penis size and evolution (semen displacement theory, etc.)

[petite]

What evidence is there for this? I am very skeptical that at any time in history a woman or women in a family did not influence who the young women would marry. As to their choosing to have sex with others than their husbands, obviously they do.

Obviously. I can see that you're skeptical.

Might just be attention from very dull husbands. This would then be part of the adaption cycle where a femal chooses a boring but powerful male to keep off unwanted suitors, but a handsom stud to actuallly mate with. Now an interesting adaptation would be one for not getting impregnated after unwanted sex.

What does this have to do with physical arousal caused by fear? A dull husband causes terror in women? What?

So who knows if by historical standards we do have large penises? They may have been shrinking for millenia. This might explain the current wide range.

Interesting thought, but an irrelevant idea when referring to what you quoted, which is in reference to man's current size compared to the relative size of other primates.

You mean surgical implants and corset shrunk waists? Not exactly genetic adaptations. Women are far more likely to be round than hourglass as far as waist goes. The hourglass waist is a classic male trait. (as is the muscled chest).

What? You haven't noticed that women grow breasts at puberty and their hips grow wider?

Muscular men have small hips and wide shoulders. That's not an hourglass. That's a triangle. Or a trapezoid. Not an hourglass.

Your nitpickiness misses the point, but I suspect that you just like to shoot things down and you're having fun doing it, even if it doesn't convey any ideas.

Any proof of this? How many million years worth of archive material has been read through? There may be a lot of publicity now for human fleshlights, but as a proportion of the total number of females is this reallly true? It is what is happening to the majority which counts.

I hear Google maps can find the library closest to you, but there aren't million years' worth of human history to read through.

So a woman has two men. One ugly one to protect her and one pretty one to have sex with. The ugly one is allowed in bed sometimes to keep him willing.

Interesting. You see proto-human females as mastermind puppetmasters who keep harems of men for procreation and protection? I'm exaggerating, of course. It was just an amusing idea. :tongue:

But suppose these are evolved to form a defense against alien sperm? To what extent has the ability of these so called deformed sperm been studied for ability to block any competitors which may be arriving later? Evolutionarily speaking, having a majority of defensive sperm never intended to impregnate might be very helpful.

They're not defense sperm. They sad sperm that don't function the way they're supposed to. This is an interesting idea, but there's no evidence supporting it.

Surely proof that it is not true. If he reacts that way now, why would other males not have had the same reaction at the time? And not done it.

Using that reasoning no one ever does anything wrong and our prisons should be empty and the nightly news should be boring. You make it sound like Rwandan genocide or The Holocaust never happened. I find it horrific, so those things didn't happen because someone else wouldn't do those things. Children getting their limbs chopped off for blood diamonds doesn't happen. Gang warfare and kidnappings over petty amounts of cash in Mexico don't happen. Violent gangs of homeless street children in Rio don't exist. Rape, murder, assault are all non-existent. The Vikings cuddled their enemies to death? I know you aren't that naive.

 

[petite]

It is the relative frequency of genes which changes and causes dramatic physical changes. So if you have the full set of small penis genes, its tiny. Full set of genes for big, its huge.

Yes, true. I don't understand how this is a response to what you asked about how we know when certain evolutionary changes occur. There's a molecular record in our genetic code and that code says that in the past 10,000 years there have mostly been changes in proteins and enzymes. In a genetic pool as large as humans have, it takes a long time to affect a major change in the frequency of large or small penis genes.

This isn't an argument for or against recent change. Some changes can occur quickly, depending on the circumstances. There just isn't any evidence that it's occurred more recently, not that I've seen. Lack of evidence for it doesn't mean it didn't happen, but science doesn't work in the inverse like that. There's no evidence that unicorns don't exist either.

But genetically they are identical. Either these apparent behaviours have absolutely nothing to do with genetics and chances of inheriting traits so this whole discussion is pointless, or there is an underlying behaviour which is genetically determined, does matter, and has not changed. In thinking about inherited anything, we are only interested in genetically determined behaviour, and by definition this is unchangeable unless the genetics change. If we can identify a genetically inherited trait now, then it also existed 50, 500, 5000... years ago.

