Human Biology

Why Our Physical Bodies Are As They Are

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WHY DID NEANDERTHALS GO EXTINCT? The perennial problem of what caused the extinction of Neanderthals is really quite simple. Homo sapiens coming in from Africa simply greatly outnumbered them. Thus the natural mixing automatically produces a merging of the two species into our single modern species which is still 2%-3% Neanderthal among people of European descent. For example if there were only 50 times as many H. sapiens as Neanderthals an even mixing of genes would produce the observed 2% range of Neanderthal DNA in modern humans.

So Neanderthals didn't really go extinct, they just merged into Homo sapiens slightly modifying us. No other mechanism than interbreeding between two species of greatly different populations is required. There is no requirement of better technology, extermination through conflict, or introduced epidemic required. There is no mystery here...

WHY DID HUMANS LOSE THEIR BODY HAIR? There are several theories I'd like to comment on here. The Aquatic Ape Theory (AAT) that humans lost their body hair during a time they were primarily aquatic. The Parasite Load Theory, that body hair was lost as a mechanism to make it easier to remove parasites. The Sexual Selection hypothesis, that individuals with less body hair were preferentially selected as mates. The Coincident Hypothesis, that body hair genes are associated with genes for other characteristics that were negatively selected. The Fire, Clothing, and Shelter hypothesis which posits that humans lost body hair as a result of the adoption of these technologies to keep them warm instead. The Brain Heat Dissipation Hypothesis, that larger brained early humans needed to lose more body heat to keep their larger brains from overheating. The Sweating Hypothesis, which points out that humans are one of the few animals that sweats from the whole body and sweating doesn't work if the body is covered with hair. There might of course be some combination of selective factors. A lot depends on when humans actually lost their body hair and there is little evidence of that. There is some indication in cave paintings of lines on human figures that might indicate hairiness but the evidence there is slight. And we must remember that human females are actually much more hairy than they appear due to the removal of armpit, leg and often pubic hair. In any case loss of body hair is just one of a number of strikingly unique characteristics of human physiognomy that are largely unexplained.

THE PARASITE LOAD THEORY: The parasite theory could not just depend on the general ectoparasite load common among mammals since all mammals are plagued by parasites. It would require a response to some very specific long term chronic parasite borne disease severe enough to select for less body hair. This could be due both to ease of removal of parasites which carried the disease, it is certainly a lot easier to find and remove ticks or fleas from a human than a dog, or might be due to the preference of that parasite for hair covered skin. Somewhat iffy but certainly a possible factor. There might well have been an associated sexual selection preference for individuals with less hair being likely to carry a lesser parasite load.

THE AQUATIC APE THEORY: This just seems a little too contrived and dependent on coincidence to me. And not bourne out by either evidence or reasonable assumptions. It assumes an awful lot of time in the water I think. Humans do seem to take to water more than most primates, though there are semi-aquatic rhesus and probiscus monkeys that inhabit swampy forests, and some actually swim around underwater collecting food. But note that none of these primates shows any consequent loss of fur due to their frequent time in the water. The point is that all aquatic adapted mammals that show loss of body hair (with the exception of elephants) are highly aquatic adapted in body form as well, something the human shows not the slightest trace of. Additionally we have the other hairless mammals such as Aardvarks and mole rats which spend no time in water at all, so obviously there is a non-aquatic mechanism at play there.

Widespread waterside as opposed to in water evolution I have no doubt of, at least among shore dwellers. But waterside life could not possibly select for hairlessness. Only prolonged life in the water itself could do that. And that I think is very unlikely. You are asking us to imagine some group of humans living nearly constantly in the water like hippos. If that had been true we would also have eyes and nostrils on top of our heads!

This also addresses the point about the linear human bodily form. This is the result of a fully upright posture based largely on structural changes in the hip bones and others. This comes from walking upright with free hands. Note the position of the head at 90^ angle to the upright spine which is maximally functional for standing and walking upright. If we were aquatic the head would not be held in this position as it positions the face and breathing apparatus underwater! Aquatic mammals have their heads positioned straight forward from the spine with the eyes and nostrils (or blowholes) toward the tops of the head to facilitate breathing.

