Sex at Dawn: The Prehistoric Origins of Modern Sexuality (39 page)

Sperm competition is best understood not as a sprint to the egg, but a race over hurdles. Aside from the anti-sperm leucocytes

mentioned

previously,

anatomical

and

physiological obstacles are in the vagina, cervix, and on the surface of the ovum itself. The complexity of the human cervix suggests it evolved to filter the sperm of various males.

Concerning macaques (highly promiscuous monkeys) and humans, Dixson writes: “In the genus
Macaca,
all species of which are considered to have multimale-multifemale mating systems, the cervix is especially complex in structure…. The evidence pertaining to human beings and macaque females,” he continues, “indicates that the cervix acts both as a filtering mechanism and as a temporary reservoir for spermatozoa during their migration into the uterus.”27 As with the complex penis and external testicles in the male, the elaborate filtering design of the human cervix points toward promiscuity in our ancestors.

The idea that female choice (conscious or not) can happen
after
or
during
intercourse rather than as part of an elaborate precopulatory courtship ritual turns the standard narrative inside out and upside down. If the female’s reproductive system has evolved intricate mechanisms for filtering and rejecting the sperm cells of some men while helping along those of a man who meets criteria of which she may be utterly unaware, Darwin’s “coy female” starts looking like what she is: an anachronistic male fantasy.

But Darwin may have suspected more than he let on concerning postcopulatory mechanisms of sexual selection.

Any discussion of human sexual behavior or the evolutionary implications of our genital morphology would have been extremely controversial in 1871, to put it mildly. Just imagine, as Dixson does, “what would have occurred if
The
Descent of Man
had included a detailed exposition of the evolution of the penis and testes or descriptions of the various copulatory postures and patterns employed by animals and human beings.”28

No one can blame Darwin for opting not to include chapters on the evolution of the penis and vagina in his already explosive work. But a century and a half is a long time for discretion and cultural bias to keep smothering scientific fact.

To Meredith Small, the story of the female’s role in conception is a miniature of the overall narrative. She sees the popular understanding of conception as “an outdated allegory of human sexuality” featuring the male as “aggressor, persuader, conqueror.” Recent research on human fertilization suggests something of a role reversal. Small suggests the ovum “reaches out and envelops reluctant sperm.” “Female biology,” she concludes, “even at the level of egg and sperm interaction, doesn’t necessarily dictate a docile stance.”29

In addition to enveloping eggs, a cervix that filters or favors sperm, and vaginal contractions that may expel the sperm of one man while boosting that of another, women’s orgasms provoke changes in vaginal acidity. These changes appear to assist the sperm cells of the lucky guy who provoked the orgasm. The environment at the cervical opening tends to be highly acidic and thus hostile to sperm cells. The alkaline pH

of semen protects the spermatozoa in this environment for a while, but the protection is short-lived; most of the sperm cells are viable within the vagina for only a few hours, so these changes in acidity alter the vaginal environment in ways that can favor sperm that arrive with the female’s orgasm.

The benefits may run both ways. Recent research suggests women who do not use condoms are less likely to suffer from depression than either women who do use condoms or who are not sexually active. Psychologist Gordon Gallup’s initial survey of 293 women (data congruent with those from another survey still to be published that included 700 women) found that women can develop a “chemical dependency” on the boost they get from the testosterone, estrogen, prostaglandins, and other hormones contained in semen.

These chemicals enter the woman’s bloodstream through the vaginal wall.30

If it’s true that multiple mating was common in human evolution, the apparent mismatch between the relatively quick male orgasmic response and the so-called “delayed” female response makes sense (note how the female response is

“delayed” only if the male’s is assumed to be “right on time”). The male’s quick orgasm lessens the chances of being interrupted by predators or other males (survival of the quickest!), while the female and her child would benefit by exercising

some

preconscious

control

over

which

spermatozoa would be most likely to fertilize her ovum.

Prolactin and the other hormones released at orgasm appear to trigger very different responses in men and women. While a man is likely to require a prolonged refractory (or recovery) period immediately after an orgasm (and maybe a sandwich and a beer as well), thus getting him out of the way of other males, many women are willing and able to continue sexual activity well beyond a “starter orgasm.” It’s worth repeating that primate species with orgasmic females tend to be promiscuous. Given the great variability of mating behavior—even just among the apes—this is highly significant. While monogamous gibbons have rarely been seen copulating, so infrequent and silent is their intercourse, female chimps and bonobos go wild regularly and shamelessly. Females often mate with every male they can find, copulating far more than is necessary for reproduction.

Goodall reported seeing one female at Gombe who mated fifty times in a single day.

Echoing the
Kama Sutra,
Sherfey isn’t shy about the implications of this mismatch of orgasmic capacity between human males and females, writing: “The sexual hunger of the female, and her capacity for copulation completely exceeds that of any male,” and, “To all intents and purposes,
the
human female is sexually insatiable.
…” That may or may not be, but it cannot be denied that the design of the human female’s reproductive system is far from what the standard narrative predicts, and thus demands radical rethinking of the evolution of female sexuality.