Yes, I was responding to your insistence that women in the past acted the same way that they do today, when they didn't even act the same way 50 years ago.

Our social behavior influence our genes, if it continues over a long period of time. That's sexual selection, regardless if that social behavior is genetically encoded or not. It still causes evolutionary changes.

Recently, women have gained a lot of equality, and that will influence our genes in the future. More than likely, men will become more and more attractive, since women have more selective power than they did in the past and women are selecting based upon "sexiness" now since women have more economic power and can choose based upon other criteria.

Then invent the gun. and the laser gunsight. and the automatic tracking system....How huch muscle power does it take to type in a command?

This is irrelevant to whether or not proto-humans used tools that needed strength as well as skill to make them useful.The original point was that the gender with the selective power has the practical body, like men have. Women have breasts before they bear young, which makes us totally unique and it's obviously a trait selected for by men. Women's bodies are small and sparsely muscled, which also seem to be features men select for. Men on the other hand are faster, taller, and stronger and built for practical physical tasks.

Of course men like to think their cocks make them the peacocks, waving them around hoping that a woman will choose them to mate with. The problem is that there's more evidence that women were sexually selected for and there's the lack of evidence that women choose men based on cock size. There's no evidence that women prefer larger dildos or vibrators, as I mentioned earlier. That's easy to check out. Just go to any online sex shop where women leave lots of reviews. The highest rated ones are all"average" size. Big ones aren't popular and get lower ratings because of complaints about being too big. Not even on Fetlife do the large cock groups get a lot of female traffic, and those women are the kinkiest women on earth. Those groups are pathetically small, consisting of a few hundred members and dead, too, so not even the fetishy women are into big cocks.

And what about LPSG? If women really selected based on cock size, making men the peacocks, then this board should be chock full of horny women competing for the attention the men here. All these hung guys should be swimming in more pussy than they can handle, because a lot of these guys are in the upper 5% for size. Unfortunately, there's a lot of threads where straight guys talk about their problems hooking up with women, and a lot of virgins here. LPSG can barely keep 100 women around. That doesn't support the assumption of men who believe in sexual selection by women for cock size.

So why are men so obsessed with their penises, to the point that they assume women are, too? Well, maybe men are supposed to be, because maybe that was a lot more important once upon a time. I don't know if that's true, but having been a member of LPSG for a while now, I've asked myself that "why" question a lot.

 

[dandelion]

What does this have to do with physical arousal caused by fear? A dull husband causes terror in women? What?

You did not specify before that it was an arousal response to fear, merely becoming physically aroused without being mentally aroused.

Interesting thought, but an irrelevant idea when referring to what you quoted, which is in reference to man's current size compared to the relative size of other primates.

I would think that if there is currently a wide variation it suggests that currently there is no real presssure to any preferred size. However the existence of genes for giant size may mean that in the past there was such pressure. Though having said that, I note the current human average is still significantly larger than what is strictly necessary. So perhaps there was some historical point when this was quite important.

What? You haven't noticed that women grow breasts at puberty and their hips grow wider?

I'm gay, right? Guys have waist size smaller than hip size hence hourglass waist. Or they would if almost everyone nowadays wasnt overweight.

Your nitpickiness misses the point, but I suspect that you just like to shoot things down and you're having fun doing it, even if it doesn't convey any ideas.

Of course I am having fun, why are you here? But I write it as I see it. If you try to do genetic theorising without nitpicking you will fail.

Interesting. You see proto-human females as mastermind puppetmasters who keep harems of men for procreation and protection? I'm exaggerating, of course. It was just an amusing idea. :tongue:

Yes, of course. Why bark yourself if you keep a dog.

They're not defense sperm. They sad sperm that don't function the way they're supposed to. This is an interesting idea, but there's no evidence supporting it.

Cant tell you where to find it, but there is.

Using that reasoning no one ever does anything wrong and our prisons should be empty and the nightly news should be boring. You make it sound like Rwandan genocide or The Holocaust never happened. I find it horrific, so those things didn't happen because someone else wouldn't do those things.

