Kim, who is notoriously obsessed with her vagina, sent me a link about this very interesting evolutionary moment, when apes switched from quadrupedalism to bipedalism, and how it changed the sexual aspect of their bodies (by ‘their’ i mean ‘our’, and by ‘bodies’ i mean ‘between the legs’).

Inaccessible and concealed external female genitals are one of the morphological characteristics distinguishing humans from other higher primates.

External female sexual organs in subhuman primates are visible and accessible in the habitual quadrupedal and occasional bipedal posture, whereas these organs in the human female are inaccessible and concealed in any posture. A prospective consequence of gradual bipedalism of hominids during evolution was a shifting of the external female genitals in an anterior direction. In the completely bipedal Homo sapiens, this resulted in the vulvo-cryptic phenomenon, i.e. concealed female genitals in humans.

The unique morphology of the human female pelvis served as an obstacle to easy access of the male in the process of copulation, necessitating the female’s conscious decision for sexual intercourse. This circumstance might have created a psychological basis for female propellant psychosexual manipulation of the male as a natural consequence.

Also, through the process of positive selection it could have formed a basis for linking reproductive success with the development of cognitive and emotional capacities. Female consent to copulation is a conscious and complex act that would be impossible without the involvement of highly developed emotional-cognitive and memoric brain systems.

Thus the extraordinary evolutionary strategy might imply a teleological link between concealed female genitals and the emotional-cognitive characteristics of man, creating a permanent promoter of further development of emotional and cognitive brain systems with an impact on all domains of everyday life.

Male apes used to have tiny genitals hidden in the quadrupedal posture. On the other hand, females sexual organs were visible (and accessible — think about the impressive vaginal swellings of chimpanzee females). This means that before apes became modern humans, the female “desire” was visible, while the male one was concealed.

So when apes switched from quadrupedalism to bipedalism, the swollen external female genitals shrunk to the tiny human female labia, went hidden behind the pubic hair and between the legs, and became concealed in any posture (aka the vulvo-cryptic phenomenon). Also, the smells that signal fertility became nearly imperceptible.

While the female shifting went in an anterior direction, the male shifting went the opposite way: by walking upright, the male showed his (bigger) penis.

Studies indicate that, aside from its functions as a visual signal, the female chimpanzee’s sexual skin swelling adds considerably to the distance males must negotiate during copulation to place spermatozoa at the cervical os. Evolution of the male’s elongated, filiform penis may therefore be the result of sexual selection, to negotiate the long vagina of the female and to penetrate copulatory plugs deposited during previous copulations.

Also: female apes didn’t have any boobies. And both males and females were hairy. They were distinguishable by their size (males could weigh up to three times as much as the females). Men and women are less easy to distinguish by their size, so women’s breast and men’s bigger genital aid in recognition of the opposite sex.

So now the male’s genitals are visible, and the woman’s genitals are invisible (unless she spreads her legs).

Male apes used to “read” the (visible and accessible) female genitals to see if the female was in heat. Not anymore. Modern men now have to read the face of the woman. That’s a big shift.

{ stereo hell | thanks Imp }

photo { Kate Moss by Terry Richardson }

Breasts in human are what scientists call “a sexually dimorphic trait,” one that exists in two different forms in the males and females of the same species. Another example of sexually dimorphic trait (or sexual dimorphism) is the beautiful plumage of the peacock in comparison to the dull feathers of the peahen. (…)

Human female breasts became sexual signals to attract males. Females with this trait would have increased mating opportunities, thereby passing the genes for permanently enlarged breasts on to subsequent generations.

Desmond Morris, a curator of mammals at the London Zoo, suggested that permanently enlarged breasts in human females resulted from hominid bipedalism. (…)

The link between bipedalism and permanent breast enlargement, according to Morris, has to do with the erotic nature of breasts. He argues that as early humans (hominids) began walking upright, face-to-face encounters between the sexes became the norm, affecting the position used in sexual intercourse: males would no longer mount females from behind as they do among non-human primates. In the non-human primate position, presentation of the female buttocks to the male is an erotic display that stimulates male interest and excitement. With the advent of bipedalism, Morris argues, if females were to be successful in shifting male interest around to the front, evolution would have to do something to make the female frontal region more stimulating to males. This was accomplished, Morris says, through self-mimicry in which female breasts came to look like rounded buttocks: female breasts became mimics of “the ancient genital display of the hemispherical buttocks.”

Szalay and Costello (1991) have continued this line of thinking, but argue that permanently enlarged breasts sexually arouse males not because they look like buttocks, but because they mimic the appearance of female genitalia.

Other theories focus on the role breasts played thousands of years ago in enticing a male to stick around after the birth of his children, ensuring his parental investment in them. (…)

Sociobiologists and evolutionary psychologists claim that to keep the male around, women have developed a number of traits and behaviors. One set of behaviors, for example, is known as the “domestic-bliss strategy,” which involves a woman playing “hard to get” in the mating game. By being “coy” and holding out on sex, sociobiologists and evolutionary psychologists claim, the female is likely to attract a male willing to wait for sex. (…)

For sociobiologists and evolutionary psychologists, enlarged breasts are just another weapon in a female’s arsenal for attracting a man and keeping him around. Cant (1981) suggests that breasts became signals alerting a male to which female would be more likely to raise his offspring successfully. Cant argues that females better able to build up fat and maintain it would have more reserves to convert to parental investment during pregnancy and lactation. Since breasts are primarily composed of fat, Cant argues that they became an indicator of the nutritional status of the female.

These theories stress how keeping a man around saved the human species from extinction.

{ Frances E. Mascia-Lees | Continue reading }

illustration { Booborama | enlarge }

related { Almost a third of all apes, monkeys and other primates are in danger of extinction }

READ MORE >> ideas, science, animals, flashback, sex-oriented | October 26th, 2007