Why absence of human penis bone?

I found little information about penis bone on internet. The baculum (also penis bone, penile bone or os penis) is a bone found in the penis of most placental mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee. The bone aids sexual intercourse by maintaining sufficient stiffness during sexual penetration. The female equivalent is the os clitoridis – a bone in the clitoris. Mammals having a penile bone (in males) and a clitoral bone (in females) include various eutherians. Key words: female mammals also have a bone in clitoral shaft.

Unlike other primates, humans lack an os penis or os clitoris; however, this bone is much reduced among the great apes: in many ape species it is a relatively insignificant 10–20 mm structure. Such a wide distribution among placental mammals suggests that the bone evolved early in the history of these mammals, and was subsequently lost in certain groups. There are two main theories about absence of human penis bone. 

One theory is, it has long been believed, that humans evolved smooth penises as a result of adopting a more monogamous reproductive strategy than their early human ancestors. Those ancestors may have used penile spines to remove the sperm of competitors when they mated with females. However, exactly how this change came about is not known.

I don’t agree with this view at all. The reason is very simple: Monogamy is definitely a product of modern civilization, but the absence of penis bone maybe happened in millions of years ago, I really do not believe that our human ancestors, at the beginning, are monogamous. Here I emphasize my view about monogamy again that the reason of emergence of monogamy is not because of human rights or love, and it is totally a result of interests’ compromise between males. Love is just a emotion between two equal and independent person, no materials money or survival dependencies. Woman starting went out of the kitchen and began to make money is because of the First World War, so I think love is absolutely a modern vocabulary. Women, as a vulnerable group, choose a marriage only for survival before really economic independence. Even if love really exists long time ago, it must be a luxury, belonged to the wealthy aristocracy. Until now, in some areas, women still a male appendage, and they can’t choose their marriage, they can’t go to school like boys, they can’t even take off the fucking veil. What is love? Bullshit. In old China, the girls can’t even meet the husbands before the night they get married. Now, the more highly education women got, the more they choose to be celibacy. It is definitely a progress of women self-awareness that they start the pursuit of the spiritual world, after the satisfaction of the material world, not only reproduction, but it is just a good start, still far from completely self-consciousness.

The other theory is that the loss of the bone in humans, when it is present in our nearest related species the chimpanzee, is because humans "evolved a mating system in which the male tended to accompany a particular female all the time to try to ensure paternity of her children" which allows for frequent matings of short duration. Observation suggests that primates with a baculum only infrequently encounter females, but engage in longer periods of copulation that the baculum makes possible, thereby maximizing their chances of fathering the female's offspring. Human females exhibit concealed ovulation also known as 'hidden estrus', meaning it is almost impossible to tell when the female is fertile, so frequent matings would be necessary to ensure paternity.

I don’t fully agree with this explanation. First I admit the truth of concealed ovulation in female human, maybe that triggered frequent matings would be necessary to ensure female to be pregnant, but there is no relationship between frequent matings and the absence of human penis bone. Conversely, I do believe that the existence of penis bone is helpful for mating. Because the penis has a very simple job to do: to maintain sufficient stiffness to enter an orifice during the mating, and to deliver sperm. The baculum is generally kept in the male's abdomen until it is required, at which point abdominal muscles push it out into the penis, thus causing an erection. The function of penis bone is to help males maintain an erection long enough to penetrate a female's reproductive tract and deliver sperm. You can imagine that, when a female in ovulation period, but the male is not the mood to mate and can’t get his penis hard, and the result is he can’t even complete the insertion. What if he still has penis bone? He can insert anyway, so I think the presence of the penis bone is very conducive to mating. I do believe there is no word “Impotence”, if the penis bone still on human.

So, inevitably, this brings us to the question of why humans are the only apes to lack a penis bone. I don’t agree with the two explanations of absence of penis bone, and we have to find the answers in some different views. 

1, From the view of mating season and mating purposes
Undoubtedly, all the animals have specific mating season, except human. Here mating season means the seasonal period when a female animal's estrous cycle is active, signaling animals to mate. Only during the female estrus, they exhibit a sexually receptive behavior, a situation that may be signaled by visible physiologic changes. A signal trait of estrus is the lordosis reflex, in which the animal spontaneously elevates her hindquarters. What about our human? Key words: Only during the female estrus, they exhibit a sexually receptive behavior. Apparently, our human can mate at any time all around the year. Why other animals only mate in female estrous period, except our human?