You arent the only one to find this horrific, yet it happened. Yet people object to it. Some fore, some against. Why would this be different in the past? I doubt most of those involved in any particular atrocity were rabid supporters of the idea, they just went along with a crowd. Which is the point. Bad things happen but although they may never object, people dont necessarily agree with them.

Children getting their limbs chopped off for blood diamonds doesn't happen.

I am relieved to hear it. Must agree though it certainly never jhappened to anyone I know, and did not happen to 99.9999999....% of children in the whole world. These are exceptions you are quoting.

The Vikings cuddled their enemies to death? I know you aren't that naive.

I saw a TV program in the last few weeks which said most vikings were peaceful stay at homes who never did anything to anyone. But some were not. It is a perception they were all rutheless bastards, which obviosuly is not true if you consider they are the same racial stock as us.

 

[dandelion]

In a genetic pool as large as humans have, it takes a long time to affect a major change in the frequency of large or small penis genes.

There are quite a lot of humans now, but the number is vastly bigger now than in relatively recent times.If you mean there is a wide range of individual genes, well maybe so but the pressure to change depends on the survival value of each one. If one suddenly infers a big advantage then it will spread rapidly. Population change is generally the drawing out of traits which already existed within a population but which suddenly become important for some reasons. If a law was passed tomorrow saying you could only have one child, but got an extra one for every inch over 6, just watch the penis length go up in the next few centuries.

This isn't an argument for or against recent change.

I'd say it is an argument that recent trends, if anything have been towards smaller penis size. There seems to be no status reasons now for a big penis. Maybe it helps with rape, but that is falling off in popularity, generally.

Recently, women have gained a lot of equality, and that will influence our genes in the future. More than likely, men will become more and more attractive, since women have more selective power than they did in the past and women are selecting based upon "sexiness" now since women have more economic power and can choose based upon other criteria.

well... yes and no. It is a plague of our time that no one has time for choosing sexual partners, they are all too busy working. The whole thing tends to be somewhat random and depend significantly upon who happens to be there at the right time. And I'd suggest this state of affairs has existed for some time. choosing by wealth has been replaced by pure random choice. Which might not be vastly different, since wealth is frequently a consequence of luck. It springs to mind that people look for different things in mates than in sex partners, and they will still not simply be choosing by looks, which anyway was still one consideration if choosing between equally wealthy suitors.

This is irrelevant to whether or not proto-humans used tools that needed strength as well as skill to make them useful.The original point was that the gender with the selective power has the practical body, like men have.

I dont see that men have the practical body. What is impractical about the female body? Strength wise i hear it is worse on peak strength but much better at endurance. The males are grunts to expend in a war.

Women have breasts before they bear young, which makes us totally unique and it's obviously a trait selected for by men.

Not for starting child bearing immediately at 11 to maximise reproductive years? A body which comes ready at the same time?

Women's bodies are small and sparsely muscled, which also seem to be features men select for. Men on the other hand are faster, taller, and stronger and built for practical physical tasks.

As I said, why do women need to be muscular? The men are competitively chosen for their ability as guards. Women dont need to waste body resources on unnecessary muscles.

Of course men like to think their cocks make them the peacocks, waving them around hoping that a woman will choose them to mate with.

You are saying that men believe they need to be peacocks. Maybe their genetics is in accord with their mindset,whichis why they have those showoff muscles and (arguable) showoff dicks.

The problem is that there's more evidence that women were sexually selected for and there's the lack of evidence that women choose men based on cock size.

But lots of evidence men are programmed to believe they are competing for women, which rightly or wrongly they may associate with cock size.

What do you mean 'evidence women were sexually selected for'? all animals are selected by sexual reproduction to fit their environment. If you mean, women are far better equipped to reproduce themselves than men are, damn true.

And what about LPSG? If women really selected based on cock size, making men the peacocks, then this board should be chock full of horny women competing for the attention the men here. All these hung guys should be swimming in more pussy than they can handle, because a lot of these guys are in the upper 5% for size. Unfortunately, there's a lot of threads where straight guys talk about their problems hooking up with women, and a lot of virgins here. LPSG can barely keep 100 women around. That doesn't support the assumption of men who believe in sexual selection by women for cock size.

