What Evolution Tells Us About Penis Size
Many men with larger-than-average penises think size is important, while many with smaller-than-average penises
think it’s irrelevant. Women, on the other hand, are an unknown quantity.
Some say size doesn’t matter, as long as they love the man to whom the penis is attached. Others are adamant a
relationship can’t work if a man is too small to satisfy them. So what does evolution tell us about penis size – or
the lack thereof?
Men who have what they assume to be a smaller-than-average penis can get quite touchy about the subject,
particularly if it’s a woman who points out their shortcomings. After all, penis size is meant to be a reliable
indicator of virility and masculinity, both of which are inextricably linked to a man’s sense of self-worth.
On the other hand, a man who is praised for having a larger-than-average penis is likely to be very pleased with
himself. The mere suggestion that he is generally bigger than other men can make him irresistible to some members
of the opposite sex, and create a persuasive (but probably faulty) illusion about his sexual capabilities.
Before moving on to the evolutionary aspect of penis size, it’s pertinent to
point out that, as yet, there is no conclusive verdict on an average size. Research shows that averages vary
according to race and sometimes even nationality.
Conventional wisdom suggests an erect penis of between 5.5 and 6.5 inches (14 and 16.5 centimetres) is average,
while, for the purposes of this article, anything below 5 in (12.7 cm) and above 7 in (17.8 cm) is regarded as
small and large respectively.
The mere fact that having a large penis is so desirable means it should, theoretically, be favoured by
evolution; in other words, each generation of men should be growing larger penises.
Based on this logic, if women rejected men with small penises, there would be fewer boys born with this
anatomical shortcoming, and more being born with large penises. But if this were the case, there would still be the
same variation in penis size, as everybody would be growing.
To add another dimension to this argument, a woman who falls in love with an unattractive man is unlikely to
dump him on the basis of a small penis. This makes the natural selection of penis size in humans an extremely
To get to the root of the matter, it is necessary to analyse the anatomy of our closest relatives, bonobos,
chimpanzees and gorillas. Male gorillas have small penises and testes because gorilla society doesn’t encourage
active sexual competition between males.
The dominant gorilla has a harem, which he alone is permitted to inseminate. There is limited opportunity for
other males to mate with females, so a large penis isn’t as important as a powerful, intimidating physical
Bonobos and chimpanzees have a different system. Their societies are more matriarchal, and the females have much
greater freedom to mate with any males they choose. As a result they copulate with multiple males, so the battle to
fertilise the egg takes place between sperm inside the female rather than externally between the competing males.
Males with longer penises can deposit their sperm deep inside the
female, and so win the sperm warfare by fertilising the ovum first.
Humans take this a step further. Unlike modern society, where monogamy is encouraged and women who ‘play the
field’ are frowned upon, our female ancestors were permitted far more sexual freedom. Pleasure became an important part of copulation, so penis size was doubly
important: not only did the male with the larger and longer penis get to deposit his sperm more deeply than his rivals’, he could also give the woman more
pleasure, so she was more likely to welcome him back for more.
This alone could explain why a modern woman may be predisposed towards a larger penis; not only is it
theoretically more likely to impregnate her, but it is also more likely to give her more pleasure than a small one.
In reality, however, there are too many variables at play to determine an individual woman’s preferences. Indeed,
many women report discomfort if their partner’s penis is too large.
Yet while there are overwhelming evolutionary similarities between humans and chimpanzees, there are also vast
differences. Unlike primates, humans are able to make judgments based on several factors other than penis size.
If a woman falls in love with a man with a small penis, she is likely to weigh up several other important
factors such as stability, shared interests and personal compatibility, before accepting or rejecting him.