The Surprising Role of the Shape of the Human Penis

And what my theory contributes to this finding

As I took my young sister to the salon, I couldn’t wait to continue reading the book by Jared Diamond, Why is Sex Fun?

It was a Sunday afternoon, and I was supposed to return to campus for class the following day. I barely noticed as time flew by — the perks of a good book.

The following morning, as I waited for the lecturer to come, I continued reading the same book. A classmate passing by my usual seating spot asked what I was reading.

It was a guy.

Well, from the title, you might think it is porn.

Now he was interested.

It’s Why is Sex Fun?

Immediately, he requested I send him the book.

Jared Diamond’s work is an interesting take on how sex takes a different perspective when viewed under the lens of evolution. It is insightful. But one question he never answers is the mystery of the human penis.

He talks about it, how it is longer and thicker than our closest relatives, chimpanzees, but never gives a preferred solution to the mystery. If reproduction was the reason people have sex, why does the human phallus differ so significantly from chimps?

My encounter with a 20-year-old study shows the reason is very intentional.

Four, five seconds from wildin’

Imagine we’re in the Savanna.

Homes are not guarded by ‘mbwa kali’ and no security guards. Estates are not conceivable, no one has thought of inventing gates or gated communities, and the daily routines include hunting and gathering.

Men would hunt and the women would gather food. Sometimes, one man would come home with a big bounty, enough to satisfy him and his family for a long time. If he’s generous, he could share it with other families.

The partner might want to celebrate the hunt by having sex. Before his big kill, the separation between the moment he went to hunt and when he came back is enough to have another man pounce on his partner.

There were no ‘mbwa kalis’ and security guards to stop a lady from having another sexual encounter with another man when the distinguished male partner was away. Let’s call this scenario one.

The second one is the man comes home, is well received, and even shares parts of his kill with other families. He has sex with his distinguished partner, but the other women also want a piece of him, they want a part of his success. It could also be that the women wanted to show their gratitude and could offer conjugal rewards for the generous gesture of the man.

These two scenarios are enough to explain the shape of the human penis. What’s more, you only need a single thrust for maximum effect. And a single thrust can last for four or five seconds.

Now I’m four, five seconds from wildin’ — Rihanna

With a single thrust, the shape of the penis allows it to displace whatever sperm deposits were in the vagina. It effectively says — I will go in, remove what might be inside, and then leave my deposit.

How?

The glans penis has a crown around it giving it a ridge underneath — the coronal ridge. This is connected to the tip of the penis using the penile frenulum at the center.

Suppose there were some bits of sperm by the time our successful bounty hunter came back. A single thrust by the opportunistic male will gather the contents using the thicker rim of the glans and force it up through the frenulum to land and accumulate around the coronal ridge. Continuous thrusts will continue to deposit the contents outside the vagina so much so that by the time he climaxes, he deposits his semen.

Modus operandi? Displace and replace.

Known as the semen displacement hypothesis, it has been well-tested and the results are surprisingly robust.

In scenario one, a man only needs to make the most of the little time with your partner to effectively deposit his sperm. A single thrust can potentially displace pre-existent vaginal semen with up to 91% efficiency. This should answer the question conjugal partners have always asked themselves — why did they get pregnant in a single shot?

I think I’ve had enough

You might think that if the penis was well shaped to displace sperm, shouldn’t it displace its own deposit?

Well, the physiology ensured that it doesn’t.

First, the penis has to be hard. Secondly, it becomes longer with erection. These two components highlight parts of the study supporting the hypothesis.

A hard penis ensures adequate penetration. It also engorges the glans for effective displacement. But the shape is not enough. The depth of the thrust has a role too. The workers showed that a three-quarter depth was not as significant as a full-on hundred percent thrust.

More semen was displaced with deeper penetration.

Even more, male partners who thought their women were having external affairs would have deeper and more vigourous thrusts. Infidelity, however, was not the only determinant of the depth and the force of every penetration. Separation was enough.

For couples who reported not seeing their partners for a while, the outcome was the same — deeper and more forceful sex. The hypothesis is consistent with the idea of semen displacement.

The men echo what Rihanna sings:

I think I’ve had enough, I might get a little drunk

Drunk with the idea that somebody might be cheating.

It is similar to the stories of make-up sex we tend to hear. Couples tend to describe it as different from the other kinds of sex. The semen displacement hypothesis could explain it.

But even more, it assures the male that it is their sperm that stands the better chance of fertilizing the woman. We have talked about the erect state and the lengthening. The third is the refractory period.

This is the period when the penis becomes limp after ejaculation. It works to ensure only the deposition of one’s semen, after having effectively displaced the previous possible seminal contents.

Collectively, the erect penis displaces, and the limp one, after ejaculation, deposits.

Neat, huh?

Now, my theory adds to this idea

The theory of Organismal Selection is pretty simple.

It states that an organism will always tend to avoid annihilation. It will do anything to achieve this. The easiest option is to seek mergers. So a gene will merge with another to eventually form a genome. The genome will merge with organelles to form a cell. A cell will merge with another to form a unique domain in biology. The cells will merge to form multicellular entities…you get the gist.

Size then becomes an inevitable topic. With every merger, size increases. The effects of increasing size are subtle, yet profound once understood.

Since mergers result in an increase in size, understanding the different types of mergers is an insight into understanding the offshoot effects of size. The simple way to increase in size is through producing more. A business will scale the more it produces. Sperms, once they have started being produced, will continue the process inside the man until he dies.

A one-to-one comparison between a sperm and an ovum shows how small it is compared to the cytoplasm-rich female gonadal product. As far as their numbers go, however, you can see the product of many sperms in an ejaculate. You cannot, however, see an ovum once it is extruded from the ovary. This is the size I refer to.

It’s like the members of a species who continue to reproduce so that at least one of them survives the untold adversities of the future — it is an increase in size through numbers but not volume.

Size, through numbers, increases the chance of an organism outlasting others before it dies. The number of sperms in an ejaculate is no different from species — one of them will try to find the ovum and continue the legacy of the other sperms.

Bearing in mind what we have already discussed, the numbers game favours the person who last deposited his sperm in a woman, provided the egg was not already fertilized. Playing the numbers game, the fresh ejaculate has a higher probability of fertilizing the egg than the ejaculate it had displaced.

Size, once more, comes to the rescue.

Displacement, deposition, and numbers work in favour of improving the rates of fertilization. However, the fecundity rates — the probability that a woman having unprotected sex will conceive during an ovarian cycle — are low among human beings for reasons that are evolutionary unknown.

Where does that leave us? Too much displacement? What then is the role of sex in humans? There is a lot we assume.

What I’m trying to say is…

According to the semen displacement hypothesis, the shape, thrust depth and the after-effect of ejaculation work together to ensure the successful outcome of a sexual encounter.

The numbers game, a different way to look at the size, works in favour of all these mechanisms.

The theory of Organismal Selection talks much more, however, about how organisms survive. Size is one of the four S’s I use to explain the theory. The other three are statistics, symbiosis, and self-organization.

Now, please forgive the pun, but I’ll let you think hard about this.

Then you can come to your own conclusion.

Pun intended.

PS: If you want to get an e-copy of my book which is an extensive discourse into my radical theory of evolution and a better understanding of what I have discussed, you can find it here.