Exactly! getting a woman is hard work! Damn sure they are competing. This place may be about cocks, but I m sure everyone here does not think just about this.

So why are men so obsessed with their penises, to the point that they assume women are, too? Well, maybe men are supposed to be, because maybe that was a lot more important once upon a time. I don't know if that's true, but having been a member of LPSG for a while now, I've asked myself that "why" question a lot.

Or perhaps more simply men are genetically programmed to compete for women, though they arent programmed exactly how to do this. Part of this is competing with each other, so even the straight guys are obsessive about who has the biggest this or that, because they all want to be top peacock showing off. Its all part of the uncertainty of being the sex which has to compete that you do not know exactly what might swing it for you.

 

[petite]

Look, I know this is a long thread, but I've gone over a lot of this stuff two or three times already. Some of it more than that. For example, I DID discuss the fear response AND I included a link to Meredith Chiver's resesarch on female arousal responses. I referred to that post later on instead describing it again because I already described it earlier in the thread.

Anyway, you're too skeptical for me. I think we're going to have to agree that we disagree with each other.

 

[kc2007]

Of course men like to think their cocks make them the peacocks, waving them around hoping that a woman will choose them to mate with. The problem is that there's more evidence that women were sexually selected for and there's the lack of evidence that women choose men based on cock size. There's no evidence that women prefer larger dildos or vibrators, as I mentioned earlier. That's easy to check out. Just go to any online sex shop where women leave lots of reviews. The highest rated ones are all"average" size. Big ones aren't popular and get lower ratings because of complaints about being too big. Not even on Fetlife do the large cock groups get a lot of female traffic, and those women are the kinkiest women on earth. Those groups are pathetically small, consisting of a few hundred members and dead, too, so not even the fetishy women are into big cocks.

And what about LPSG? If women really selected based on cock size, making men the peacocks, then this board should be chock full of horny women competing for the attention the men here. All these hung guys should be swimming in more pussy than they can handle, because a lot of these guys are in the upper 5% for size. Unfortunately, there's a lot of threads where straight guys talk about their problems hooking up with women, and a lot of virgins here. LPSG can barely keep 100 women around. That doesn't support the assumption of men who believe in sexual selection by women for cock size.

So why are men so obsessed with their penises, to the point that they assume women are, too? Well, maybe men are supposed to be, because maybe that was a lot more important once upon a time. I don't know if that's true, but having been a member of LPSG for a while now, I've asked myself that "why" question a lot.

I agree with most of this Petite. But I still think straight men like to show off their penises to women rather than other men to "compare". Granted, being on this site has been an education on the sizes and shapes of penises and mine comparatively to other ones, I'm still here to because women are here. I wouldn't be here otherwise. Even if you were the only the only real woman here :frown1: , that would be reason enough to show off my enormous manhood and fish for compliments. And I also think women had much more selective power who they chose to mate with throughout history, even if it had to be done much more secretly than it has in recent history. And at one point in time, penis size probably played into who early human women mated with. All you stated about how modern day women feel about the penis is absolutely true, but even women today admit a bigger, thicker penis looks more impressive. This is likely simply genetics and instinct, and before women became so liberated.

 

[RawDog]

I've read most of this thread, but not sure if this has been mentioned; Have there been any studies done on cervical mucus displacement? I'm no OB/GYB, but if the coronal ridge of the penis displaces "stuff", wouldn't it be more likely used in scraping off the mucus on the cervix that's designed to slow (and protect in the process) sperm?

 

[B_subgirrl]

I've read most of this thread, but not sure if this has been mentioned; Have there been any studies done on cervical mucus displacement? I'm no OB/GYB, but if the coronal ridge of the penis displaces "stuff", wouldn't it be more likely used in scraping off the mucus on the cervix that's designed to slow (and protect in the process) sperm?

Good point! I like it. I'm sure someone will come in to tell us why it isn't very likely though :tongue:.

 

[RawDog]

Good point! I like it. I'm sure someone will come in to tell us why it isn't very likely though :tongue:.

The thought dawned on me from your other post about head size, vaginal canal size and penis size.

Sometimes it pays to stalk you.