Adipose layers again are no argument. Most of human obesity comes from the unlimited availability of rich foods made possible by the rise of agriculture. Also many other species that are not aquatic put on considerable seasonal fat layers. One can make nearly any mammal fat on a diet of too much rich food and no exercise. Just look at all those fat dogs. Certainly this canine obesity does not derive from aquatic precursors!

Some aquatic animals do sweat, although some proponents of the AAT seem to exaggerate the amount of sweating that animals like seals do. Also, remember that the model for "aquatic" we should be thinking of is not "dolphins and whales" but more like those Japanese monkeys that learned to wash dirt off sweet potatoes by taking them out into the sea. Only more so.

THE FIRE, CLOTHING AND SHELTER HYPOTHESIS: This theory depends a lot on when body hair was lost. The basic idea here is that body hair was lost because it wasn't needed to keep humans warm once they adopted fire, clothing and shelter. But we see no such loss of hair among mammals that live in the warmest of climates as we would expect if this were true. So fire and shelter I think are unlikely selectors. Clothing on the other hand could have been as hair is a buffer against the immediate environment and clothing subsumes that function and also may directly have had some inhibiting factor on body hair growth due to constant rubbing. We see this often among men who lose ankle hair due to wearing socks.

THE SWEAT GLAND CONNECTION: There certainly seems to be a connection with loss of body hair and the proliferation of sweat glands, something that few other mammals have in such abundance. Sweating doesn't work that well to cool the body when it is covered with fur. However most mammals do sweat. Some, like giraffes (and I assume other antelopes), use apocrine sweat glands. Human beings, and others like gorillas, chimps and horses, use eccrine sweat glands to cool themselves. The absence or presence of at least light fur doesn't seem to make that much difference: horses are covered in hair, and they sweat like champions. And it is uncertain whether the proliferation of sweat glands developed before, after or with the loss of body hair.

THE BRAIN HEAT DISPERSAL THEORY: This theory is that as humans developed larger brains and upright posture walking around on open savanna they had to lose more body heat to keep their brains from overheating. One might wonder why then was head hair not lost instead but presumably that insulated the head from direct sunlight. I'm not convinced that humans needed more cooling capacity because their larger brain and upright posture was more prone to overheating.

THE ASSOCIATED GENE HYPOTHESIS: It is certainly true that selecting for one gene can have many associated consequences as shown by the Soviet experiments with breeding fur foxes for docility which unexpectedly produced dog-like floppy ears and spotted coats as well. One could speculate that environmental selection for something else could also result in human body hair loss if the same gene(s) controlled for both attributes. We would need some evidence from molecular biology for that. What would those characteristics likely be? I think that's an unanswered question at this point.

THE SEXUAL SELECTION THEORY: It does seem that modern humans in general have a sexual preference for partners with less body hair.We see this is the widespread removal of armpit, leg and often pubic hair among modern women, and the ancients also did this as well in many cases. We might postulate this preference had a strong selective capacity in view of the rather unique importance of visual appeal in mate selection among humans, as opposed to the more strongly olfactory scent of female estrus among most mammals. I think we can make quite a strong case for this one. I don't think the preference for a female not covered with body hair is purely a matter of familiarity. I think this is fairly strong evidence of an innate human preference for less body hair and as such is strong evidence for the sexual selection theory.

Asking the question 'why don't other mammals have sexual preference for partners with less body hair?' gets us nowhere. In one sense it's as meaningless as asking why is a lion a carnivore and an a zebra a herbivore. That just happens to be the way those species evolved. However quite a good case can be made for the preference for less body hair arising out of an increasing capacity to experience beauty. The ability to experience beauty arises with an increased capacity for abstract thought which allows the appreciation of such things as symmetry, texture, color and natural form as abstract things in themselves. In other words, the preference for less body hair arose with the ability of humans to experience the beautiful. This is evidenced by our obvious appreciation of the beauty of symmetry and form, skin coloration and texture of the bodies and skins of the opposite sex.

