Sex & God: How Religion Distorts Sexuality (14 page)

Ducks have a lot of sex. A female takes a liking to a certain male and waddles around in a seductive way to get his attention. Her behavior shows that she wants to mate with a specific male, but every male wants in on the act. She mates with her beau, then the others try to gang on. Though she struggles to escape, she is no match for three or four males at once. It is rape, pure and simple, and she doesn’t like it.

For years this behavior was a mystery to scientists. Questions like, “Why is there so much rape among ducks?” “Does the female have any real control over who she mates with?” and “Why do ducks have large penises?”

Dr. Patricia Brennan at the University of Sheffield, England, is an expert on duck sex. Thank goodness we have duck-sex workers. She unveiled the mystery of duck mating as summarized below.

The duck penis is amazingly large for such a small animal, often as long as the duck, and male ducks grow a new penis every mating season. Why carry that big thing around if you don’t need it.
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The male penis resides inside the bird and “everts” out in one third of a second. Eversion is like an erection, only inside out. When the duck is ready to mate, he pushes it out, like blowing a balloon out of his body.

When males are in large groups with other males, they grow their penises 15-25% longer.
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If the competition is too tough, the less dominant males grow more moderate penises and start to absorb them back into their body weeks earlier than the males with huge members. Their chances for reproduction are slim in the face of competition, so they reabsorb their penises and hope for better luck next year.

According to Dr. Maydianne Andrade of the University of Toronto-Scarborough, “Ducks are essentially engineering their own phallus in response to social challenges.”
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For decades, biologists marveled at the huge penises on such small animals. No one could come up with a good explanation for the duck penis that fit all the facts, until Dr. Brennan decided to do something radical; she dissected the female reproductive tract. Seems the male scientists had never bothered to look at the female. To her surprise, Dr. Brennan found that the female tract was extremely deep and shaped like a corkscrew, only in the opposite direction from the male (which would make it hard for the male to mate). There were dead-end pockets, where semen could get caught and not make it up to the eggs. Brennan’s experiments showed that the female can relax her reproductive tract and make it easy for a male to get in or she can “corkscrew” it to make it difficult. In the evolutionary battle over who gets to fertilize the egg, the males had the brute force, but the females had an effective resistance strategy.

On the male side, experiments showed that the male can get his penis up and put it in and ejaculate amazingly fast. Now it all makes sense. This is not just a war of the sexes; it is a war between the sex organs. Dr. Brennan hypothesized that this system has co-evolved to help the male penetrate and mate fast and help the female resist such rapid mating without her permission. To determine if the female has control over who actually fertilizes her eggs, Dr. Brennan did DNA testing on ducklings and found that 97% of all fertilized eggs were by the guy Ms. Duck liked.

Looking at a wide variety of duck species, researchers have shown that this is not a finished fight. Different species seem to be in different stages of this co-evolution. Depending on the mating strategy, male and female sex organs may have different shapes and sizes. This is called sexually antagonistic co-evolution, and it is found in many terrestrial species.

We can find many examples of sexually antagonistic co-evolution among spiders, insects, rabbits and hyenas. A study of 15 species of water striders showed that each had evolved strategies for male mating and female mate prevention. Each species has its own unique solution to the problem of how to mate, who to mate with and how to control the mating process.

Looking closely at all aspects of the reproductive organs and reproductive cycle in a species tells a lot about the current state of sexual competition, where it was in the past and, perhaps, how it got to the place it is now. Armed with the concept of sexual competition and antagonistic co-evolution, we can turn our attention to species more closely related to us and ask, “What does their sexual physiology and reproductive cycle tell us? Where are they now and how did they come to the current state?” We are going to explore a series of facts and then see where they point us.

Among most mammals, size difference between male and female is a good predictor of polygyny
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in that species. The larger the size difference, the more females a male will mate with and try to control. Size difference between the sexes is known as sexual dimorphism.

Among all primates, gorillas have the greatest degree of sexual dimorphism. For gorillas, it is body size that counts. An adult male mountain gorilla may weigh 220 kg (484 lb) and a female, 97.7 kg (215 lb). Thus, the male is twice the size of the female. But the male’s penis is only 4 cm (1.5 in) long.

Gorillas also have a baculum or penis bone. The baculum is a bone in the penis that assists in mating. Most mammals have a baculum including all primates, except humans. A few other species have also lost their baculum: elephants, horses, whales and dolphins, to name a few.

A silverback male gorilla generally has a harem of two to five females with whom he has exclusive mating rights even if other “black back” (immature) males are present. While the male guards his females from other silverbacks, a female is free to leave and join another group whenever she wants. The average female changes groups two or three times in her lifetime. She may even go off and mate with a single male. Actual sex among gorillas only lasts about a minute, so a quick dalliance can be pulled off easily if the conditions are right.

The largest male usually dominates the local group, which can be as big as 20-30 individuals. While silverbacks rarely fight to the death, they do put on an impressive show of force to convince any potential usurpers to back off.

Females generally leave their home troop when they are about 7 or 8 years old in search of a silverback that they might move in with. While they may be sexually mature at that age, they often don’t begin mating until they are 12–14 years old. By comparison, males leave their troop when they reach 10 or 11. Males often lead a solitary life until they can attract their own females and begin mating at 15 to 18 years old. There is a lot of competition in the gorilla world for females. Not every male will establish a harem. Those who cannot may join a group as a submissive male with no mating privileges, or they may continue to live alone.