 

[B_subgirrl]

The thought dawned on me from your other post about head size, vaginal canal size and penis size.

Sometimes it pays to stalk you.

It always pays to stalk me, honey :wink::tongue:

 

[RawDog]

It always pays to stalk me, honey :wink::tongue:

It better pay... it's hard work stalking you when you're busy stalking me.

 

[B_subgirrl]

It better pay... it's hard work stalking you when you're busy stalking me.

ROFL :biggrin1:. Nah, when I'm stalking you it makes me EASIER to find. After all, just hang out where you last posted and you can guarantee I'll appear before long :biggrin1:.

 

[PerfectlySexy]

Wish I had seen this thread earlier. I've also read Sex at Dawn and it does provide hypotheses to answer a lot of questions raised in these postings. I want to take some time to respond, but this is a lot of info to process and respond to so my apologies for redundancy.

Why, under the same argument would Chimpanzee penises not be equally large? Or even larger, since they are more promiscuous?
But they're far smaller, roughly half the size of the human penis.

Interesting theory here, but I'm not sure it passes the sniff test.

The theory is Bonobos and Chimpanzees engage in sperm competition by delivering more sperm to outcompete each other. Those that produce more sperm are more successful in reproducing and thus pass on the genes for producing more sperm. Humans also produce more sperm than other primates (except chimpanzees and bonobos) but in addition, the theory goes, the penis size and shape is what enables them to outcompete each other. The glans does seem to have a suction affect in a woman's vagina. And to answer the critique of why a man does not pull his own sperm out of the vagina the theory is this is why the head of the penis goes soft immediately after orgasm to break the vacuum. I definitely feel this has been true for me, even if I stay relatively hard after orgasm, the head always shrinks and softens a bit.

Penis size will increase somewhat in the future because in this day and age women are free to choose their mate.

Actually, according to the theories in Sex At Dawn the opposite is true. Monogamous primates like Gibbons have extremely small penises. Since there is no sperm competition in a monogamous society each male has a greater chance of passing on his genes. Thus there is very little advantage to the biological mechanisms for sperm competition and so over time those should become less prevalent. Human penises should get smaller and human males should produce less sperm. They try to argue that we're seeing this already with how sharply male sperm rates are dropping but I tend to think this is much more likely due to environmental factors.

Also, I don't think it's useful to think of a "gangbang gene". What the authors of Sex At Dawn, among others, suggest is that humans are promiscuous and that women had sex with more partners more frequently throughout much of our history. And of course, this remains largely true today as both men and women continue to be promiscuous despite the social, legal, and religious sanctions against doing so. This is in fact one of the central arguments of the book: if humans were naturally monogamous than monogamy wouldn't be as rare as it clearly is our society. Also, if humans were naturally monogamous our mating patterns and biology should be more similar to gibbons than chimpanzees and bonobos: very small penises, just enough sperm to do the job (ie much less than humans currently produce), infrequent desire to mate and hence infrequent mating.

 

[PerfectlySexy]

Does that mean that all gorillas except for silverbacks abstain from sex for their entire lives?

While this may happen I would posit that the other gorillas get up to some hanky panky from time to time. However, it is the silverback who mates with all of the females and who then has the greatest reproductive success. The silverback dominates the other males by size and strength and thus a feedback loop is setup for size and strength which is why male gorillas are twice the size of females. Again, this is presented in Sex At Dawn.

I think it's pretty obvious that female sexual selection has played a part in the evolution of the human size. Back when humans wore less clothes and especially in warmer climates, women would probably select a mate based partly on penis size. Of course a woman is going to select a big penis with a fat pair of balls over a small penis to mate with. Even today women say regardless of how they feel, a larger penis is more attractive to look at and is considered more masculine. Of course as time went on and social norms developed and women started also being concerned with what feels good and people started covering themselves up more, this selection criteria is probably much less prevalent today. The average penis size is 6x5 and think the vagina is about this size as well when aroused. There has got to be more to this than coincidence.

The unstated assumption is that a woman was selecting 1 mate. Plenty of evidence from tribal societies who have histories far longer than civilization suggests that this is not how humans often organize themselves. Women may in fact have done very little "selecting" but rather sought out various mates and the selection was more a product of biology (ie sperm competition, though that term is somewhat a misnomer since it doesn't reflect the various factors that a woman's biology adds to the process).

