Penis size, part 2 – Why are men obsessed with penis size?

First off, you may want to know: does size matter? The brief answer is this:

To men? – Definately!

To women? – It depends…

obsessionBut why? Why do men want to be bigger? That is, not only men who think they have a short penis, but also nearly half of those who think they are endowed with an average length penis, and about one fifth of those who are convinced they have an already larger than average penis? Studies find that the majority of men that undergo plastic surgery to enlarge their penis, actually start out with an average sized penis prior to surgery, and do not usually present a micropenis. So, what drives these men? Why do all men in communal showers (most often unobtrusively) check out how well-endowed the others are? Why are all virgin boys somewhat or sometimes very much concerned whether their size will be adequate? And why do some surveys find that women do not care about penis size, while others do? Is there any biological or psychological mechanism that is responsible for this “obsession” with penis size?

Bear with me cause the answers to these questions are rooted in the dawn of humanity and millenia of relatively little change in our lifestyle, and it is only in the end, after bearing with me to understand how evolution affected who we are as men and women, that you will be able to understand the obsession with penis size.

First off, some basic evolutionary principles. If you don’t have offspring, your traits are not passed on to the next generation. If your genes don’t get passed on for successive generations, your genes, and associated traits become rarer, or extinct (Whether they become extinct depends on whether your family members have the same bad luck in not being able to create generations of offspring.)

So the key to success? (And ultimately the key to understanding what drives everything?) Sex! – AND relations!

If the answer where to be just sex, and relationships wouldn’t matter, human beings wouldn’t be forming couples, but would instead mate with as many partners as possible to ensure enough genetic variation in their own offspring. This in turn would increase the likelihood of at least some offspring surviving, in case a change in environment (mostly new strains of diseases) would disadvantage the offspring of one partner but not of another.

This principle of increasing the odds to one’s own advantage is indeed driving human and all animal promiscuity: having sex with more than one partner increases the likelihood of your offspring surviving, thus ensuring your genes and traits being passed on, rather than going extinct. On the other hand, in comparison to any other animal, it takes a very long time for humans to grow from newly born to adult, and during all this time of growing up, human beings need quite some care and need to be safeguarded from dangers that might kill them before they grow up. This means that in order for your offspring to survive, it needs care, protection and it needs to learn. It is this long need for care, protection and learning for a newborn to fully grow up which has created a selection pressure on the forming of couples in humans, seemingly(!) foregoing the advantage of having offspring with multiple partners.

Despite the in the 60's relatively recent introduction of largely efficient contraceptives and the birth of the hippie movement propagating free love, sexual experimentation and promiscuity, the very same propagators of these movements tended to end up in couples having a preference for one particular partner.

Despite the in the 60’s relatively recent introduction of largely efficient contraceptives and the birth of the hippie movement propagating free love, sexual experimentation and promiscuity, the very same propagators of these movements tended to end up in couples having a preference for one particular partner.

Couple forming is not per sé an indication that in our evolutionary past, the male was needed for raising a child, nor does it indicate that humans are entirely monogamous. Although father figures often have a significant role for the growing child, for millenniums it was women (mothers and grandmothers) who spent the lion’s share of the work in raising offspring. So then why do people form couples? Why do women need men, and men need women? Some people claim it is because in our tribal past men took care of most of the food, bringing big game to the table every day. But if we actually observe life of humans still living in tribes, tribal men don’t catch big game all that often, and if they only catch something small (e.g. a bird), they eat it while out on the hunt without bringing anything back. In these current tribal societies as well as in those of our ancestors for countless generations, it were (and still are) women who collect most of the food, except for the occasional meat. So what function do men fulfill, other than an occasional contribution of meat and occasional impassing of knowledge to the offspring? The answer is: protection.