Gorillas are at the opposite end of the penis spectrum than ducks. As long as they have imposing physical size, gorillas do not need to have a large penis. Gorillas also have sex far less frequently than the three other great apes (chimps, bonobos and humans). As a result, a male doesn’t need to produce as much sperm, and his testes are less than half the size of humans’ and a quarter the size of chimps’.

Compared to gorillas, chimps are extremely sexual. Females may mate several times a day. When the female is ovulating, her sex organs swell and become pink, advertising the fact. A female in estrus (commonly called “heat”) attracts the attention of every male in the troop, but while chimp females are very sexual, they don’t mate randomly. The top males get most access and they only mate when in estrus. Males of lower rank may or may not get to mate.

Alpha males may attain their position through intelligence and social skill. For example, a male that can put together an alliance of males may dominate the group through sheer force of will and intelligence. Jane Goodall, in her book
In the Shadow of Man
(1971), tells the story of Mike, a low-ranking male who spent years on the outer edge of the group. One day he discovered the power of empty gasoline cans. Picking them up, making a display, then running with the cans in hand or pushing them, he found that he could intimidate all the other males. It took Mike about four months to ascend to his throne as the alpha male of the group.

Chimp sexual anatomy contrasts sharply with that of gorillas. First of all, the chimp penis is much larger and longer, 8 cm (3 in.). Chimps also have very large testes, twice as large as humans’. With all that sex, they need to produce a lot of semen. Males can mate many times a day but are only interested in females who are in estrus, as the naturalist Carly Wilson has noted:

Chimps have giant balls, the biggest of any primate and twice the size of the average man … They use these giant balls to produce in excess enough semen to flush out the lingering semen of any males to which their partners may have recently mated. In essence, male chimps have big balls because female chimps are whores. Ouch. To be fair, the males are whores, too though.
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To go a step farther into semenology, within the semen of chimps is a substance that forms a plug.
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This plug, formed by a protein that coagulates,
prevents subsequent males’ sperm from fertilizing the egg. Many species use this strategy.
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With all the sex going on among chimps, a male has to have a way to stop other males from getting to the egg.

This is called sperm competition. There are two kinds of sperm competition. The first is simply producing more sperm than the other guy. The second is having a method for preventing the other guy from getting to the egg. The plug is one part of the prevention strategy.

But there is another layer to sperm competition. While the sperm may be fighting and plugging away, the semen from the second guy contains a liquefying agent known as PSA that can dissolve a plug from the first donor and allow the second donor’s sperm to get on with the race. How is that for a fight? It’s an entire war going on inside the female chimp and an entire level of evolutionary pressure independent of the size of the animal, shape of the penis or reproductive details of the female.

Following the biology of chimps and discovering the highly developed sperm competition system probably means there has been a lot of mating going on between females and multiple males for thousands of generations. “Follow the biology” tells the story of what is really going on in a species’ mating strategies.

Mating strategies are often very different even between closely related species, and the bonobo are very different from the gorilla and the chimp. The bonobo is the smallest and rarest of the four great apes. It was once thought to be a chimp and was commonly called the pygmy chimp because it was about 10% smaller, but DNA evidence shows that bonobos are actually a different species.

Bonobos seem more human than chimps. For example, while chimps prefer sex doggy-style, bonobos greatly prefer face-to-face, missionary style. Bonobos even like to kiss, and they are not too concerned about what gender they are having sex with. Frans de Waal, the great Dutch primatologist,
notes his student’s astonishment when he shows them a video of two male bonobos giving each other a long French kiss.
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Imagine a fundamentalist church taking a field trip to the zoo to give a lesson in creationism and coming across a couple of bonobos gazing into one another’s eyes while having sex and kissing. It might throw a monkey wrench into the lesson plans.

Sex is far more important as a bonding, tension reliever and conflict management tool than for procreation. When two bonobos get into conflict, they often end up rubbing genitals or having sex to dissipate the tension or conflict. When a bonobo finds a particularly good fruit tree or food source, he or she gets very excited and often has sex with another bonobo before settling down to eat. When nervous tension is present in the group, many engage in tension-releasing sex.

Bonobos have sex frequently and with many partners. In bonobo culture, females rule. A committee of closely allied females makes sure the male testosterone doesn’t get out of control. When a male tries to over-assert himself, the top two or three females gang up on him to let him know where he stands. When food is found, the top females get the prime picks while the sons and daughters of high-status females are next in line.

In the bonobo world, the female leaves her natal group to wander out to find another. She joins a new group by finding one of the senior females and approaching her sexually. This takes the form of rubbing clitorises and grooming the senior female. If the younger female is accepted, the two will bond. All females in the group are bonded to each other more than to any male, and the bonding activity continues throughout life. Females may have as much or more sex with each other as with males.

Males, on the other hand, stay with their birth group and maintain a strong bond with their mothers. Sons of high-status mothers will have high status, but the female always is in the alpha position.

The female clitoris is enormous, the size of a little finger. Bonobos seem to get a great deal of enjoyment out of clitoral stimulation, including orgasm. According to Frans de Waal, the expression on female bonobos looks very similar to human females when they are having an orgasm, including clenched teeth and an expression of intense concentration.
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They also engage
in a wide variety of hand-to-genital stimulation with themselves and others. Every combination of masturbation and sex has been observed and all are frequent enough to be a normal part of sexual expression.

Unique among mammals, bonobos have semi-hidden estrus. Only humans have a similar strategy. Most mammals mate only when they are in heat or fertile, but bonobos seem to mate any time. When females are in estrus, they display more pink genitals, but this sign of fertility is not an invitation to have lots of sex (like chimps) since they are already having lots of sex.