The authoritative view is given for that: the mating season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding, and humans have evolved not to need one and many animals do have a mating season because their food resources or the temperature where they live changes throughout the year, so the there's no real need for a mating season for humans. I think this explanation is very classical, but I want to dig some deeper factors: the mating purposes. 

I do believe that the mating purpose during mostly non-human animals is for reproduction, but what about our human? What is the purpose of human mating? Why do male human need to mate also during female non-ovulation period? Why do women still have to be “receptacle”, even after her menopause? Why female human have to accept the sexual behavior during non-ovulation period? I really do have many questions, but I think my questions are not hard to explain. Come on, poor women; please do not forget what Freud said “the vagina has value only as a receptacle for penis.”

Besides this classical theory, I have my story to say. Purpose determines the action; conversely, different actions are due to different purposes. Apparently, mating purpose during animals is only for reproduction, so they choose the strategy that only mating in most suitable season and female ovulation period. During human race, sex is so much more than a means of reproduction. What is our purpose of mating? Fun, pleasure and relax. Here I want to emphasize that the fun, pleasure and relax I mean is for self, not for others. I agree with the Adam Smith’s statement about the relationship between Egoism and Altruism. He writes in his Wealth of Nations: “It is not from the benevolence of the butcher, the brewer, or the baker, that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages.” Here I use the same logic to say, in the game of sex, every orgasm is a result of masturbation, no one can give you an orgasm, but yourself, and every one only have the ability for self-masturbation, but no other-masturbation.

Here I want to ask the followers of G-spot some questions: do you believe female mammals also have G-spot? Because all female mammals share the same reproductive system, ovary, uterus and vagina so on, according to G-spot theory, non-human female mammals also deserve to get orgasm from male penetration. Maybe you should believe that female animals were fucked to get multiple orgasms, because they always have crazy mating so many times during mating season. Next question: why they exhibit a sexually receptive behavior only during female estrus? Why do they refuse to experience the amazing multiple orgasms in non-estrus period? Maybe they are stupid, yeah?

2, From the different ways of sex

Traditional intercourse:
At the time of penetration, the canine penis is not erect, and only able to penetrate the female because it includes a narrow bone called the "baculum ", a feature of most placental mammals. The baculum is kept in the abdomen and, when needed, a set of muscles push it into a sheath in the fleshy part of the penis. It enters within the erectile tissue, providing rigidness to aid during the copulation. Unlike human sexual intercourse , where the male penis commonly becomes erect before entering the female, canine copulation involves the male first penetrating the female, after which swelling of the penis to erection occurs, which usually happens rapidly.
Briefly speaking, because of absence of penis bone, male human need to get penis hard first, then penetrate into woman’s body; for other male mammals with baculum, they penetrate into female body using penis bone first, and then penis get erection because of rub. I do believe that whether penis gets erect or not before insert is the key in human sex evolution. What does this mean? What exactly makes penis of male human get hard before any touch of it. Let me give you further details.

Masturbation is the sexual stimulation of one's own genitals, usually to the point of orgasm. The stimulation can be performed using the hands, fingers, everyday objects, or dedicated sex toys. Key words: usually to the point of orgasm. In childhood the male and female bodies are very similar, both without masturbation. Masturbation is quite common among young adolescent males, since the development of male secondary sexual characteristics, but few women can get real orgasm through masturbation after female secondary sexual characteristics. I do think that is the key why female suffer sexual dysfunction, because men do have a good start in this subject, but women lag behind at the beginning. Why is that? 

Animal masturbation has been observed in many species, according to some news, but I am not going to believe them all. Some news said birds can masturbate, that is not possible at all, because birds don’t even have penis, and they reproduce by cloaca kiss. I do believe masturbation is not so popular in the animal kingdom. If animals really have self-pleasuring behavior, as the stronger side, male must choose the strategy of rape to increase the enjoyment, whatever in female estrus period or not, but mostly of male animals still choose to mate only during female ovulation period. Please don’t tell me they respect female rights, so they choose masturbation, not rape. I am kidding. Let’s go back to the key words of masturbation: usually to the point of orgasm. I think we should differentiate so-called animals’ masturbation from human masturbation on this point. If the purpose of masturbation during animals is for ejaculation as same as male human, we can say that male animals really have masturbation; if the purpose is not for ejaculation, I do agree with this view that masturbation during animals may help to keep the genitals clean and stave off sexually-transmitted infections. We have lot of things unknown.