Ah, I agree with your reasoning about why we find big penises to be attractive, but as an earlier poster pointed out, extracting semen from the vagina is useless as a reproductive strategy, since the best swimmers have already entered the uterus and fallopian tube by then and the sperm left in the vagina are the "losers" in the race.

This may not be accurate as 1) women have their own obstacle course for the sperm and 2) the design of the penis may well suck sperm from the uterus and fallopian tubes. Granted as noted earlier the experimental design for testing these are open to criticism but it can not be said that there is no evidence to support this. Certainly the vacuum sensation may be familiar to people on this site. It can be powerful enough to make some incredibly loud noises and fluid is sucked all over the vagina.

"
These are good points AFTER the Agricultural Revolution, which only happened 10,000 years ago. That's when human beings organized society in terms of possession and inheritance. This is also when the nuclear family concept was developed.
Before 10,000 years ago, most humans on earth organized in tribal communities, and many of those nations of people believed that babies were composites of the semen of many different men in the group. Which was beneficial to the women AND their offspring if many men in the tribe believed they had personal investment in the wellness and health of that child.
The most concise and readily available source for this information can be found in a book called "Sex at Dawn". It's a great resource for those of us not necessarily interested in reading incredibly dry, academic research on the topic. Enjoy!

Well said, and just wanted to point out that "Sex at Dawn" was how this topic got started in the first place. Even if these ideas seem ridiculous the book is a fun read and will give you a lot to think about. It is always difficult to infer behavior prior to civilization and so the research presented could be easily dismissed but this book provides a nice counter-balance to other theories presented by evolutionary psychologists which are more prevalent in the mainstream psyche (such as women "naturally" look for a good provider to protect her and raise her children).

 

[Gillette]

I haven't read the whole thread yet but these points begged to be addressed.

The way that selection works in evolution is always based on the feedback loop concept, so that the end result taken as far as possible as long as it provides an advantage, [or] until that particular feature is limited by some other evolutionary factor relating to survival or reproductive advantage.

This much is correct. However, I think placing too much importance on female selection is a mistake.

Female selection in regards to evolution is rarely a deliberate selection of a specific trait. Giraffes with longer necks experienced less competition for food and were thus better fed. When it comes to mating competition he's healthier and more likely to win challenges. He gets the girl. His progeny carry his genes and likely the trait, the trend continues. It's not a Sadie Hawkins dance.

Cows have a four chambered stomach as a result of evolution. This isn't because the females could tell and selected for it. The trait worked better than the other versions and the organisms with the development survived better than those who didn't.

It's worth remembering that plants have undergone heaps of evolution as well and yet we don't see female selection at work. Ever seen a flower spitting out undesirable pollen? "Eww, not his"

Similarly in humans, if females were encoded to desire gang-banging, considering how much freedom we now have, wouldn't modern women be getting gangbanged at a much more frequent rate?

No one suggested that women were encoded to desire gang banging. You yourself mentioned that women likely had little choice.

It could very likely just have been a social thing like certain chimp species.
"Woot! We defeated the other tribe!/Hunted enough meat for a year! ORGY!"

Maybe, as the vagina (and other female organs) grew larger to work with bipedalism and comparatively large-headed babies, the penis had to grow apace.

I do believe bipedalism had an indirect influence on human penis size in relation to other primates. Humans are the only primates whose locomotion is exclusively bipedal in adulthood. Standing upright immediately after sex allows for the loss of most of the deposited sperm due to gravity (something that would be less of an issue for chimps and apes bent forward walking on all fours).

Enter the orgasm. After sex, if it's just so so, I still have energy to burn. After I have mmm, mmm, good sex I haven't the desire to move and often drop off to sleep, whether I've had an orgasm or not. The internal massage is potent.

My speculation is that the larger penis (in this context larger being present day average size with small being one of a similar body/cock ratio to the apes) delivered more sensation during copulation if not an actual orgasm which triggered a relaxed, "I'm just going to lay here awhile and savour the moment", state in the female, which in turn gave all the semen deposited more time and a better chance to travel from vagina to uterus and onward before she stood and gravity did it's thing.

