How the (human) penis lost its spikes
March 3, 2015 7:05 PM   Subscribe

We're beginning to understand the genes behind how men lost their dick spines. In fact, smooth penises are a derived state in humans; many if not most mammals have some level of spikiness or roughness on the penile tissue. We've known that chimps have penile spines since 1944! However, no one's really quite sure exactly why humans lost their spines.

In addition, penis spines are by no means unique to mammals. They are very common in insects, fish, and they even occasionally appear in birds--most of whom have no penises at all! While in some species these spines may serve primarily to remove other males' sperm from the vaginal tract, in many they seem to be used in sexual conflict to bypass female defenses. Of course the most pronounced example of this is traumatic insemination. (Previously.)

However, while we understand a surprising amount about the evolution of penile morphology, we understand very little about vaginal and vulval evolution. (It's worth mentioning that the full structure of the human clitoris didn't get a thorough scientific description until 1998.) This is a shame, given how important the story of female evolution is to the story of the evolution of sexual conflict.
posted by sciatrix (58 comments total) 45 users marked this as a favorite


 
Gah! GAHH!!!
posted by Orange Dinosaur Slide at 7:11 PM on March 3, 2015 [13 favorites]


I wonder if the Dan Savages of the world will notice that these findings corroborate evidence on the evolutionary adaptation of humans to create more--not less--monogamous relationships.
posted by yellowcandy at 7:15 PM on March 3, 2015 [5 favorites]


However, no one's really quite sure exactly why humans lost their spines.

Reproductive advantage, perhaps?
posted by snuffleupagus at 7:16 PM on March 3, 2015


Cats. This is part of the reason cat mating sounds the way it does.
posted by fluffy battle kitten at 7:16 PM on March 3, 2015 [4 favorites]


You lost yours? Pity.
posted by Parasite Unseen at 7:18 PM on March 3, 2015 [39 favorites]


While in some species these spines may serve primarily to remove other males' sperm from the vaginal tract

I saw a thing--maybe even linked here--that showed the actual shape of the human penis serves almost as a vaccum-pump kinda thing that sucks other semen out of the vagina during thrusting.
posted by feckless fecal fear mongering at 7:26 PM on March 3, 2015 [1 favorite]


I want "Dick Spines" to be a new character on Better Call Saul.
posted by j_curiouser at 7:31 PM on March 3, 2015 [13 favorites]


So those demons in the Buffy Season 6 opener were closer to the norm than I thought.
posted by Jpfed at 7:33 PM on March 3, 2015


The best thing about being a human female after 1965 is the control of ones reproductive destiny — and the absence of dick spines. Pain and sex separated firmly.
posted by dame at 7:37 PM on March 3, 2015 [4 favorites]


I saw a thing--maybe even linked here
Indeed you did. The link has rotted but there is an article here (don't know if it's the same as the original). - Penis Enlightenment: Bering Straight Talk.
posted by unliteral at 7:42 PM on March 3, 2015


Chimps have a built in French Tickler? And we think we're more highly evolved...
posted by Brodiggitty at 7:44 PM on March 3, 2015


Penis/spine is a mesmerizing anagram. Penis spine penis spine penis spine.
posted by gatorae at 7:48 PM on March 3, 2015 [30 favorites]


It's proof that God loves us and She wants us to be happy?
posted by CBrachyrhynchos at 7:54 PM on March 3, 2015 [9 favorites]


Gaahhh! There's got to be a joke I can make about this but I got nuthin.
posted by zardoz at 8:10 PM on March 3, 2015 [1 favorite]


You lost yours? Pity.
posted by Parasite Unseen at 7:18 PM on March 3


Epenisterrorcal?
posted by lalochezia at 8:10 PM on March 3, 2015 [11 favorites]


Great, now the Men's Rights groups are going to be angry they lost their penis spikes too. Or maybe they are primitive enough to still have them.
posted by nickggully at 8:14 PM on March 3, 2015 [9 favorites]


Seems to be a rash of penis-oriented articles on the internet lately. The length of the penis, the history of the penis. Know your penis. Care and feeding of your penis. I am Joe's penis. A veritable orgy of penis-centric penis concerns. Could be my own pattern recognition in overdrive, but I don't generally worry too much about penis-related things. It's not a subject that interests me beyond the basic level of having to carry one around on a regular basis, and being interested in a general way in how to care for it. Just health issues, really. I'll carry this seven inch son of a gun to the grave with me, but I'm not going to let it dicktate how things are going to go in the meantime. That would be phallacious.
posted by metagnathous at 8:18 PM on March 3, 2015 [5 favorites]


I wonder if the Dan Savages of the world will notice that these findings corroborate evidence on the evolutionary adaptation of humans to create more--not less--monogamous relationships.