If a woman has a partner, the other men in the tribe will be much less likely to engage in non-consensual sex with her. I.e., having a partner acts as a preventive measure against (group)rape. If a woman has sex seemingly without regard for whether the man she has sex with cares for her or not, it will make other men objectify her. At times these men feel a sexual urge, some of them who didn’t get to have sex with her, may falsely feel entitled to have sex with her as well, ultimately leading to increased chances of coercion into sex. Also, if multiple men can have sex with a particular woman without having to endure any burden or responsibility, then why would a man willing to endure burdens do so for this particular woman, if he can save himself the effort and merely limit himself to sex with her? Not only that, but offspring of her would not be valued as much as that of a woman whose reputation is unblemished, and the child will have some disadvantages growing up. Hence words like ‘slut’ and ‘whore’ all carry a negative connotation, and women are sensitive to these words, because it can potentially preclude them from having a long-term partner AND the stigma of ‘bastard’ puts their offspring at a disadvantage in the level of care normally received  by adults and the level of respect normally received by peers. For the same reason, women apply these labels to potential rivals, to decrease the odds of a rival, thus hoping to increase the odds in her own favor. In essence, by forming a couple with a man, the woman enjoys protection of her reputation, of her privates, and of her offspring. A man in return gets to have offspring that is taken care for, and just as importantly will himself be taken care for. In tribes, men with a partner traditionally got taken care of by getting a more than fair share of the food collected by his partner throughout each day. As this tribal lifestyle of our ancestor still drives our behavior today, to this day we find that many women in long-term relationships find themselves complaining that “her man is a burden” or that all “men are like children”, and this is simply because men require being taken care of in order to tempt them to stay.

Promiscuity as well as providing safety for offspring to grow up by bonding with one partner ensure the successful spread of one's genes and associated traits. This holds true for both genders.

A fine line between bonding with one partner on the one hand (to provide care and safety for offspring), and promiscuity on the other ensure the successful spread of one’s genes and associated traits. This holds true for both genders.

Although couple forming brings an advantage to men, women and their offspring, on the other side both men and women can only give an extra advantage to their own genetic line if they have offspring with more than one person. As a result, every human being carries in him or her the two contradictory (not necessarily intentional) urges for (1) longer-term pair bonding, and (2) sex with multiple partners. It almost seems people are ‘programmed’ to have multiple partners. One way in which this occurs is by first making “mistakes” in relationships by engaging in relationships on good faith (e.g., because of an infatuation) but often without sufficiently knowing or testing the other. Or by ‘deciding’ to forego serious involvement after a heartbreak. Or by engaging in a relationship prior to being mature enough to fully understand what it takes to maintain a long-term relationship. These are all examples of combining both the urge to form a couple, as well as the urge to have sex with multiple partners. This is termed “serial monogamy”. Eventhough there are some people that solely engage in a single long-term relationship without first making a ‘mistake’, without cheating and without ever having had casual flings, even these long-term relationships with a first partner are not guaranteed to be for life. Approximately seven years (with a margin of error of a few years) seems to be the average breaking point of many long-term relationships, although of course there are relations that endure to death. Because of the urge to have multiple partners, relationships enduring to death usually have cycles where rough patches occur and when either partner is more vulnerable to seduction (although this does not necessarily occur). Apart from the socially acceptable serial monogamy way of having multiple partners (e.g., the having a history of unintentional mistakes), less socially acceptable acts such as having sexual affairs are so prevalent among humans that these behaviors also seem to be selected for.

Regardless of the way in which any particular human ends up having sex with multiple partners, it is this inherent urge to mate with multiple partners which drives the obsession with penis size. Specifically, it is women’s “promiscuity” in our evolution, not men’s which drives this obsession! (Yes, this relates to penis size! Bear with me a little longer and you’ll understand.) This is because men never really have certainty over their paternity, whereas women are always sure their offspring is theirs. Or as tribal people phrase it: “mother’s baby, father’s maybe”. This paternity uncertainty is why sex is so important to men, while it is just something of casual importance (although fun) for women. (From an evolutionary standpoint, women’s uncertainty is about whether they will be able to keep a partner that invests time and resources in her, or whether they’ll end up pregnant and alone, and potentially with a damaged reputation. Or in an equally horrible and catchy phrase: “this dick is for you baby, but my love maybe”. This is why weddings and marriage are such a big deal to women, because the social pressure this event creates on a man, makes it more difficult for him to step out.)

