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More about penis evolution
March 10th, 2011
04:40 PM ET

More about penis evolution

By now you might've read about new research on the genes involved in  the evolution of the human penis. With more than 2,200 comments, our Wednesday story was a talker.

And it wasn't an excuse to say the p-word. Scientists have published a study in the esteemed, peer-reviewed journal Nature that happens to talk about penises. Specifically, they looked at DNA sequences among humans and primate relatives that basically serve as "switches" for other genes.

They focused on two switches that humans lack, but that chimpanzees have. One of these switches, the researchers believe, makes chimpanzees have whiskers and what they call "spines" on the penis. And the other relates to the brain - the absence of a particular DNA strand allowed the human brain to grow larger than the chimpanzee's, the researchers theorize.

But you didn't click on this headline, or the other one, to learn more about brains, now did you!

So, back to what you came here for. It turns out that there's some disagreement about the role of the primate male anatomy discussed in this research. As some of you noted in the comments, there are still many open questions when it comes to exactly how primates, including humans, evolved the way they did.

Yesterday, I had an e-mail chat with Christine Drea at Duke University, who studies mammalian social behavior and reproductive development. She sent me all kinds of detailed photos to illustrate differences in penis anatomy among primates. And there is a lot of variation.

In her view, the word "spines" may not be the right term for the small bumps that chimpanzees have. Other creatures such as cats have the more spike-like protrusions because the females of these species need appropriate stimulation from the male to ovulate. But primates ovulate spontaneously, so we wouldn't need spines for that purpose.

And, as I wrote yesterday, one idea about the function of the spines is that they can help the male pull out the sperm of another male that has previously mated with a female. But in chimpanzees and their relatives, their small bumps wouldn't be able to remove a competitor's semen in the same way, Drea said. In fact, chimps have unusually large testicles that produce large quantities of sperm, which do serve as a means of competition among males to get a female pregnant.

Also, in some primates, such as lemurs, sperm coagulates into "plugs" that can be pulled out with the spines; human semen does not do this, so we wouldn't be expected to have spines to remove it.

So, what are the bumps on chimp penises for? It's all speculation, but those of you (and there were many!) who joked about being "ribbed for her pleasure" may not be far off, as one explanation for the structures in chimps and other primates may be just that. They could be an "internal courtship device," Drea says.


soundoff (225 Responses)
  1. justsaying

    "...explanation for the structures in chimps and other primates may be just that. They could be an "internal courtship device," So Human females get less consideration in this regard than other mammals :^p

    March 11, 2011 at 14:10 | Report abuse | Reply
    • Neill Peterson

      Well, yes and no. That's a major function of the foreskin - if you still have it. The loose tissue allows the retention of lubrication, and a gliding, massaging motion.

      March 17, 2011 at 10:48 | Report abuse |
    • noname

      correction: some humans. My hubby DEF has a monkey penis.

      March 21, 2011 at 19:58 | Report abuse |
  2. Sheldon

    I find it funny when opponents of evolution take internal debates amongst evolutionists as evidence that the theory of evolution isn't reliable. All you have to do is look at the vast amount of evidence to see that various species have evolved over the years and that changes have taken place in response to environmental demands. However, this does not mean that there won't be disagreements between scientists about what evolved from what, or about which environmental changes spurred certain evolutionary changes. No reputable science willl reject the evolution as a scientific model, but this does not mean they will all agree on the details concerning every species.

    To say that disagreement among evolutionary theorists is proof of the falsity of the theory of evolution is like saying that disagreements among mathematicians about the nature of transfinite numbers proves that mathematics doesn't yield truths.
    But, of course, logic isn't the strong suit of "believers" in something other than evolution.

    March 11, 2011 at 14:12 | Report abuse | Reply
    • Bubba Schmo

      .... then there are those that are so convinced that evolution is a fact that they assume there is no other possible answer to how we got here. Even when there is no proof that it ever happened. Evolution is a theory, and if you buy into it hook line and sinker, you leave yourself blind to any other possible conclusions. Even the truth .... which, by the way, we may never know.

