Sex & God: How Religion Distorts Sexuality (15 page)

When a female bonobo becomes pregnant and gives birth, she generally cares for her baby for four to five years and does not conceive again until the baby is weaned. But the sex goes on. It is the same in humans. As long as a woman is nursing, her fertility cycle usually will be suppressed. It’s nature’s way of saying, “Don’t have another baby until this one is able to take care of itself.” Because modern women do not nurse as long or as much, they become fertile much sooner after a pregnancy than our hunter-gatherer ancestors and bonobos.

Bonobo anatomy is interesting for its differences and similarities to other primates. Like chimps, the penis is large relative to body size and has a baculum (penis bone). Like humans, the females have breasts. They are small, but clearly present compared to the flat-chested chimps. Male testes are very large and produce copious amounts of semen, presumably to flush out and compete with the semen of other males who went before. And, as in the chimp, bonobo semen has the same methods for blocking and fighting other sperm. Bonobos are also the masters of the “quickie.” A typical sexual encounter lasts as little as 7-15 seconds.
⁶⁹

Comparing gorilla, chimp and bonobo sex, we can see a spectrum of sexual strategies from the gorilla’s highly male-dominated polygynous system, to the chimp’s male-dominated multimate system, to the highly female-oriented multimate bonobo system. These three species are genetically tied to a particular sexual strategy for their species.

What were humans doing 20,000 years ago when all of humanity were hunters and gatherers? There are hints at our previous sex lives in our genes,
physiology and anatomy. For example, human males have testes that are far larger than those of the polygynous gorilla but half the size of the highly sexual chimp and bonobo. Humans produce a large amount of semen compared to the gorilla but not nearly as much as the bonobo or chimp. What might that say about our sexual tendencies in the past and now?

Just like the bonobo, humans have a hidden estrus and can mate at any time, indicating that sex serves more of a social bonding than a reproduction role. The sexual dimorphism and larger testes point to a polygynous tendency, or multimate strategy, and counter any idea that humans are monogamous. The female breasts are totally puzzling in terms of evolutionary causes, but we can be sure they are important and sexually selected in our history because they attract so much attention from both men and women.

Human females are strongly affected by their biology in the type of male they prefer. For years, researchers got conflicting results on the types of bodies and faces that women found attractive. Johnston and colleagues cracked the puzzle when they took into account where a woman was in her menstrual cycle.
⁷⁰
During fertility, women preferred very masculine faces. When they were not fertile, women preferred more feminine faces. In other research, Hughes and Gallup found that male shoulder-to-hip ratio was predictive of sexual activity at a younger age, with more partners and extra pair couplings.
⁷¹
Apparently, women find this male body type very attractive. All of this gives a strong indication that women and men are unconsciously driven by their biology.

The human penis does not have a baculum (penis bone) and is totally dependent upon a pressurizing system to get an erection. With a baculum bone, a male can easily get an erection. Without it, a human male has to be in good health in order to get an erection. As with many traits in nature, females often select the male who shows the best “health traits.”

The human penis is far larger than in other primates, both in absolute size and relative to body size. What would cause this larger size in humans? Geoffrey Miller in his book,
The Mating Mind
(2001), writes:

Given two otherwise identical hominid males, if female hominids consistently preferred the one with the longer, thicker, more
flexible penis to the one with the shorter, thinner, less flexible one, then the genes for large penises would have spread. Given the relatively large size of modern human penis, it is clear that size mattered. If it had not, modern males would have chimp-sized sexual organs. … 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.

Another theory is that the penis evolved along with the vagina. As the human head got larger, the birth canal also had to enlarge, hence the penis enlarged as well.

Besides size, the human penis is shaped differently from those of the other great apes. The glans or penis head is enlarged, giving it a mushroom-type shape at the top. This shape is so distinct and different from other primates as to suggest some important evolutionary function. The differences between human and other primate penises indicate that some level of competitive pressure drove the change since we split from the chimp/bonobo line around 4.1 million years ago. But why this particular shape? What benefit might it confer to the owner?

Robin Baker, biology professor at the University of Manchester, England, found that the penis shape serves perfectly as a pump – to pump semen out of the vagina!
⁷²
The penis can pump up to 80% of semen out of the vagina, removing semen from any previous mate. This simple fact of penis shape as a pump explains several other things. Why does human copulation last so much longer compared to that of other primates? A chimp or bonobo is finished in 7-15 seconds and gorillas in one minute, whereas humans go for four minutes or longer.
⁷³
While pleasurable for both parties, it allows the man enough time to pump out the previous fellow’s semen before depositing his own. Once ejaculation happens, the human male goes flaccid rapidly so as not to pump his own semen out.

Following up on Baker’s research, Gallup and Burch of the State University of New York found:

The displacement of simulated semen was robust across different prosthetic phalluses, different artificial vaginas, different semen
recipes, and different semen viscosities. The magnitude of semen displacement was directly proportional to the depth of thrusting and inversely proportional to semen viscosity. By manipulating different characteristics of artificial phalluses, the coronal ridge and frenulum were identified as key morphological features involved in mediating the semen displacement effect.
⁷⁴

Going beyond penis anatomy, the ejaculate of human males shares with chimps (and other animals) the ability to coagulate. Some researchers have noted that semen coagulates within seconds after ejaculation.
⁷⁵
This may serve to keep semen in place while sperm make their way to the egg and/or it may serve to prevent other sperm from getting to the egg. While humans do not make as strong a semen plug as chimps and bonobos, human semen does create an obstruction.