P A R T V

Men

Are

from

Africa,

Women Are from Africa

The sooner we accept the basic differences between men and
women, the sooner we can stop arguing about it and start
having sex!

DR. STEPHEN T. COLBERT, D.F.A.

Permeating the standard narrative of human sexual evolution is the depressing claim that men and women always have been and always will be locked in erotic conflict. The War Between the Sexes is said to be built into our evolved sexuality: men want lots of no-strings lovers, while women want just a few partners, with as many strings as possible. If a man agrees to be roped into a relationship, the narrative tells us, he’ll be hellbent on making sure his mate isn’t risking his genetic investment by accepting
deposits
from other men, as it were.

Extreme as it sounds, this is no overstatement. In his classic 1972 paper on “parental investment,” biologist Robert Trivers remarked, “One can, in effect, treat the sexes as if they were different species, the opposite sex being a resource relevant to producing maximum surviving offspring.” In other words, men and women have such conflicting agendas when it comes to reproduction that we are essentially
predators
of one another’s interests. In
The Moral Animal,
Robert Wright laments, “A basic underlying dynamic between men and women is mutual exploitation. They seem, at times, designed to make each other miserable.”1

Don’t believe it. We aren’t designed to make each other miserable. This view holds evolution responsible for the mismatch between our evolved predispositions and the post-agricultural socioeconomic world we find ourselves in.

The assertion that human beings are naturally monogamous is not just a lie; it’s a lie most Western societies insist we keep telling each other.

There’s no denying that men and women are different, but we’re hardly different species or from different planets or
designed
to torment one another. In fact, the interlocking nature of our differences testifies to our profound mutuality.

Let’s look at some of the ways in which male and female erotic interests, perspectives, and capacities converge, intersect, and overlap, showing how each of us is a fragment of a greater unity.

CHAPTER TWENTY

On Mona Lisa’s Mind

Do I contradict myself?

Very well then I contradict myself,

(I am large, I contain multitudes.)

WALT WHITMAN,
Song of Myself

Faced with the mysteries of woman, Sigmund Freud, who seemed to have an answer for everything else, came up empty. “Despite my thirty years of research into the feminine soul,” he wrote, “I have not yet been able to answer … the great question that has never been answered: what does a woman want?”

It’s no accident that what the BBC called “the most famous image in the history of art” is a study of the inscrutable feminine created by a homosexual male artist. For centuries, men have been wondering what Leonardo da Vinci’s
Mona
Lisa
was thinking. Is she smiling? Is she angry?

Disappointed? Unwell? Nauseated? Sad? Shy? Turned on?

None of the above?

Probably closer to
all of the above.
Does she contradict herself? Very well, then. The
Mona Lisa
is large. Like all women, but more—like all that is feminine—she reflects every phase of the moon. She contains multitudes.

Our journey into a deeper understanding of the “feminine soul” begins in a muddy field in the English countryside. In the early 1990s, neuroscientist Keith Kendrick and his colleagues exchanged that season’s newborn sheep and goats (the baby sheep were raised by adult goats, and vice versa).

Upon reaching sexual maturity a few years later, the animals were reunited with their own species and their mating behavior

was

observed.

The

females

adopted

a

love-the-one-you’re-with approach, showing themselves willing to mate with males of either species. But the males,
even after being back with their own species for three years,
would mate
only
with the species with which they were raised.1

Research like this suggests strong differences in degrees of

“erotic plasticity” (changeability) in the males and females of many species—including ours.2 The human female’s sexual behavior is typically far more malleable than the male’s.

Greater erotic plasticity leads most women to experience more variation in their sexuality than men typically do, and women’s sexual behavior is far more responsive to social pressure. This greater plasticity could manifest through changes in whom a woman wants, in how much she wants him/her/them, and in how she expresses her desire. Young males pass through a brief period in which their sexuality is like hot wax waiting to be imprinted, but the wax soon cools and solidifies, leaving the imprint for life. For females, the wax appears to stay soft and malleable throughout their lives.

This greater erotic plasticity appears to manifest in women’s more holistic responses to sexual imagery and thoughts. In 2006, psychologist Meredith Chivers set up an experiment where she showed a variety of sexual videos to men and women, both straight and gay. The videos included a wide range of possible erotic configurations: man/woman, man/

man, woman/woman, lone man masturbating, lone woman masturbating, a muscular guy walking naked on a beach, and a fit woman working out in the nude. To top it all off, she also included a short film clip of bonobos mating.3

While her subjects were being buffeted by this onslaught of varied eroticism, they had a keypad where they could indicate how turned on they felt. In addition, their genitals were wired up to Plethysmographs.
Isn’t that illegal?
No, a plethysmograph isn’t a torture device (or a dinosaur, for that matter). It measures blood flow to the genitals, a surefire indicator that the body is getting ready for love. Think of it as an erotic lie detector.