      March 11, 2011 at 15:45 | Report abuse |
    • david

      I can't believe I'm even replying to this. Only a scientific illiterate or someone who willfully denies evidence can consider evolution anything other than "proven." Furthermore, only a scientific illiterate can fail to realize that describing something as a "theory" is the highest compliment that can be paid to a scientific idea. It puts it on the same level as gravitation, which is still technically a "theory" but accepted as undeniable fact by virtually the entire human race.

      And, on the contrary, scientists are indeed open to evolution being disproved. It's just that nothing has come close to disproving evolution and offering a more reasonable explanation to the phenomena which evolution explains.

      March 11, 2011 at 16:15 | Report abuse |
    • brad

      Hey Bubba, gravity is a theory too. Now go jump off a bridge.
      Hey, electromagnatism is a theory. Now go stick your finger in an electric socket.
      The theroy of ballistics is just that, a theory. Go put a loaded gun in your mouth and pull the trigger.

      Yes, evolution is a theory. Because you see sir, until every possible variable has been eliminated nothing is a true law. Evolution is as real as gravity or any other science based idea. So, do the world a favor. Turn off you computer and your phone, dont eat the food or wear the clothes you have and that science has given you. Go read a real book, one that asks questions and actually looks for the truth. Not one that makes you afraid of the boogie man.

      March 11, 2011 at 16:20 | Report abuse |
    • donna

      Evolution isn't a theory, it's an observable fact.
      The Theory of Natural Selection is an observable, factually occurring process. (Theory also means- a string of facts that describes a process.)
      The Theory of Common Descent IS a theory (theoretical) about what happened in the past.

      March 11, 2011 at 16:32 | Report abuse |
  3. equality

    Geeez; ain't it amazing the rucus a penis can cause.. A Stiff Dick Has No Con-Science!?! I mean "Conscious" ..Or, was that; "Constraint" ? Hmmm.. Such "Contemplative" "Contempt" "Con-(s)-True'(d)" "Contaminate" "Consciousness" "Contadictory" "Contrived" "Contrast" "Contravened"... Hear? or, Here!(?)

    March 11, 2011 at 14:17 | Report abuse | Reply
  4. Snorlax

    lol dongs

    March 11, 2011 at 14:24 | Report abuse | Reply
  5. larrywi

    My thoughts just knid of petered away!

    March 11, 2011 at 14:39 | Report abuse | Reply
  6. CaMale

    WOW-hard to get over your obsession on the p-word Elizabeth. And I might add the pic you posted with the article the other day was ever so charming. I bet you looked at hundreds of penises of primates just to choose the right one. Aren't you special.
    I even bet you were in penis heaven with all those pics the researcher sent you. I for one could have done without your giddy attempt at humor and the pic was ever so precious. As a reporter or writer or author-personally? you leave a lot to be desired. I for one found your article crude, filled with the usual feminist humor directed at the expense of the male. Scientifically, iot was pathetic-and you have lost any respect I may have had in the past for you. I remain, Disgusted.

    March 11, 2011 at 14:47 | Report abuse | Reply
  7. mrbones

    Did someone really spend time trying to figure how a monkey peter evolved? really! Bunch of idiots. Nothing ever evolved into anything. Everything is as it has always been. If ours evolved, why are there still monkey peters? You folks just have it all figured out don't you? And so you got all that education to come down to this? really..................

    March 11, 2011 at 15:23 | Report abuse | Reply
    • idnar

      Typical uneducated response. Humans and other primates shared a common ancestor millions of years ago, humans didn't evolve from monkeys. As for why there are still monkey peters – well, there are still monkeys, that's why. There's an article in this month's Outside magazine which covers the evolution of species in the Chernobyl area that has occurred in the last few decades right before our very eyes. Evolution is a fact. Exactly how it works is still the subject of many theories.

      March 11, 2011 at 16:05 | Report abuse |
  8. jack

    Let's not forget the aboriginal Australians who insert pebbles under the skin of their penises thereby creating artificial "spines". That's got to be worth a mention if not a few photos.