Why would evolution reshape the penis, enlarge the testes, eliminate the baculum bone and create semen plugs? Because humans are a polygynous species and may be a multimale, multifemale species. This may sound radical, but genetic evidence shows that about 80% of women have reproduced throughout our history but only 40% of men.
⁷⁶
This stunning fact means that over time, women have been more successful at reproducing than men and that successful men have reproduced with two or more women. While this may seem to go against common sense, we must remember that over history, men have consistently had the most dangerous positions in society. Even today, 93% of the people killed on the job are men. It was undoubtedly worse with our hunter-gathering ancestors as well as the warrior cultures of later civilization. In the course of our species, many young men died before they could reproduce. In addition, the men at the top of almost any society have access to more women than the men at the bottom (the Hugh Hefner effect). Human females are also more attracted to high-status men.

All of these facts, penis shape and size, loss of baculum bone, larger testes, longer coitus, point to adaptations in response to intense reproductive pressure on men. Human male sex organs evolved in a highly competitive environment that involved a multimate system. Women evolved attraction to certain types of males, men evolved strategies to displace other male’s sperm and ensure their sperm gets to the egg first – to name just a few of the evolved characteristics. It is a dance between males and females, between male sex organs and female sex organs, between male semen chemistry and female vaginal chemistry. The result is a mating strategy that resembles other primates in some ways, but is unique to our species.

For decades, researchers could not understand how men could report far more sexual partners than women. Some suspected that men exaggerated; others suspected women underreported. The mystery was solved when Alexander and Fisher
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found that women reported far fewer sexual partners when they thought their answers might be seen by a researcher. They reported more partners when they thought their answers were anonymous and even more when they thought they were hooked up to a lie detector machine. Under the “lie detector” condition, women’s answers were equal to those of men. Men’s answers did not vary. The researchers attributed underreporting to the social expectation of purity placed upon women in our culture.

Over the last 60 years, vast amounts of research have been conducted on human sexuality and behavior. Depending on the study, 90-95% of all people have had sex before marriage and most of those with partners they do not ultimately marry. In addition, Kinsey found that 50% of men and 26% of women had extramarital affairs.
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Then we must consider that 50% of couples get divorced and most go on to have sex with one or more people before they marry again. While it is difficult to determine exact numbers, there is no doubt that a high proportion of people have multiple sex partners in a lifetime.

Humans are not now – and never have been – monogamous. According to the research, humans have been a multimate species for millions of
years. At best we are serial polygamists (one mate with two or more mates, without regard to sex of the partner), bonding with someone for a time and then moving on to other mates.
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“Follow the biology" tells us much more about who we are than any religion. If you want more information, take a look at some of the books or studies in the bibliography.
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Next, we will look at how biology, among other things, affects our development into unique sexual human beings.

59
One critic, botanist Johann Siegesbeck, called Linnaeus's plant classification system a “loathsome harlotry.” See
http://www.ucmp.berkeley.edu/history/linnaeus.html
.

60
See a brief listing of articles by Brennan, et al, at
http://www.yale.edu/eeb/prum/evolution.htm
.

61
Also see a review of Brennan's studies by Susan Milius in
Wired
magazine, August 2010. Available online at
http://www.wired.com/wiredscience/2010/08/duck-penises/
.

62
Ibid.

63
Polygyny: many wives. It is often called polygamy in modern culture. The opposite, many husbands, is termed polyandry. Although these terms are related to the idea of marriage, we will use the term polygyny in relation to this discussion even though animals don’t marry and most are not even monogamous, as we will see later.

64
From Wilson's blog, available at
http://carlywilson.com/2010/08/free-love-in-the-animal-kingdom/
.

65
Kingan, et al, (2003). “Reduced Polymorphism in the Chimpanzee Semen Coagulating Protein, Semenogelin I.”
Journal of Molecular Evolution
, 57:159–169. Available online at
http://www.oeb.harvard.edu/faculty/edwards/people/postdocs/papers/Kingan2003.pdf
.

66
In many polyandrous species (mates with many males), the males tend to carry a couple of genes that allow the semen to create a plug. Only in a species where there are multiple male partners would such a gene be useful. Bonobos and chimps have these genes (SEMG1 and SEMG2), and so do humans.

67
Noted in de Waal's
Our Inner Ape
, (2005), p. 90.

68
Ibid., p. 95.

69
See Jared Diamond's
The Third Chimpanzee: The Evolution and Future of the Human Animal
, (2006), p. 75.

70
Johnston, V. S., Hagel, R., et al. (2001). “Male facial attractiveness: Evidence for Hormone-Mediated Adaptive Design.”
Evolution and Human Behavior
, 22(4).

71
Hughes. S. M., Dispenza, F., and Gallup, J. G. G. (2004). “Ratings of Voice Attractiveness Predict Sexual Behavior and Body Configuration.”
Evolution and Human Behavior
, 25.

72
For a explanation by Robin Baker on this phenomenon, see the video available online at
http://www.robin-baker.com/videos/v2/

73
Noted in Diamond's
The Third Chimpanzee
, p. 75.

74
Gallup, G.G. and Burch, R.L., (2004). “Semen displacement as a sperm competition strategy in humans.”
Evolutionary Psychology
, 2.

75
As noted previously, in Kingan, et al, 2003 article “Reduced polymorphism in the chimpanzee semen coagulating protein,” as well as studies by Dixson and Anderson, (2002), “Sexual selection, seminal coagulation and copulatory plug formation in primates.” (
Folia Primatologica; International Journal of Primatology
, 73(2-3)) and by Dorus, Wyckoff, et al., (2004), “Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity.” (
Nature Genetics
, 36).

76
Roy Baumeister, “Is There Anything Good About Men?” American Psychological Association, Invited Address, 2007. Transcript available online at
http://www.psy.fsu.edu/~baumeistertice/goodaboutmen.htm
.