Homosexual behavior in animals:
Research indicates that various forms of same-sex sexual behavior are found throughout the animal kingdom. Homosexual behaviour has been observed in 1,500 animal species. The most well-known homosexual animal is the dwarf chimpanzee, one of humanity's closes relatives, and the entire species is bisexual. Homosexuality is also quite common among dolphins and killer whales and the pairing of males and females is fleeting, while between males, a pair can stay together for years. Homosexual behavior in animals is often performed in non-reproductive ways, using snout, flippers and genital rubbing, without regard to gender.

The following picture is two female domestic dogs engaging in sex play. 

What are they doing? Apparently, she can’t penetrate her clitoris into the other’s vagina. I guess she just rub her clitoris shaft against the other’s body for pleasure. Does she really enjoy the climax shiver like males? I really don’t know. If female mammals really can get the climax shiver through rubbing the clitoris shaft, female human was totally a joke.

Why homosexual behavior in animals is so common, even in birds, as you know, birds don’t even have penis at all, they can’t have the climax shiver through anyway. Birds that mate using this method touch their cloacae together, in some species for only a few seconds, sufficient time for sperm to be transferred from the male to the female. Why homosexual behavior happened if we think sex in animals is only for reproduction? For pleasure, fun or showing intimacy or ensuring loyalty or connection or strengthening the bonds for the group.

Let’s go back to the question that what exactly makes penis of male human get hard before any touch of it. Everyone knows that men always like to see porn, whenever in masturbation or in making love with someone. Why is that? I think because seeing porn can evoke men’s lust and penis can get erect as a physiological response. Obviously, men can not only rely on direct penis stimulation to get an erection, but also on the brain's sexual fantasies to get hard. It is undeniable sexual fantasies take very important role in human sex. Sometimes a man was hit by a bad thing, and he can’t get penis hard, whatever how hard you touch him. 

But in animals, the porn doesn’t work any more. For example, in a zoo, in order to breed more offspring during rare species, the staff played porn film in front of the animals, but unfortunately, non-human male mammals don’t become a sex machine after seeing porn like men. Compared to our human erotic intercourse, animals’ mating is very pure. 

Same action, but with different motives. It is not hard to understand, and I can give you another same logical example here: nipple sucking. I think you don’t feel any lust, when you saw a baby sucking a woman’s nipple, because the fact is the baby really doesn’t have any lust in the brain when sucking. What about a man? You have a very different feeling, when you see a man suck woman’s nipple, right? Because it is full of porn. Intercourse shares the same logic. What exactly makes so different between male human and male non-human mammals in sex? I think the key problem is the brain. In human, the reflex arc of sex includes the brain, but in the non-human animals, the reflex arc of sex only includes low central nervous spinal cord. That is why male can get erection when seeing porn, but other animals can’t. 

Wet dream:

A nocturnal emission or wet dream is a type of spontaneous orgasm, involving either erection 
and/or ejaculation during sleep for a male, or lubrication of the vagina for a female. Nocturnal 
emissions are most common during adolescence and early young adult years, but they may 
happen any time after puberty. It is possible to wake up during a wet dream, or to simply sleep
through it. There are numerous cultural and religious views on nocturnal emissions, such as 
caused by a succubus copulating so on and so forth. 

In short, I think the wet dream is due to the subconscious desire for sex. This subconscious must come from the brain, and I guess non-human mammals don’t have nocturnal emission, maybe animals don’t even have dream.

3, Main product and by-product: vasectomy
Vasectomy prevents sperm from mixing with semen by blocking the sperm ducts. After vasectomy, sperm continue to be produced. However, during ejaculation, the sperm make it only as far as the newly blocked point in the ducts, where they are reabsorbed. As a result, there are no sperm in the ejaculated semen during intercourse.