    March 11, 2011 at 15:27 | Report abuse | Reply
  9. ess marques

    interesting

    March 11, 2011 at 15:40 | Report abuse | Reply
  10. jon

    I wish my dong would evolve! I'm been 5.2 since I was 12.

    March 11, 2011 at 15:53 | Report abuse | Reply
    • D

      That's something I could have gone all my life reading, Jon, thanks for sharing *eyes roll*

      March 13, 2011 at 21:30 | Report abuse |
  11. khalid mahdi

    I think it's interesting.....why ask shouldn't we ask about the penis....part of our evolution...??? we should be using more "head" power...the head on our shoulders....that ought to stimilate you......

    March 11, 2011 at 16:26 | Report abuse | Reply
  12. I wonder...

    So many detractors of creationism claim that the belief in it is somehow for weak-minded people; for people who aren't smart enough to think. It somehow invokes hatred towards those people who don't buy-in to evolution. It seems to me that this is simply a natural reaction by a mindset that is fearful of the possibility that a power greater than themselves exists whom created the DNA of moral law on the heart of every man and which draws each soul to be accountable to that law and thereby deny themselves the opportunity to justify moral relativism and apathy towards morality and justice in their own life. Because both viewpoints require faith, it is much easier for those seeking a non-accountable existence to vehemently defend evolution and fiercely attack the idea of a creator. I personally believe the debate between evolution and creation should not be a debate between science and religion. It should be a debate about "bad" science vs. "good" science. Creationism science may be very intriguing to those evolutionists with open minds. If you are interested, I highly recommend you reading, "I Don't Have Enough Faith to Be an Atheist" by Norman Geisler and Frank Turek.

    March 11, 2011 at 17:28 | Report abuse | Reply
    • donna

      The debate has been hinged on "bad" science vs. "good" science for a long time. There is an overwhelming amount of scientific evidence for evolution and none for creationism. 100% of the evidence supports natural selection and the theory of common descent.

      March 11, 2011 at 18:40 | Report abuse |
    • FaithNotFossils

      I agree with "I wonder"

      Sorry Donna but I've never seen any evidence for evolution – scientific or otherwise, let alone enough to be overwhelmed.

      March 12, 2011 at 00:13 | Report abuse |
    • donna

      Really? You don't believe that animals live and die?
      You don't believe that animals who reproduce, pass on their genes to their offspring, and animals that don't reproduce, don't pass on their genes to their offspring?
      And you don't need to apologize for not believing evolution exists. The beauty of reality is that it exists whether people believe it does or not. ; )

      March 12, 2011 at 01:35 | Report abuse |
    • FaithNotFossils

      Animals living and dying with or without offspring or the passing of genes is no more an iron-clad case for evolution than it is for creationism.

      The real beauty lies in that humans have debated this for hundreds of years and will continue to, hotly at times, until one day in less than the blink of an eye, we will all know the answer.

      March 12, 2011 at 19:27 | Report abuse |
    • donna

      Faith- obviously you don't know what "evolution" or "natural selection" are. Evolution is simply the change in gene frequencies in a population over time. So yes, those are examples of factual observations of evolution and natural selection. It might help you if you understood the terms you were using.

      March 13, 2011 at 13:42 | Report abuse |
    • FaithNotFossils

      Donna – You're right. Folks should know what terms mean if they are going to throw them around as though they are law (which we know is ever-changing.) And I must admit, you've done a fine job here playing Meriam-Webster's.

      March 13, 2011 at 17:45 | Report abuse |
    • hastingspete

      Here's my concern about whether people accept the fact of evolution or the fiction of creationism. There is simply no scientific evdience for creationism and the evidence for evolution long passed the reasonableness test. If you want to ignore science, go ahead. But if it means you then go and protest before Texas school boards and dumb down our text books and eliminate the basis for modern biology from our education system, you have American children growing up woefully unprepared for modern biology in the twentieth century. And that technology will move overseas and modern medicine will be forever damaged. Evolutionary biology explains everything about out bodies, from the role of germs to the functions of our organs and how and why we got to the way we are. Applied to DNA research, you can actually see where the jumps and breaks occured. THis isn't mystery. It's a puzzle being solved, and the results will change everything. And we will miss it if we dumb ourselves down refusing to believe in science.