From an evolutionary perspective, men pass on an advantage to their offspring if they are a good father figure to their offspring, protect them and her mother and invest time in both. So investing time in their partner and offspring benefits the propagation of their genes, because insemination is only half the job. Getting a child to grow up successfully to make his own babies is the other part. (In support of the role of a father figure, data shows that men in prison more often used to be boys without a father figure than men not in prison.) For men, time spent on a child that is not genetically related, reduces the amount of time available for spending on a child genetically related. Plus, it imparts benefits to the genetic line of a rival at the expense of one’s own. On the other side of the coin, having another man unwittingly raise your offspring gives you the opportunity to double your “genetic output”. Men who unwittingly give benefit to the offspring of other men in comparison to their own offspring just don’t pass on their own genes that well into generations to come, whereas those that only raise their own offspring or have their offspring raised by others, pass on their genes extremely well. (Basically, women have created a selection pressure on men to be suspiciously jealous and to cuckold other men.) Thus, as a result all men are descendants of men that cared about dealing with rivals, and ended up with all kinds of pre-programmed ways to thwart rival men potentially taking a free ride on their partner. Men even end up attempting to thwart those men that were previously involved with their partner. (How many guys genuinely like the most recent and/or most attractive ex of their new intended long-term partner? Few. Worse, infanticide, i.e. killing of children, is much more common in men involved in raising children not genetically related, than in men raising their own genetically related offspring. The emotion driving this murderous behavior has unfortunately arisen in men’s evolution because it made sure these men did not help raise offspring of genetically unrelated men.)

The drive to pass on one’s own genes not only goes so far into modifying men’s (and also women’s) emotional responses and behaviors, but also physiology and anatomy.

One more example relating to evolution impacting behavior: our sex drives are most strong at night, and orgasm often induces a drowsy feeling, all because sleeping after sex ensures sperm will remain inside a woman’s womb long enough to impregnate her. People that only had sex during daytime and started walking about after each intercourse would have way less offspring or none at all, because the sperm would come right out of the vagina again. Our urge to have sex at night is a consequence of sleep cancelling out the leak out of sperm that would occur if women started walking upright right after.

The shape of the human penis,with its large glans (a.k.a. the dickhead) is different from any other animal, and in fact works as a mechanism that removes residual sperm from men that have recently had sex with the same woman. Interestingly, men suspecting their partners of just having had sex with another man have evolved to feel to emotional urge to having sex a.s.a.p., and they will insist on it, and even coerce their long-term partner if needed (marital rape). This all functions to make use of their penis as a sort of “vacuum cleaner” to remove residual sperm from the rival and replace it with a deposit of their own. Likewise, many sperm cells in a men’s semen are present not with the purpose to impregnate an egg cell, but rather to engage in sperm wars with sperm of other men. Even the viscosity of semen, how thick and sticky it is or how liquid it is, depends on the likelihood of the woman having intercourse with other men. Very liquid semen ensures the sperm cells have an easy times swimming upstream to the egg cells, but this kind of sperm is also easily removed by the “vacuuming function” of another penis entering a woman’s vagina right after, and runs out of her vagina way more easily if she stands upright after intercourse. Sticky semen makes it more difficult for the sperm cells to reach the egg cells, but is also less likely to be removed by the competing male that comes right after and less likely to leak out in case the sex has to occur during daytime. More and more evidence accumulates that the female orgasm is NOT just a byproduct of evolution, nor is it merely a means to increase bonding between man and woman. Orgasmic contractions of a woman actually bring semen to the ovaries. Thus men do have an advantage in caring for the woman’s pleasure. You may suspect THIS function of female orgasm lies at the base of men’s obsession with wanting to have a penis bigger than average. Yet, female orgasm is mostly facilitated by the circumference (the width) of a man’s penis, because primarily ‘a fat cock’ contributes to clitoral stimulation during intercourse via a process which is fancily labeled as labial tugging. It also contributes to the feeling of having something inside of her vagina. Yet, if width is accounted for, length may still have a role in compensating for some women’s anatomy and increase the chance of orgasm. One survey aimed at women found they more likely orgasmed without need for clitoral stimulation of a man’s organ was larger than average. Also, women with a shorter distance between the clitoris and the urethral meatus are more likely to achieve orgasm than women with a large distance between these two anatomical landmarks. A larger penis could compensate for the decreased orgasm likelihood in those women with a relatively large distance between these two structures. But it seems the primary evolutionary driving force behind the desire to “be bigger” lies in the competition with other men that may have sex with the same female. Even though women are afraid of being too tight and of pain during intercourse, having a penis larger than average ensures the semen is deposited outside of the “vacuuming range” of other men’s penises, regardless of whether the woman enjoys sex or not.

So there we have it! The desire to be large is driven by the desire to have women ‘suck up’ the sperm all the way to her ovaries on the one hand, and to deal with her potential promiscuity on the other hand. (Actually, the actual average penis size of any ethnicity is in direct proportion to the average likelihood of the females of that ethnicity cheating, because only those with larger penises produced offspring and and their semen was unable to be removed by rival males, whereas the semen of those with smaller penises was most easily removed from the place of deposit by equally or better endowed men.)