At the beginning, a lot of men are concerned about what changes in their sex life after the procedure. The short answer is that there is no adverse change in the quality of sexual enjoyment for either partner after a vasectomy. In fact, many people report improvements in sexual enjoyment because they no longer need to worry about an unwanted pregnancy. Orgasm, the pleasure we receive during climax is a physiological process that occurs in the brain is unaffected by the vasectomy nor is it related to the presence of sperm in the ejaculate. Sperm in the ejaculate has no relationship to the quality of your sexual intercourse or the satisfaction during intercourse you or your partner would have after a vasectomy. The only purpose of sperm in the ejaculate is to procreate. 
The key words: orgasm is a physiological process that occurs in the brain. Apparently, we can conclude that the orgasm, in human experience, is a bottom-up process, and in this process of nerve conduction, the main product is the pleasure in brain, and the by-product is discharge of sperm.

4, Refractory period:
As we all know, the male human has a refractory period after orgasm. What is refractory period exactly? Wikipedia gives the definition like that: in human sexuality, the refractory period is usually the recovery phase after orgasm during which it is physiologically impossible for a man to have additional orgasms. It varies widely among individuals, ranging from minutes to days. According to some researches, the post-orgasmic refractory period also occurs in other male animals. About the mechanism of refractory period, basically, the release of some special hormone, like prolactin and hormone oxytocin, are thought to be largely responsible for the post-orgasmic refractory period seen in men, and the amount by which oxytocin is increased may affect the length of each refractory period, and prolactin is considered to represses dopamine, which is responsible for sexual arousal. 

Frankly speaking, I don’t know the function of prolactin, oxytocin or dopamine exactly, but I noticed that refractory period must relate to some release of pituitary gland or brain. Though it is generally reported that women do not experience a refractory period and thus can experience an additional orgasm, or multiple orgasms, soon after the first, some sources state that both men and women experience a refractory period because women may also experience a period after orgasm in which further sexual stimulation does not produce excitement. Here I don’t want to tell you how stupid the idea of female multiple orgasms, and multiple orgasms mean no orgasm at all, but I want to go to another subject: do other non-human male mammals also have the post-orgasmic refractory period? 

Refractory period in male animals are very vague, including our closest relatives chimpanzees. Here I think lion’ mating is a classical example. Lions like most animals only mate during mating season. During a mating bout, a couple may copulate twenty to forty times a day for several days. Some lions mate over 50 times a day, but mostly of mating only last 10 seconds or less. Once the female has cubs, she will not mate again. Zoologists have not found significant refractory period in lions. I think it is not hard to understand, because refractory period must inevitably lead to drowsiness, if male lions have refractory period like men, they can’t accomplish the tough task like 50 times a day. In general, I don’t believe non-human mammals have refractory period after ejaculation, notice I use the word “ejaculation” here, not “orgasm”, because the refractory period is the result of the brain triggered, it come after orgasm, not ejaculation. Maybe that is why some males claim that sometimes they can ejaculate, but no orgasm. I think whether ejaculation or shiver is controlled by spine, but whether orgasm pleasure is controlled by brain. I will try to describe the details in future.
5, Key words: female mammals also have a bone in clitoral shaft.
I am curious that we can understand the meaning of existence of penis bone, if we consider the purpose to help the male to insert, why female mammals still have clitoris bone? Apparently, it has nothing to do. This question is as same as the function of clitoris shaft, it is useless, but female still have it. I think it is related to the genes on X chromosome. So far, most of mammals don’t lose the bone’s genes yet, but our human have lost it already.
Continue to ask, what is the premise of losing the genes? Of course it is not to affect animals’ survival and reproduction. In other words, those animals, who can get penis hard before insert, give the opportunity for the genes’ missing.
All in all, I do believe the evolution of the brain and nerves is the key to distinguish human from animals. We have to figure out something like orgasm is orgasm, ejaculation is ejaculation, and orgasm pleasure comes from higher central nervous system: Brain, and ejaculation reflex is controlled by lower central nervous system: Spine. We really have to redefine lots of things. I believe the evolution of human sex reflex arc from spine to brain is due to the rapid expansion of brain and nerves during X chromosome or autosomes, Y chromosome has nothing to do that. Ironically, after neural pathway established, Y used it much better than X. There are lots of things unknown, our human beings are still ignorant in many areas.