Hung like a gorilla

Now, I don’t want you to think that I’m bragging here, but human males have the largest penises of any primates. Not the largest in proportion, mark you, but the largest in absolute terms. A gorilla has a measly two inches. The super-sexy bonobos have penises closer to ours in length, but we easily beat them for girth. Why is this? In nature, whenever something is larger, brighter, more complicated, or downright weirder than it need be to get the job done then the betting biologist puts her money on female choice mechanisms as the likely explanation.

Picky picky picky

Peahen unimpressed by peacock
She's seen bigger

Darwin famously said that the sight of peacock’s train made him feel sick. He initially could not understand how such an over-the-top arrangement could possibly be explained by his theory of natural selection. Peacocks' trains make them conspicuous, slow, and almost unable to fly. How could the genes that build such a thing aid survival? Simple answer—they don’t. It turns out that mere survival counts for naught in this vale of tears unless you can persuade someone else to share those genes with you. That what peacock’s trains do—persuade peahens to share genes. Or, as we call it—have sex. Men are notoriously easier to persuade to “share” than women. Is this really true, and if so, why?

The great biologist Bob Trivers expressed it in terms of differential parental investment. Whichever sex invests the most in reproduction will be selected to be the more choosy about where that investment goes. In humans, the burdens of pregnancy, lactation, and childcare do not share out evenly between the sexes. Thus, human females—though by no means coy—are the choosier sex.

Note that is not an argument about the essential natures of males and females—it’s a strictly economic arrangement played out over millions of years. Whichever sex has the highest minimum investment in reproduction gets to be the picky one. In species like Emperor penguins, Mormon crickets and pipefish—where the males invest the most—they get to be picky and the females get to compete for their attention.

Not-so-blurred lines

Which brings me back to penises, and to female choice. Now, female choice mechanisms do not have to be conscious—and in most species they are not. However, the student of human nature has an advantage over his colleagues who study other species. We can ask our experimental subjects what they like. Often, they tell us. Sometimes, they tell us even without our asking. When they do, biologists have a marked tendency to see human behaviour in terms of its reproductive properties.

In these terms, Robin Thicke’s recent video Blurred Lines—especially the unexpurgated version—is a pretty standard piece of primate courtship display. He and his colleagues lay claim to a variety of things that they think might appeal to females. Among these are social dominance, height, attractiveness to other high quality females, wealth, and status. In addition to these—rather unsubtly at points 3:16 and 3:53—he claims possession of a large penis. In balloon letters several feet high the backdrop spells out the words—“Robin Thicke Has a Big Dick”.

There have been a number of imitations, parodies, and calls for this video to be banned on account of its heralding the collapse of western civilisation. I don’t want to talk about any of that. The response I want to focus on is the hilarious and instructive spoof by L. A. Comedienne Melinda Hughes. In case you haven’t seen it, here it is. Have a look—it’s worth it and will only take you four minutes.

As a response to Thicke’s courtship display, this video has many features of interest. However, I want to discuss only one rather glaring—at least to a biologist--feature. At no point in the video do the otherwise unimpressed ladies say that Thicke’s laying claim to having  a large penis is irrelevant to his potential attractiveness. Quite the reverse, in fact. Instead, at several points (1:03, 2:08, 2:56 and 3:43) they cast doubt as to the veracity of his claim. The ladies are, in effect, saying that you might have height, bling, and designer suits, but your behaviour does not impress us and, furthermore, we think that your penis is not what you claim it to be. We believe that it is probably "itty bitty" (2:56) and likely does not work properly (flaccid at 1:03, 2:08, and 3:43). In other words: You haven’t convinced us.

Melinda Hughes in small penis video
Melinda Hughes demonstrates female choice mechanisms in one species of primate


Now, in case you think that Hughes is simply trying to find a weak spot in the male ego to make the parody more barbed--here she is on the subject of penises again. In case you can’t access the video—Hughes engages in a three minute comedy barrage about why small penises simply will not do. The plural of anecdote is not evidence, you say? Let’s just say that what Hughes says here is not a surprise to those of us who study human sexual behaviour.

Just another critter?

But why is penis size a weak spot in the male ego? Essentially, the objects of desire of one sex become the battlegrounds of competition for the other. Men’s egos are attached to everything that they perceive to have fitness consequences, and they perceive much of this through the window of female behavioural preferences. As a mutually sexually selecting species females get lots of the same, but in reverse. Anything that anyone has lied to you about in a dating context is a good bet for being one of these battleground features. With human penises we have a unique situation—a crucial display item that we typically don’t display. At least, not directly. This makes for interesting behaviour.

So—why are human penises so large? Because human females have preferred them over evolutionary time and only the largest got selected. The ancient preferences remain. But--evolution has no foresight. Studies have shown that even partners of those with a micropenis can have a very satisfying sex life. It’s a good bet that such a person pays attention and tries just that little bit harder. These days--with modern prosthetics, oral and manual techniques, and various ingenious toys--the requirement for large penises to please sexual partners might be thought of as thing of the past.

Any caring and competent human should be able to generate an orgasm in their partner in a number of different ways. And if nothing else works, take Dan Savage’s excellent advice: Any models that do not come with oral sex fitted as standard should be returned to the showroom immediately—for a full refund.

However, our preferences do not always track our reason or, indeed, our interests. Humans have long sought for the source of human uniqueness—that special thing that separates us from all other animals. Well, I think I have a candidate. Uniquely, among all the animals, humans pretend that they are not one.

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