This also explains why guys check each other out: it is simply to see who could be serious competition. Those with a larger than average, and especially larger than the observing men’s penis, can deposit sperm out of reach, and have the potential for successfully putting a cuckoo’s egg in the observant’s nest. Guy’s need to know who is a threat, just to make sure with which guys chatting up their girl to be extra careful. (On the other hand, when the woman has sex outside of her relationship with a man that does not have any extraordinary endowment, it is sufficient for her partner to have sex with her right after, and his anatomy will do the rest in preventing insemination by the secret lover. So, even though large size doesn’t guarantee a guy will be more successful in chatting up an already “occupied” woman in comparison to “cuckoo guys” that aren’t endowed with extraordinary length, the threat of the former lies in the inability of the investing man to remove the sperm deposit and to prevent pregnancy.)

Virgin boys have concerns about the size of their penis because they want to figure out what chances they’ll make in passing on their genetic line in this game where their future partners will balance a fine line between a history and potential future of promiscuity and a promise of loyalty. They want some reassurance they are not in a disadvantaged position. For them it matters to know how their material compares to that of other guys during erection, simply because they’ve had never had feedback, and if their material is especially desirable regardless of his time investment in the woman, this puts him at an advantage. NOT disadvantage.

So finally: why do some studies indicate women don’t care about size? Well, the studies that find this are those that ask women about the importance of the length in their partner, not the penis length of a hypothetical fling with which she has no emotional attachment. The good news is that women perceive long-term partners as more attractive in proportion to the length of time since the onset of the relation, and this perceived attractiveness in turn facilitates her orgasm likelihood, large penis or not. Thus, regardless of penis size, with continued effort, you can still pass on your genes as a guy. In the end, all roads lead to Rome…


– On the subject of rape: although sex with multiple partners increases the odds of successful gene combinations, women still have to be picky as pregnancy and getting through the intense period of sleeplessness after birth takes a significant amount of time of her life during which she could have had offspring with a better mate.

– Before the advent of last century’s relatively efficient contraceptives, there was no selection pressure on desire to have offspring. It sufficed to have a desire for sex in order to pass on your genes. Perhaps in modern times, a high drive for sex alone is not sufficient to pass on the genes, unless one is occasionally careless about the use of contraceptives and/or unless one has an urge to have children.



Platek, S.M. and Shackelford, T.K. (2006). Female Infidelity and Paternal Uncertainty – Evolutionary Perspectives on Male Anti-cuckoldry Tactics. New York: Cambridge University Press.

Research articles:

  • Lever, J., Frederick, D.A., & Peplau, L.A. (2006) Does Size Matter? Men’s and Women’s Views on Penis Size Across the Lifespan. Psychology of Men & Masculinity, 7 (3), 129–143.
  • Mondaini, N., Ponchietti, R., Gontero, P., Muir, G.H., Natali, A., Di Loro, F., Caldarera, E. Biscioni, S. & Rizzo, M. (2002) Penile length is normal in most men seeking penile lengthening procedures. International Journal of Impotence Research,14, 283–286.
  • Puts, D.A., Dawood, K. &  Welling, L.L.M. (2012). Why Women Have Orgasms: An Evolutionary Analysis. Archives of Sexual Behavior, 41, 1127–1143
  • Eisenman, R. (2001). Penis size: Survey of female perceptions of sexual satisfaction. BMC Women’s Health, 1 (1).
  • Costa, R.M., Miller, G.F. & Brody, S. (2012). Women Who Prefer Longer Penises Are More Likely to Have
    Vaginal Orgasms (but Not Clitoral Orgasms): Implications for an Evolutionary Theory of Vaginal Orgasm. Journal of Sexual Medicine, 9, 3079–3088
  • Wallen, K. & Lloyd, E.A. (2011). Female Sexual Arousal: Genital Anatomy and Orgasm in Intercourse. Horm Behav. 59 (5), 780–792.

3 thoughts on “Penis size, part 2 – Why are men obsessed with penis size?

  1. Pingback: Penis size, part 1 – Buffing up! From small to supersize | braineggs

  2. Pingback: Penis size, part 3 – influences on length …and erectile strength | braineggs

  3. Pingback: Penis size, part 1 – How to drastically increase the length of your penis | braineggs

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