      March 13, 2011 at 19:43 | Report abuse |
    • Thoughtful Discussion

      Evolution is right and wrong. Animals do naturally adapt to their environment over time such as bears adapting to polar environments or temperate forests. Natural selection does take place and is an observable fact in both the scientific community and even with in modern labs that study disease. But an adapted bear is still a bear. An adapted frog is still a frog. It is true that adaptations create new species but within limits. Science will not observe a frog transforming into a lizard, a lizard growing wings to reach prey, or rabbits turning into pure carnivores. Adaptation can only modify existing structures like a species of frog in the South Pacific that adapted the webbing on its feet to glide from tree to tree.

      What truly is needed is thoughtful discussion on evolution. What parts are observable and confirm able (adaptation)? And what is speculation or interpretations about the past that should be left up to scientists.

      March 24, 2011 at 23:26 | Report abuse |
    • scientist

      @Thoughtful Disscussion. You've obviously never taken an introductory evolution or genetics class. The theory of evolution/the theory of natural selection does not pertain to individual organisms but to a population. So while scientists have never seen a lizard grow wings but that doesn't mean evolution of a species does not occur.

      April 7, 2011 at 14:39 | Report abuse |
  13. Younan MarketingAnd Management Associates Inc, Int'l Intst'r

    My poor Fairy Queen female canary relapsed again, the tetracycline i was giving it in water i think went dead and i ran out.
    So next maybe better solution. Baking soda sprinkled in water feeder helped revive it again. I have to keep giving it that till it recovers from some intestinal and other infection that i think developed from all those problems, egg bound, allergy to seeds maybe poisoning, maybe other causes. I keep changing its boilded egg feed and peaches andother fruit. It will be ok on that until i find a seed option. Theresa Noelle Younan YMMA-III I-PIC Interpole Galactica Younan Research Management. The canary is sleeping and napping better now too. IT lost some wing strength but is starting to get it back.I had to let it sleep in my hands almost all week during it's sleep time. It couldn't stand well to sleep in its cage. its legs and feet were too weak then it would fall on its back and go into a paralysis type attack trying to get back up. Then I'd have to take it into my hand for care again. I think if a vet had to spend that much time on it it might have equaled $5,000 to $10,000. Because sometimes they don't give it what it needs right away either and you have to bring it back or leave it there or they lose it or they tell you to put it to sleep. Another mistake i made, because its legs and feet were weak it couldn't properly feed on the feeder not even with them at the cage bottom, i had to switch to a plastic flat lid for a feeder and then it ate a lot. Negative discussion about its health also damages it whether directly or away from it.

    March 11, 2011 at 19:27 | Report abuse | Reply
  14. Fred

    Evolution is only a theory. It has been reformulated many times over the years in attempts to cover all the holes and logical inconsistencies in the theory. Face it: species reproduce after their own kind. Imagine the embarrassment of a lizard that laid an egg and saw a bird emerge from it!
    Ah, you crazy atheists... I enjoy you guys so much!

    March 11, 2011 at 20:50 | Report abuse | Reply
    • donna

      Just what do you think evolution is?

      March 12, 2011 at 01:30 | Report abuse |
    • ScarletteBlues

      What's funny is that the people preaching creationism have no clue about evolution at all. They're only speaking what they've heard from their preachers. I encourage you to read a book, a simple text book.

      And who said God didn't create evolution?

      March 26, 2011 at 12:30 | Report abuse |
  15. Patrick2525

    Evolution is not an *Active* process, where a living organism consciously changes its body to serve a purpose. Its passive, where organisms that have a certain trait are able to live longer and/or reproduce more, and thereby that trait over time becomes prevalent within the species. To say stuff like 'the function of the spines...' is just absurd; a more accurate description would be 'the effect of the spines...'