Another important factor is that less body hair (in combination with the exceptionally thin and sensitive skin that humans have) enables a much greater tactile caressing eroticism than would be possible with heavy body hair. While touch and grooming and cuddling (mothers and young especially) is common among many mammals, no other mammal has the pervasive sexual caressing, kissing and fondling that humans enjoy so much. This highly pleasurable and sexually selective behavior is only made possible by lack of heavy body hair. It is pointed out that human infants and children have less body hair than adults. I don't think this is a problem for my thesis as the young of many mammals also have considerably less body hair than the adults. This is more a factor of body hair having no function in utero. There is an interesting consequence here however, and that is if humans find less body hair sexually attractive this could be a factor in the apparent widespread human tendency toward pedophilia. This in fact actually lends some additional weight to my argument for sexual selection being the determinant in body hair loss.

Perhaps instead one could argue that relative neotenous hairlessness stimulates maternal-like or paternal-like caring responses in mates and thus tends to strengthen and prolong pair bonds so as to facilitate the long term bonding necessary for rearing human young. That seems a reasonable possibility. Think of the very heavy use of the word 'baby' to apply to mates and lovers as strong additional evidence for my suggestion.

To sum up, the sexual selection theory seems to me by far the most likely theory to explain the loss of human body hair.

WHY DO HUMAN FEMALES ORNAMENT THEMSELVES WHEN IN NATURE IT IS USUALLY MALES THAT ARE ORNAMENTED? Male sexual ornamentation is most striking among birds. But in mammals as well it is usually the male that is sexually ornamented with say manes or antlers. The man's beard is the analogue to the lion's mane. Apart from antlers though the degree of ornamentation is certainly minor compared to birds. In mammals, we more often see male dominance battles for control of females rather than overt sexual ornamentation.

The big question is why human females ornament themselves so excessively with clothing, jewelry and makeup when female ornamentation is almost never seen in nature. The sexual ornamentation of women exhibited in clothing, makeup etc. is not genetic ornamentation, and seems to actually be contrary to a woman's natural lack of ornamentation. As such it requires a separate explanation. On the other hand with no or minimal scent of estrus (so called hidden estrus) to signal sexual receptiveness to the male women have evolved prominent breasts and buttocks which signal the human female's near constant receptiveness. No doubt it has something to do with the strong societal regulation of overt male competition over females. Human males do not routinely engage in violent combat to win females which is fortunate given the near constant receptiveness of women! In such a male dominance vacuum, the female tends to develop more sexual power and clothes and makeup are how women now compete for men. As I've noted before, the effect of civilization is to heavily domesticate the male, to some degree a necessity to ensure social order and stability. The anomalous phenomenon of artificial human female sexual ornamentation may be the result. When men can't fight over females, females must take the initiative to signal their interest to the male of their choice.

Thus in humans we have the somewhat anomalous situation where females actually do most of the sexual signaling and choosing of mates.

MALE AND FEMALE ORGASMS: The feminist notion that men can't intelligently comment on the female orgasm just doesn't stand up to scrutiny. Presumably feminists are speaking from their personal experience or lack of it but consider the sample size. Assuming they are heterosexual then at best they have experienced only one woman's female orgasms, whereas as a man I've experienced those of a couple hundred different women and most heterosexual males will have experienced far more female orgasms than most heterosexual women. In that sense men know things about the female orgasm that women are unlikely to. So obviously men know much more about female orgasms in general than women do, a basic fact of scientific methodology feminists seems to ignore.

How can anyone say with a straight face that 'women know more about the female orgasm than men'? Since when did personal experience substitute for and trump scientific knowledge? Who knows more about clams, clams themselves or the scientists that study them? Even if personal experience were the prime determining factor your logic still wouldn't hold. A man will have intimately experienced the numerous female orgasms of his partners in many different variations. A heterosexual woman will have ever experienced at best only her own female orgasms, not the large sample a man will be intimately familiar with. It is quite obvious that any man worth his salt will know much more about female orgasms than any woman is likely to know. Surely you are aware of the importance of sample size in statistics?

As for multiple orgasms though it depends on how one counts. Men can have multiple orgasms as well, there just has to be some little recovery time between them. My record was 6 in an 8 hour period, and I've had 3 or 4 on a number of occasions. That of course was when I was in my 20's, but now that I'm in my late 60's I can still manage 2 a day if I get the right stimulation.

Now that is not to brag, just to state facts which are probably fairly common to sexually active men, but frankly I've never, not once, been with a woman who could manage more than 3 or 4 real orgasms a day, but that depends on how they are counted.

