For hundreds of years, we've been taught that sexual monogamy is natural for people. It’s the normal way. It’s the right way. Adulterers will be outcast and punished. Religious and cultural institutions have ingrained that men and women evolved in families in which a man's possessions and protection were exchanged for a woman's fertility and fidelity. But this monolithic and monogamistic worldview is now collapsing under its own weight.

And it isn’t even in the way out world of tantra and polyamory world that this is being felt – every year, fewer couples are getting married - out there, in mainstream society - and divorce rates keep skyrocketing. What results is a surge of single parents – which is suboptimal for childrearing, and couples who stay together but trapped in sexless, passionless unions of convention and despair. An entire industry has emerged to help people to somehow "rekindle the spark" without straying from the strict and severe confines of monogamy.

Sex at Dawn… the Dawn of Mankind

The rise and fall of traditional marriage is heralded in a new book, Sex at Dawn: The Prehistoric Origins of Modern Sexuality, written by Christopher Ryan and Cacilda Jethá, a psychologist and a psychiatrist who collaborated on this book. The authors use evidence gathered from human physiology, archaeology, primate biology and anthropological studies of pre-agricultural tribes from around the world, to argue that monogamy and the nuclear family are more recent inventions than most of us would expect — and far less natural than we've been taught to believe.

Their central contention is that human beings evolved in egalitarian groups that shared food, child care, and, often, sexual partners. Weaving together convergent, frequently overlooked evidence from anthropology, archaeology, primatology, anatomy, and psychosexuality, the authors show how far from human nature monogamy really is. Human beings everywhere and in every era have confronted the same familiar, intimate situations in surprisingly different ways. The authors expose the ancient roots of human sexuality while pointing toward a more optimistic future illuminated by our innate capacities for unconstrained love, cooperation, and generosity.

The book covers the themes of monogamy, sexual orientation, and family dynamics – through a deep exploration as to why long-term fidelity can be so difficult to maintain, why sexual passion tends to fade even when love deepens, why many middle-aged men risk everything for affairs with younger women, why homosexuality persists in the face of standard evolutionary logic, and what the human body reveals about the prehistoric origins of modern sexuality.

Here’s one example: when we think of the first swinger parties most of us imagine 1970s counter-culture, we don’t picture Top Gun fighter pilots in World War II. Yet, according to researchers, it actually was on military bases that “partner swapping” first originated in the United States. As the group with the highest casualty rate during the war, these elite pilots and their wives “shared each other as a kind of tribal bonding ritual” and had an unspoken agreement to care for one another if a woman’s husband didn’t make it back home. Like the bonobos, this kind of open sexuality served a social function that provided a way to relieve stress and form long-lasting bonds.

This example is one of many that suggests the human species did not evolve in monogamous, nuclear families but rather in small, intimate groups where “most mature individuals would have had several ongoing sexual relationships at any given time.” We are the descendants of these polyamorous and polyfidelitous mating groups and, even though we’ve constructed a radically different society from our hunter-gatherer forebears, the behavioral and psychological traits our species evolved in the distant past still reverberate in our behavior today.

The basic premise is that human beings are an exceedingly sexual species. As an example they detail how in 1902 the first home-use vibrator was patented and approved for domestic use in the United States. Fifteen years later there were more vibrators than toasters in American homes. In 2006, according to U.S. Pornography Industry Revenue Statistics, people around the world—the majority of whom were probably men—spent an estimated $97 billion on pornographic material, a figure that exceeded the annual revenue of Microsoft, Google, Amazon, eBay, Yahoo!, Apple, and Netflix combined. To judge human sexuality based on consumption patterns, as Stephen Colbert would say, “the market has spoken.”

Plus the authors explain that testicular size and the design of the penis strongly suggests that it evolved to create a vacuum in the female reproductive system, thereby pulling out the semen of anyone who was there previously. There are all kinds of indications of sperm competition in the human male. When this is combined with estimates that people engage in hundreds, and sometimes thousands, of copulations per child born (more than any primate, including chimpanzees and even bonobos) there’s little denying that the human animal is one sexy animal.

But why should a species often described as monogamous be so hypersexual? Monogamous animals by definition don’t have to compete for reproduction and, as a result, are generally characterized by a low level of sexual activity. But according to the authors, humans top a very short list of species that engage in sex for pleasure. “No animal spends more of its allotted time on Earth fussing over sex than Homo sapiens,” they write. In fact, the animal world is filled with species who confine their sexual behavior to just a few periods each year, the only times when conception is possible. Among apes the only monogamous species are the gibbons whose infrequent, reproduction-only copulations make them much better adherents of the Vatican’s guidelines than we humans are.

And so, the authors argue, repressing our sexuality should not be confused with reining in an “animal” nature… rather, it is denying one of the most unique aspects of what it means to be human.

Of course, none of what they write is exactly new. Psychologist David Barash and psychiatrist Judith Lipton detailed their own argument in The Myth of Monogamy (2001). And so, in Sex At Dawn, the authors cover some similar ground, but also provide a great deal of additional material that was unavailable a decade ago. Thus, the book is a provocative and engaging synthesis of the latest research on human sexual evolution that has the added benefit of being a joy to read. While the authors’ conclusion that healthy relationships can be both committed and open may come as a shock to some readers, others – especially those in the poly/tantra community - will likely find it refreshingly honest.

However, when asked if there’s a better model for relationships than monogamous marriage, the authors don’t really have an answer. In an interview, they stated, “We don’t even really know what to do with this information ourselves. What we’re trying to do in the book is give people a more accurate sense of where we came from, why we are the way we are, and why certain aspects of life feel like a bad fit. I think a lot of people make a commitment when they’re in love, which is a sort of a delusional state that lasts a couple of years at most. I think it was Goethe who said that love is an unreal thing, and marriage is a real thing, and any confusion of the real with the unreal always leads to disaster.