Sex at Dawn: The Prehistoric Origins of Modern Sexuality (35 page)

Just as eyeglasses have allowed survival and reproduction for people with visual incapacities that would have doomed them (and their genes) in ancestral environments, sexual monogamy permits fertility-reducing mutations to proliferate, causing testicular diminishments that would never have lasted among our nonmonogamous ancestors. The most recent estimates show that sperm dysfunction affects about one in twenty men around the world, being the single most common cause of subfertilility in couples (defined as no pregnancy after a year of trying). Every indication is that the problem is growing steadily worse.12 Nobody’s maintaining the spare fridge much anymore, so it’s breaking down.

If our paradigm of prehistoric human sexuality is correct, in addition to environmental toxins and food additives, sexual monogamy may be a significant factor in the contemporary infertility crisis. Widespread monogamy may also help explain why, despite our promiscuous past, the testicles of contemporary
Homo sapiens
are smaller than those of chimps and

bonobos

and,

as

indicated

by

our

excess

sperm-production capacity, than those of our own ancestors.

Sexual monogamy itself may be shrinking men’s balls.

Perhaps we can declare an end to the standoff between those who argue that small human testicles tell “a story of romance and bonding between the sexes going back a long time, perhaps to the beginning of our lineage,” and those who contend

that

our

slightly-larger-than-they-should-be-if-we’re-really-monogamous testicles indicate many millennia of “mild polygyny.” Humans

have

medium-size

testicles

by

primate

standards—with strong indications of recent dwindling—but can still produce ejaculates teeming with hundreds of millions of spermatozoa. Along with a penis adapted to sperm competition, human testicles strongly suggest ancestral females had multiple lovers within a menstrual cycle. Human testicles are the equivalent of drying apples on a November tree—shrinking reminders of days gone by.

As a way of testing this hypothesis, we should find that relative penis and testicle data differ among racial and cultural groups. These differences—theoretically due to significant and consistent differences in the intensity of sperm competition in recent historical times—are what we do find, if we dare to look.13

Because fit is so important in the effectiveness of condoms, World Health Organization guidelines specify different sizes for various parts of the world: a 49-millimeter-width condom for Asia, a 52-millimeter width for North America and Europe, and a 53-millimeter width for Africa (all condoms are longer than most men will ever need). The condoms manufactured in China for their domestic market are 49

millimeters wide. According to a study conducted by the Indian Council of Medical Research, high levels of slippage and failure are due to a bad fit between many Indian men and the international standards used in condom manufacture.14

According to an article published in
Nature,
Japanese and Chinese men’s testicles tend to be smaller than those of Caucasian men, on average. The authors of the study concluded that “differences in body size make only a slight contribution to these values.”15 Other researchers have confirmed these general trends, finding average combined testes weights of 24 grams for Asians, 29 to 33 grams for Caucasians, and 50 grams for Africans.16 Researchers found

“marked differences in testis size among human races. Even controlling for age differences among samples, adult male Danes have testes that are more than twice the size of their Chinese equivalents, for example.”17 This range is far beyond what average racial differences in body size would predict.

Various estimates conclude that Caucasians produce about twice the number of spermatozoa per day than do Chinese (185–235
×
106 compared with 84
×
106).

These are dangerous waters we’re swimming in, dear reader, suggesting that culture, environment, and behavior can be reflected in anatomy—genital anatomy, at that. But any serious biologist or physician knows there are anatomical differences expressed racially. Despite the hair-trigger sensitivity of these issues,
not
to consider racial background in the diagnosis and treatment of disease would be unethical.

Still, some of the reluctance to connect culturally sanctioned behavior with genital anatomy is as much due to the difficulty of finding reliable historical information about true rates of female promiscuity as to the emotionally charged nature of the material itself. Furthermore, diet and environmental factors would have to be factored in before arriving at any solid conclusions regarding the relationship between sexual monogamy and genital anatomy. For example, many Asian

diets include large quantities of soy products, while many Western people consume large quantities of beef, both having been shown to cause rapid generational reduction in testicular volume and spermatogenesis. Given the controversial nature of such research, and the complexities of eliminating so many variables, perhaps it’s not surprising that this is an area few researchers are eager to enter.

There is a wide world of evidence that human sexual activity goes far beyond what’s needed for reproduction. While the social function of sex is now seen mainly in terms of maintaining the nuclear family, this is far from the only way societies channel human sexual energies to promote social stability.

Coming in at hundreds or thousands of copulations per child born, human beings outcopulate even chimpanzees and bonobos—and are far beyond gorillas and gibbons. When the average duration of each copulation is factored in, the sheer amount of time spent in sexual activity by human beings easily surpasses that of any other primate—even if we agree to ignore all our fantasizing, dreaming, and masturbating.

The evidence that sperm competition played a role in human evolution is simply overwhelming. In the words of one researcher, “Without sperm warfare during human evolution, men would have tiny genitals and produce few sperm….

There would be no thrusting during intercourse, no sex dreams or fantasies, no masturbation, and we would each feel like having intercourse only a dozen or so times in our entire lives…. Sex and society, art and literature—in fact, the whole of human culture—would be different.”18 We can add to this list the fact that men and women would be the same height and weight (if monogamous) or that men would likely be twice the size of women (if polygynous).