Could women have selected deliberately for that lovely feeling? Possibly, but my bet is they didn't make the concious link as the development in size was likely a gradual thing. It just happened to work and as a result the trait was passed on.

Also consider reproductive success if the women were monogamous.

-A man with a shorter penis deposits his sperm. It has to swim further in an environment which is chemically hostile (from the native microflora producing lactic acid) to sperm to reach the cervix. Reduced chance of fertilization.
-A man with a longer penis deposits his sperm closer. Less swimming. Increased chance of fertilization.

I've read somewhere that some sperms have the function of hunter-killers, killing other mens' sperms in the vagina, and assuming a woman has had several recent lovers, the man with the most aggressive sperm fertilizes her. Penis size wouldn't be relevant here.

Yes and no. You're right about the most aggressive swimmers fertilizing the egg but that only happens if those sperm remain in the vagina.

Back to the gang bang and the coronal "scoop".

On the out-stroke the ridge serves to scrape previously deposited sperm out of the vaginal canal, NOT just to prevent a man's hand from sliding off and hitting him in the forehead during masturbation.

Ah, but he'd be pushing it deeper on the in-stroke. This is where size comes into play.

Simple displacement experiment for anyone who has a hair treatment glove about. Fill it with water then stick your pinky finger in. How much water comes out? Now stick your whole hand in the glove. How much water comes out?

Longer and thicker displaces more semen forcing it around and behind the head where the scoop then drags it back out of the vagina.

Studies of animal evolution have revealed that the gender that posses the selective power is always the "plain" one with the more practical traits for survival and the gender that is sexually selected is the one with the extreme traits, which are frequently impractical for survival. This is the observation that Darwin made. The male peacock is hindered by brightly colored tailfeathers which make flight impossible, evasion on the ground difficult, and make him much more visible to predators. The female is plainer and without the large tailfeathers and is more likely to evade predators as a result, her body is much more practical for survival.

Wow.

Female peacocks are attracted to males with the largest display plumage because having something that is so disadvantageous to survival and yet surviving despite the greater disadvantage than his competitors signals to the female that this male is faster/stronger/smarter than ones with a smaller display.

So let's compare the male and female of our species. Which do you consider to be the physically practical gender in humans? The male is large and strong, his torso doesn't posses the nipped in waist that weakens it. He possesses greater height and speed. The female posses enlarged mammary glans once she becomes of a fertile age, which are uncommon among mammals that are not nursing. Looking at the physical characteristics of human males and females, I think it's clear that the females weren't the ones with the selective power in our evolutionary past, hence their attractive but impractical bodies now.

Double wow.
That must explain why all male humans have the same colour eyes, hair and skin. Oh, wait...

Women have wider hips than our primate counterparts because walking upright required a better cradle for carrying babies in utero. Our breasts are larger because standing upright diminished the prominence of the buttocks as a sexual signal.

Instead of comparing us to birds and plumage look to other mammals and more specifically primates. With the arrival of sexual maturity the males engage in competitive play fighting where the females don't. This play fighting is used when it's time to mate and the males have to fight each other to prove their superiority to the female. I've never seen a case in primates where the females fought each other for the mating rights of a male.

Also, it is interesting to note that even though the Bonobo chimp has sex for pleasure, their penises are not larger than the penises of chimpanzees, which suggests an alternative reason for why human penises are so large.

Bipedal locomotion.

 

[B_subgirrl]

I do believe bipedalism had an indirect influence on human penis size in relation to other primates. Humans are the only primates whose locomotion is exclusively bipedal in adulthood. Standing upright immediately after sex allows for the loss of most of the deposited sperm due to gravity (something that would be less of an issue for chimps and apes bent forward walking on all fours).

Enter the orgasm. After sex, if it's just so so, I still have energy to burn. After I have mmm, mmm, good sex I haven't the desire to move and often drop off to sleep, whether I've had an orgasm or not. The internal massage is potent.