Is this some sort of attempt to slam those of us who aren't serial monogamists? You have basically the entire weight of cis-het culture behind you; is Dan Savage really so threatening?
posted by sevenyearlurk at 8:25 PM on March 3, 2015 [8 favorites]


Humans losing the baculum - aka the penis bone - and its relationship to penis spines and penis evolution must be tied together. Our closest ancestor, the chimp, has both spines and baculum, though small. The female equivalent of the penis bone - the clitoris bone, or baubellum is also present in chinps, but similarly lost in humans. Of the spines and bones, what was lost first? Did males and female lose their respective bones simultaneously or asynchronously? It sounds like bones first, since ~30% of males do develop a kind of remnant of the spine, called pearly penile papules. Why? When? How did replacing the baculum & baubellum with blood affect brain evolution? (I imagine the evolution of genitalia and brains, especially as it related to social development, is intertwined and connected together...well, like a double helix.)

Tracing all of this in terms of our social evolution is extremely hard for multiple reasons - behavior is always difficult, but there's some taphonomic reasons too. There's only a few cases of finding primate fossil bacula as it's the kind of bone that gets separated from the rest of the body easily (no jokes) after death. But we do know that our primate hominid ancestors still had bacula in the Eocene, ~34 million years ago. We also know there's been tremendous climate change since then and since climate change is a primary driver of evolution, it's also fascinating to ponder how penis spines, clit bones, and penis bones and their subsequent loss could be related to not just social/brain development of hominids but - perhaps - also as a response to climate. . . or both! All together - brains, bones, and behavior - there's a fascinating story that we're just starting to explore.

For those really interested, I can't recommend Dixson's book Primate Sexuality enough.

Great post, thanks! There's some really intriguing links in there.
posted by barchan at 8:26 PM on March 3, 2015 [23 favorites]


This is a great post, but I'm sitting in Phoenix airport on a layover between delayed flights, and all I can think of is that Boingo Hotspot is going to be surprised and horrified by the incidence of "Penis Spines" and "Penis Spikes" in their logs.
posted by RedOrGreen at 8:32 PM on March 3, 2015 [7 favorites]


a rash of penis-oriented articles

I see what you did there.
posted by Greg_Ace at 8:35 PM on March 3, 2015 [3 favorites]


I lost my part, in San Francisco...

I attended a lecture once about the differences betweem circumcised and uncircumcised men. I was told the foreskin conceals semen and a man who has a married female lover, can impregnate his own wife with his lover's, husband's semen. I realized then, the foreskin helps create more potential for genetic variation.

This is my tuppence, Spike.
posted by Oyéah at 8:36 PM on March 3, 2015 [2 favorites]


I swear some people would lose their heads if they weren't attached.
posted by If only I had a penguin... at 8:47 PM on March 3, 2015


Humanity, notable among terran species for their spineless dicks.
posted by otherchaz at 8:51 PM on March 3, 2015 [15 favorites]




So...the simple answer: 'because none of the ladies would have sex with them' isn't going to make the theory bracket? C'mon, it's got to be there somewhere.

"Psst. I hear that Lunkhead over there has a smooth one!" "Oh, do tell me more...."
posted by amanda at 10:00 PM on March 3, 2015 [7 favorites]


dame: "The best thing about being a human female after 1965 is [...] and the absence of dick spines."

So it's a recent evolution?
posted by Joakim Ziegler at 10:20 PM on March 3, 2015 [2 favorites]


Dick Spines, erstwhile centre-forward of the 1955 Leeds Utd football team.
posted by GallonOfAlan at 10:45 PM on March 3, 2015 [5 favorites]


Seems to be a rash of penis-oriented articles on the internet lately

I dunno, I feel like at upwards of 80% of it has been penis-oriented since at least the 90s.
posted by No-sword at 11:53 PM on March 3, 2015 [2 favorites]


So on my facebook feed there is a trending item

BJUI: British urology journal publishes study on average penis size based on over 15000 measurements

And I'm a little disappointed that no one in the trending item's feed has noted that, aside from being studied by the BJUI, a penis is literally a BJ UI.
posted by Jpfed at 12:06 AM on March 4, 2015 [10 favorites]


"Why does it have pinchers?"
posted by maxwelton at 2:19 AM on March 4, 2015


The human penis once had spines
The dick was prickly like a pine
You could lose an eye, doing 69!
That's how the penis lost its spines





(If you've ever seen Song of the South, please imagine this sung to the tune of Uncle Remus Said.)
posted by Ursula Hitler at 2:30 AM on March 4, 2015


nickggully: now the Men's Rights groups are going to be angry they lost their penis spikes

We hunted the mammoth with our spiky penises.
posted by tykky at 2:54 AM on March 4, 2015 [4 favorites]


I'm not sure when or why it happened, but I am certainly glad it did.
posted by louche mustachio at 3:11 AM on March 4, 2015 [1 favorite]


So you're saying these days dicks are pointless?
posted by kinnakeet at 3:55 AM on March 4, 2015 [7 favorites]


Could be my own pattern recognition in overdrive, but I don't generally worry too much about penis-related things.

Worried? Nah. Curious? Yes! And I don't even have one! (Maybe that's why I'm so curious!)