Just as Darwin’s famous finches in the Galápagos evolved different beak structures for cracking different seeds, related species often evolve different mechanisms for sperm competition. The sexual evolution of chimps and bonobos followed a strategy dependent upon repeated ejaculations of small but highly concentrated deposits of sperm cells, while humans evolved an approach featuring:

• a penis designed to pull back preexisting sperm, with extended, repeated thrusting;

• less frequent (compared to chimps and bonobos) but larger ejaculates;

• testicular volume and libido far beyond what’s needed for monogamous or polygynous mating;

• rapid-reaction DNA controlling development of testicular tissue, this DNA apparently being absent in monogamous or polygynous primates;

• overall sperm content per ejaculate—even today—in the range of chimps and bonobos; and

• the precarious location of the testicles in a vulnerable external scrotum, associated with promiscuous mating.

In Spanish, the word
esperar
can mean “to expect” or “to hope”—depending

on

context.

“Archaeology,”

writes

Bogucki, “is very much constrained by what the modern imagination allows in the range of human behavior.”19 So is evolutionary theory. Perhaps so many still conclude that sexual monogamy is characteristic of our species’

evolutionary past, despite the clear messages inscribed in every man’s body and appetites, because this is what they
expect
and
hope
to find there.

CHAPTER EIGHTEEN

The Prehistory of O

Now there you have a sample of man’s “reasoning powers,”
as he calls them. He observes certain facts. For instance, that
in all his life he never sees the day that he can satisfy one
woman; also, that no woman ever sees the day that she can’t
overwork, and defeat, and put out of commission any ten
masculine plants that can be put to bed to her. He puts those
strikingly suggestive and luminous facts together, and from
them draws this astonishing conclusion: The Creator
intended the woman to be restricted to one man.

MARK TWAIN,
Letters from the Earth

We recently spotted a young man strolling down Las Ramblas in Barcelona proudly sporting a T-shirt proclaiming that he was
Born to F*ck.
One wonders whether he has a whole set of these shirts at home:
Born to Bre*the, Born to E*t, Born to
Dr*nk, Born to Sh*t,
and of course the depressing but inevitable
Born to D*e.

But maybe he was making a deeper point. After all, the argument central to this book is that sex has long served many crucial functions for
Homo sapiens,
with reproduction being only the most obvious among them. Since we human beings spend more time and energy planning, executing, and recalling our sexual exploits than any other species on Earth, maybe we all should wear such shirts.

Or maybe just the women. When it comes to sex, men may be trash-talking sprinters, but it’s the women who win all the marathons. Any marriage counselor will tell you the most common sex-related complaint women make about men is that they are too quick and too direct. Meanwhile, men’s most frequent sex-related gripe about women is that they take too damned long to get warmed up. After an orgasm, a woman may be anticipating a dozen more. A female body in motion tends to stay in motion. But men come and go. For them, the curtain falls quickly and the mind turns to unrelated matters.

This symmetry of dual disappointment illustrates the almost comical incompatibility between men’s and women’s sexual response in the context of monogamous mating. You have to wonder: if men and women evolved together in sexually monogamous couples for millions of years, how did we end up being so incompatible? It’s as if we’ve been sitting down to dinner together, millennium after millennium, but half of us can’t help wolfing everything down in a few frantic, sloppy minutes, while the other half are still setting the table and lighting candles.

Yes, we know:
mixed
strategies, lots of cheap sperm versus a few expensive eggs in one basket, and so on. But these flagrantly maladjusted sexual responses make far more sense when viewed as relics of our having evolved in promiscuous groups. Rather than spinning theories within theories in an effort to prop up an unstable paradigm—monogamy with
mistakes, mild
polygyny,
mixed
mating strategies,
serial
monogamy—can we simply face the one scenario where none of this self-contradicting, inconsistent special pleading is necessary?

Okay, fine, it’s embarrassing. Maybe even humiliating, if you’re prone to that sort of thing. But 150 years after
On the
Origin of Species
was published, isn’t it time to accept that our ancestors evolved along a sexual trajectory similar to that of our two highly social, very intelligent, closely related primate cousins? With any other question we have about the origins of human behavior, we look to chimps and bonobos for important clues: language, tool use, political alliances, war, reconciliation, altruism … but when it comes to sex, we prudishly turn away from these models to the distantly related, antisocial, low-I.Q.
but monogamous
gibbon? Really?

We’ve pointed out how the agricultural revolution triggered radical social reconfigurations from which we’re still reeling.

Perhaps the farfetched denial of our promiscuous sexual prehistory expresses a legitimate fear of social instability, but insistent demands for a stable social order (based, as we’re often reminded, upon the nuclear family unit) cannot erase the effects of the hundreds of thousands of years that came before our species settled into stable villages.

If female chimps and bonobos could talk, do we really think they’d be griping to their hairy girlfriends about prematurely ejaculating males who don’t bring flowers anymore?

Probably not, because as we’ve seen, when a female chimp or bonobo is in the mood, she’s likely to be the center of plenty of eager male attention. And the more attention she gets, the more she attracts, because as it turns out, our male primate cousins get turned on by the sight and sound of others of their species having sex. Imagine that.

“What

Horrid

Extravagancies

of

Minde!”

No man (who is but never so little versed in such matters) is
ignorant, what grievous symptomes, the Rising, Bearing down
and Perversion, and Convulsion of the Wombe do excite;
what horrid extravagancies of minde, what Phrensies,
Melancholy