My speculation is that the larger penis (in this context larger being present day average size with small being one of a similar body/cock ratio to the apes) delivered more sensation during copulation if not an actual orgasm which triggered a relaxed, "I'm just going to lay here awhile and savour the moment", state in the female, which in turn gave all the semen deposited more time and a better chance to travel from vagina to uterus and onward before she stood and gravity did it's thing.

Could women have selected deliberately for that lovely feeling? Possibly, but my bet is they didn't make the concious link as the development in size was likely a gradual thing. It just happened to work and as a result the trait was passed on.

Also consider reproductive success if the women were monogamous.

-A man with a shorter penis deposits his sperm. It has to swim further in an environment which is chemically hostile (from the native microflora producing lactic acid) to sperm to reach the cervix. Reduced chance of fertilization.
-A man with a longer penis deposits his sperm closer. Less swimming. Increased chance of fertilization.

I'm liking this theory. The second part was more where my thoughts were headed, but the first part fits well with it.

 

[PerfectlySexy]

Sex At Dawn theorizes that men are turned on by signals of sperm competition. They use the sight of other men's sperm as an example (presence of cumshots in porn, multiple male cumshots on women, bukkake, popularity of large cumshots in porn). I'm curious as to whether this goes for the size of the glans as well (bigger glans means more suction, more semen displacement, more sperm competition). So I've created a poll here:

http://www.lpsg.org/223294-large-aka-mushroom-head-as.html

 

[sex_pirate]

Interesting thoughts from "The Mating Mind" by Geoffrey Miller....

If sperm competition were the driving force behind penis evolution, males might have evolved scary-looking flagellated genitals. Men would copulate by inserting their equipment, instantly flooding the cervix with half a pint of semen, and then lying on top of the woman for the next three days to make sure no rivals have the chance to introduce competing sperm. I understand that such behavior is quite rare.

Against the visual display idea, however, is the fact that human penises are a rather sorry spectacle. We have not evolved a bright purplish-pink scrotum and a bright red penis with a yellow tip, as one species of mandrill has. Male vervet monkeys have a blue scrotum and a red penis set off against white hair. When primate penises are selected for visual appearance, they evolve much more color, and females seem to consider them much more attractive. The male human penis does not appear to be especially well adapted for producing auditory, olfactory, or gustatory stimulation. That leaves the sense of touch as the medium for female choice.

 

[PerfectlySexy]

If sperm competition were the driving force behind penis evolution, males might have evolved scary-looking flagellated genitals.

Operative term is "might have". There are any numbers of way sperm competition can happen. Supposedly there is an insect where the male injects his sperm into another male so when the injected male copulates he's spreading another male's sperm. But saying "if sperm competition were the driving force behind penis evolution human males might have developed the ability to inject their sperm into the testicles of other men" sounds silly. Sure, they "might have", but they didn't. Like chimps and bonobos, humans developed a capacity for producing more semen, but unlike chimps and bonobos, humans have the glans which some evidence suggests sucks out competing semen. Humans take longer to ejaculate than chimps and bonobos who do much more of the flooding trick. Humans taking longer gives more time for the suction effect to work, and perhaps has other advantages as well.

 

[3151]

The theory of "further to swim" may be discounted by the volume of sperm that is ejaculated during intercourse.... somewhere between 250-300 million sperm are released each time the guy cums, so...

What is better, an "above average" guy with a 4 inch penis who shoots 350 million sperm, or a "below average" guy with an 8 inch penis who only shoots 200 million?

As far as size selection... up until recently (and in many cultures still), many women don't see their husband naked unti after marriage (or just before).

This goes back to the sex stories where the woman leaves her 4 inch husband and three kids for a guy with 11 inches.... maybe good fantasy, but hardly realistic.

In early human times, don't you think a woman wanted a man who could build shelter, hunt, gather and protect her more than a guy with a big shlong?

There is little relation between height, mass and penis size... so the 6'4 muscled guy who could protect and hunt may not be hung at all.

In more modern times, the man still had to hunt, and more recently earn a living for a family. Again... a "career man" who makes $100K or a HS drop out who makes $20K but has a big unit?

It would be interesting to see if the Trumps, Rockefellers, Kennedys, and others have bigger cocks than those who carry lunch buckets to work.