So, needless to say, this is FASCINATING to me. There used to be a penis BONE?!?! I too would like to subscribe to the newsletter that brings me such delightful facts.
posted by chainsofreedom at 3:55 AM on March 4, 2015 [1 favorite]


Human penises are larger, relative to body size, than our cousins (Gorillas get just 1.5in). Is it possible that the real adaptation was the increase in size, and losing the spines a necessary side-effect?
posted by Leon at 3:58 AM on March 4, 2015 [1 favorite]


Fascinating post, thanks sciatrix! And thank you as well to barchan; chanting 'pearly penile papules' is quite soothing.
posted by h00py at 4:12 AM on March 4, 2015 [3 favorites]


Human penises are larger, relative to body size, than our cousins (Gorillas get just 1.5in). Is it possible that the real adaptation was the increase in size, and losing the spines a necessary side-effect?

If only they were internal and could be extended with the right muscle flex, Siberian bear hunting suit style. It would be a great party trick, although of course no one would ever want to sleep with you.
posted by Dip Flash at 4:33 AM on March 4, 2015


I'm picturing all the mefis with penises checking themselves out based on some the info scattered about there.

At the breakfast table.

When they think no one is looking.

I'm picturing this. For a friend.
posted by clvrmnky at 5:08 AM on March 4, 2015 [1 favorite]


"Scott Bacula: Devolutionary Porn Star"
posted by grumpybear69 at 5:10 AM on March 4, 2015 [1 favorite]


We've known that chimps have penile spines since 1944!

And you thought that the GERMANS conducted strange experiments in the name of winning World War II.
posted by delfin at 5:15 AM on March 4, 2015


Pain and sex separated firmly.

You do sex your way and I'll do sex mine, thank you.
posted by Mrs. Pterodactyl at 5:40 AM on March 4, 2015 [9 favorites]


Know your penis.

Meet and greet!
posted by echocollate at 5:47 AM on March 4, 2015 [1 favorite]


the foreskin conceals semen and a man who has a married female lover, can impregnate his own wife with his lover's, husband's semen.

The SVU episode practically writes itself!
posted by lwb at 6:41 AM on March 4, 2015 [7 favorites]


I wonder if the Dan Savages of the world will notice that these findings corroborate evidence on the evolutionary adaptation of humans to create more--not less--monogamous relationships.

Yes, because human monogamous relationships are so endangered by Dan Savage and his wicked words!
posted by blucevalo at 6:52 AM on March 4, 2015 [1 favorite]


Penis/spine is a mesmerizing anagram. Penis spine penis spine penis spine.

our hotdogs / hurt so good
posted by argonauta at 7:24 AM on March 4, 2015 [9 favorites]


barchan I wish to subscribe to your newsletter.

I don't know if you do, I went to sleep last night wondering if basic language developed so that everyone could gossip about who had the smallest spines on their penis.

(Smaller spines = better sex = more sex = smaller spines gene gets passed on, ergo language development and penis spine loss are related. It totally works!)
posted by barchan at 7:39 AM on March 4, 2015 [2 favorites]


It's nice that the "how" in this case actually involves some molecular biology, but I think attempts to answer the "why" is going to be fatally limited by the relative scarcity of hominids to contrast ourselves with. If we ever complete the process that started with in the paleolithic and emerge as the last surviving member of our family, we will have lost to a great degree the ability to understand our own evolutionary history.
posted by CBrachyrhynchos at 7:50 AM on March 4, 2015


Metafilter: fatally limited by the relative scarcity of hominids to contrast ourselves with.
posted by grumpybear69 at 10:03 AM on March 4, 2015 [7 favorites]


One assumes this is the origin of the term "self-abuse" for masturbation.
posted by yoink at 10:17 AM on March 4, 2015


Gives the conflict between itchy and scratchy a whole new thrust.
posted by Namlit at 12:15 PM on March 4, 2015 [2 favorites]


what if you found some in the lost and found? would you give them back to their rightful owner?
posted by ChuckRamone at 12:26 PM on March 4, 2015


requires some spine to do that i guess
posted by Namlit at 12:35 PM on March 4, 2015


Can one assume that a spiky penis is where we got the nickname "prick?"
posted by Quasimike at 1:24 PM on March 4, 2015


Pain and sex separated firmly.

Well that's no fun.
posted by malapropist at 8:47 PM on March 4, 2015


So you're saying these days dicks are pointless?

me and my arrow
posted by emptythought at 11:49 PM on March 4, 2015 [1 favorite]


No, sevenyearlurk and bluecevalo, that's not at all what I was saying. I'm not interested in policing anyone's behavior in or outside the bedroom.

What I am saying is that Savage gets lots of mileage out of pseudo-scientific platitudes about how humans aren't 'naturally monogamous,' and this study demonstrates real evidence that that's actually the opposite of the truth.
posted by yellowcandy at 10:39 AM on March 5, 2015 [1 favorite]


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