humans are monogamous is laughable. Ha ha!