Women do of course manage to have several orgasms with less time in between, but even there things can be deceiving. Sometimes women seem to think that every orgasmic throb or mini crescendo counts as a separate orgasm! Well, men have a whole series of separate orgasmic throbs and mini crescendos during what they count as a single orgasm. They can also have several strong crescendos with intense throbbing prior to ejaculation if they choose to pause at just the right point before continuing. So there is no reason to count every orgasmic female throb as a separate orgasm if we don't do the same for men. So we have to be very careful how things are actually counted. Since the physiology of the female orgasm is not at all clear it is not really easy to decide how to count female orgasms. In my experience, different women report orgasms very differently.

It should be noted that the human female orgasm is not well defined from a scientific basis either. There are several physiological occurrences that can be involved but are not always involved, such as strong clitoral sensation, labia minora engorgement, G spot involvement, Skene's gland secretions, vocalizations and vaginal pulsations. Though women may themselves report orgasms or lack of orgasms during sex, when questioned carefully there is often considerable disparity in those descriptions. So on a scientific basis it is difficult to formally determine whether a woman has an orgasm or not physiologically and even how to define what an orgasm is in women. So basically the problem is the same for human and other animal females which most probably do have orgasms even though some scientists dispute that. It's a subject which hasn't been well studied and is not an easy one to study.

Why assume female animals don't have orgasms? Any such conjecture requires proof. Not having observed a female animal orgasm doesn't imply they don't occur. In fact I believe they do in many cases. I've certainly observed female dogs having apparent orgasms. And of course it all depends on how an orgasm is defined. What physiological responses must be present to constitute an orgasm? That is not a trivial question.

Here's a question for you. When a woman has a G spot orgasm does she also have a simultaneous clitoral orgasm? The theory that the G spot might be part of the clitoris would suggest that. Also in my experience the labia minora often become engorged just prior and during orgasm and the whole vagina will rhythmically contract (serving to squeeze ejaculate through the cervix). Very occasionally I've felt the clitoris throb as well. It seems to me that all these must be considered part of the orgasm and thus that the orgasm can often occur throughout the entire area, in other words it should not be identified only with the clitoris and/or the G spot.

It is correct however that both the male and female orgasm (at least the good ones) is a whole body rather than just a genital event. A good orgasm is a whole body event that may originate in the genitals but radiates through the whole body, refreshing it and flooding it with beneficial hormones and nerve stimuli. In the best orgasms there may be rhythmic contractions of the whole spinal musculature to the extremities (curling toes phenomenon) and the brain may be flooded with feelings of release from all its usual nervous environmental vigilance and entry into a mental state that is very much heavenly, as if one had entered a better world where all was well and healthy and peaceful. Simultaneously the boundaries of the self are felt to dissolve and encompass the lover so that the lovers truly experience themselves as one unified being filled with wonderful glowing energy.

The notion that masturbation conveys the same health benefits as intercourse is just not true. Though both involve orgasm, intercourse (at least when done properly) is a whole body activity that floods the entire body with beneficial hormones and energy, whereas masturbation is mostly just exercising the lower arm. To believe otherwise is close to falling into the fundamental feminist error of equating sex with masturbating in a vagina.

I could go on at considerable lengths on this subject and its relation to Tantric thought, the notion of the energy body and chi, and the work of Wilhelm Reich as presented in his book 'The Function of The Orgasm', but I doubt that those who are still arguing over orgasm 101 would be ready for that yet.... :-)

I haven't read any correlation between ejaculative force and likelihood of conception though I can imagine a mechanism for it being greater hydraulic pressure forcing more semen through the opening in the cervix. However if the seal is tight between penis and vagina I think male piston motion along with greater semen volume would have perhaps more of an effect. Do you have a source for that? There is however considerable evidence that female orgasm increases the chances of conception, since the rhythmic contractions of the vagina in orgasm actually physically act to siphon ejaculate through the cervix. I have in fact seen a video of this occurring and it was quite interesting to observe how the orgasmic contractions actually suck the male's sperm through the opening in the cervix.

Funny, but not very true, that some scientists claim that female orgasm serves no biological function. Unless things have changed since I last checked the penis deposits ejaculate in the vagina, not in the fallopian tubes. Thus any mechanism which assists in transporting it through the cervix will increase the likelihood of conception. The female vaginal orgasmic contractions fulfill that function.