    March 12, 2011 at 08:12 | Report abuse | Reply
  16. Vera

    An iPhone app that can save your life? That's right! The Breast Health GPS can locate the nearest mammogram screening center AND connect you to all the social networking sites of the Breast Health and Healing Foundation. It's the # 1 breast cancer app on iTunes! Take a look: http://itunes.apple.com/us/app/breast-health-gps/id361840350?mt=8

    March 14, 2011 at 00:08 | Report abuse | Reply
  17. Tisha

    I would like to point out that the "Creationism" theory, in my opinion, is flawed at it's core by the literal interpretation of the old testament.
    How many who ignore irrefutable scientific evidence have considered that perhaps, the story of creation was never meant to be taken literally and could in fact be allegory? Have they paused to consider the societal and cultural differences at the time the story was captured, second-hand at that? Or how often the Bible relies on allegory and metaphors to communicate a deeper meaning? Or even that perhaps the story of creationism could not have been told in terms that people at the time could understand? How does one explain the birth of a universe from a single particle to people who have no conceptual understanding science at all? If you went back a few thousand years and tried to explain the concept of gravity, just gravity how would you do it?

    If you can't wrap your brain around actual science and fact, try contemplating how other factors could support your religious views without completely throwing reality out the window.

    just a thought...

    March 14, 2011 at 03:37 | Report abuse | Reply
    • Slim

      A great thought it is. More people should be doing this more often. Just think about things for a minute....

      April 6, 2011 at 17:12 | Report abuse |
    • b

      sounds good to me, think a little, its good for you, but i think that we are forgetting the percentage of the population that does think is very small, the rest are followers, who only think what they are told to think.... which mainly includes religious groups, extremest and many others who are not smart enough to think

      April 18, 2011 at 17:41 | Report abuse |
  18. karek40

    When we look at the layers of earth we find practically a void of life in the fossil record until the Cambrian period when suddenly the earth was filled with all manner of life (fossil record). This is a major problem for Darwinian evolutionists. There was not sufficient time for evolution to develop the diversity of creatures; they all appeared in a relatively short period. The most recent problem confronting evolutionists comes from the field of microbiology. The tremendous amount of information stored in each cell clearly points to intelligent design. The problem scientists have is they cannot publicly take a position supporting intelligent design (that evolution simply can not explain what they are finding) with out being ostracized by those who simply refuse to accept the new information. I believe it was Max Planck who said; a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it. Most of the existing academia will have to die before the younger generation can accept the truth of intelligent design.

    March 14, 2011 at 14:15 | Report abuse | Reply
    • Atheist

      clearly...

      March 15, 2011 at 10:03 | Report abuse |
  19. bigrichard

    Mine "evolves" whenever a hot chick walks by.

    March 14, 2011 at 17:17 | Report abuse | Reply
  20. Karen

    Who Cares, If It's good do It , If it aint', Leave It !!!!!!!............

    March 23, 2011 at 21:47 | Report abuse | Reply
  21. Bruce

    A number of years ago I worked in primate reproductive physiology. My first project was to do some electron microscopy work on the morphology of baboon and human spermatozoa. It was interesting to me that most baboon spermatozoa were identical in morphology, yet the majority of human spermatozoa were of all sizes and shapes. These shapes ranged from double "necks" (can't remember the names of the parts of a spermatozoa since I've been out of the field for years), double heads, double tail pieces, small cells, large cells, etc. The shapes of the baboon spermatozoa were almost always identical in morphology. I always wondered why a clearly more advanced human would have such irregularly shaped cells whereas an animal who is supposedly lower on the evolutionary scale would have regularly shaped cells. Does this reflect some evolutionary advancement of humans over baboons? Perhaps a similar mechanism occurs with chimps and penis spines. Just an interesting observation by a young science major during his early career in the 60s.

    April 8, 2011 at 21:07 | Report abuse | Reply
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