I suspect the notion that women can have multiple orgasms but men can't may be just another feminist urban myth. It needs to be subjected to a genuine scientific analysis. In any case, it is obvious that both men and women have plenty of capacity to enjoy the sexual act.

While my MO is always ladies first, if that doesn't work I always try to help out at the end. It certainly helps to cement a relationship....

EPICANTHIC FOLDS: it is interesting that all babies have epicanthic folds in utero. So rather than seeking an explanation of why certain Oriental populations have them, the proper question should be why have other populations lost them.

INBREEDING AND INCEST: The genetic 'dangers' of incest are vastly overstated, not to mention the false immorality associated with it. There is really only a genetic danger if the family carries certain recessive genes that are specific causes of disease if carried by both parents. That is relatively rare and can be avoided consensually.

Actually there are many advantages to incest. For one thing it can serve to concentrate good genes. Take the Ptolemys of Egypt who ruled for 3 centuries during which brothers and sisters routinely married. After 3 centuries of this was the result a moronic genetic disaster? No, quite the contrary, it was Cleopatra, one of the most brilliant and capable of all ancient rulers. This was so prevalent that some of the Ptolemys included the term 'philopator' (family lover) on their coinage and in their official titles. That it itself puts the lie to incest taboos. There are also a number of other advantages to incest. For one thing it keeps property and power in the family. This was the likely motive of the Ptolemaic dynasty.

The Habsburg dynasty also frequently married close relatives such as uncle-neice, first cousins etc. There were quite a large number of Hapsburgs almost all of which I think showed no greater physical and mental problems than any other royal line so I'm not sure we can jump to conclusions here. See . While it is true that some suffered physical problems, most notably, Leopold the hog nosed, who portraits on his coins clearly show his nasal deformity, such problems appear in the general population as well and need not be the result of inbreeding.

And I was just reading about a remote village in Kerala where first cousins had been marrying since time immemorial which still preserves the DNA markers of the first immigrants out of Africa from 50,000 yBP. There was no mention of any particular of genetic problems in that population. As I've been saying here, morality is entirely relative (pun intended).

Einstein among many others married a cousin (his second wife).

I don't think there is any convincing evidence that such consanguineous unions are generally harmful except in clear cases of specific diseases carried by recessive genes. Thus there is absolutely no reason that incest should be criminalized. It should be entirely the choice of the parties involved, not any government. To do so It is just one more unnecessary societal restriction on sexual freedom.

HOMO FLORESIENSIS: The modern human inhabitants of Flores and surrounding islands say that these diminutive humans still lived there until quite recently and might even still exist today. One tribe told researchers that the last one's they had seen stole a human baby not too many years ago and so the human tribe went up and trapped them all in a cave and burned them to death! Would be tragic if that were really the last of them!

In any case those human tribesmen have quite a few stories about their interactions with the little people mostly about how the little people would steal from them. So science could probably get at least some questions answered by following up on this....

WHY ARE HUMANS SO WEAK AND PUNY? Chimps are known to be 4 to 7 times stronger than humans of the same weight. Human athletic abilities are pathetic in most areas compared to other mammals. The real question here is not why chimps are much stronger than humans but why humans are so much weaker than almost all other animals of comparable size. It's not that chimps are particularly strong relative to most other animals, it's that humans are so much weaker.

One of the few athletic abilities at which humans excel is throwing. Hitting a tennis ball, or wielding a club is an example of this but as for the tennis example, on a small mass like a tennis ball the only thing that matters is the speed of the contacting racket. It's a test of speed not strength. This one ability allowed early humans to greatly magnify their effective strength via the technology of weapons.

VIRGINITY: Blood and pain to me is the antithesis of good sex. I've never 'deflowered' a virgin and glad of it. I don't understand the appeal, or rather I don't experience any such appeal.

WHY DO THE TESTES HANG AT DIFFERENT LEVELS IN HUMAN MALES? There are papers published on this mostly concerned with thermoregulation. However in my opinion the probable answer to the testes question is in that position the testicles take up less sideways space between the thighs in a bipedal posture in which the thighs are placed closer together underneath the trunk for support. Good evidence for that theory is that the different level effect is much more pronounced in bipedal humans where there is less space for the testes to hang due to the upright posture than in males of other quadrupedal species where there is less space restriction.