A startling number of Japanese youths have turned their backs on sex and relationships, a new survey has found.

The survey, conducted by the Japan Family Planning Association, found that 36% of males aged 16 to 19 said that they had “no interest” in or even “despised” sex. That’s almost a 19% increase since the survey was last conducted in 2008.

If that’s not bad enough, The Wall Street Journal reports that a whopping 59% of female respondents aged 16 to 19 said they were uninterested in or averse to sex, a near 12% increase since 2008.

The survey paints a bleak picture for Japan’s aging population. The Associated Press reports that the national population of 128 million will have shrunk by one-third by 2060 and seniors will account for 40 percent of people, placing a greater burden on the work force population to support the country’s social security and tax systems.

Many commentators in the Japanese and international media have laid the problem squarely at the feet of soshoku danshi — “herbivore men” — a term coined by pop culture columnist Maki Fukasawa in 2006. It refers to Japanese young men who have rejected their culture’s traditional definition of masculinity, and seemingly eschew relationships with the opposite sex as part.

CNN spoke to a Midori Saida, a 24-year-old Japanese woman who described “herbivore men” as “flaky and weak.”

“We like manly men,” she said. “We are not interested in those boys — at all.”

BBC News spoke to one such “herbivore” man (see video). The man, Yusaki Yakahashi said: “Building a relationship seems like too much effort. To get her to like me and for me to like her… I’d have to give up everything I do at the weekend for her. I don’t want to do that.”

Another theory that seeks to explain Japan’s shrinking population is that Japanese youth spend too much time engaged with technology, living in virtual worlds or settling for virtual girlfriends rather than real ones.

Britain’s Daily Telegraph reports that Japan’s government has undertaken a series of campaigns to encourage couples to have more children — including making companies insist that their staff leave work at 6 pm to increase child allowances — but according to Dr. Kunio Kitamura, head of the Japan Family Planning Association, “none of that is gong to have an impact if people are not going to have sex.”

Sixty years ago, Alfred Kinsey, a professor of zoology at Indiana University, published Sexual Behavior in the Human Male, an 804-page tract documenting impressively high rates of non-normative behavior among ordinary Americans, including widespread premarital intercourse, marital infidelity, homosexuality, and masturbation. The report made a ponderous pretense at being value-free.

The scientific facade fooled no one. Despite Kinsey’s numerous assertions that he was merely an empiricist, the disclaimers were disingenuous. A polemicist with a strongly sex-affirmative and antiguilt agenda, he was intent upon proving that many if not most American men deviated significantly from the social rules governing sexual behavior, and that had their transgressions been discovered, quite a few of them would have been found guilty of breaking a law. Kinsey’s take-home message outraged the defenders of bourgeois rectitude, whose hysterical indignation was contemporary with the intensification of the Cold War, the rise of aggressive McCarthyism, and the escalated emphasis on conservative family values and gender roles. Five years later, it was no surprise when the publication of Kinsey’s companion volume Sexual Behavior in the Human Female (asserting, among other things, that a woman’s capacities for orgasm and marital infidelity were essentially no different from a man’s) was met with a storm of objection in the media that successfully laid waste to the zoologist’s credibility and funding.

If in America the Kinsey Reports sold into the markets for prudery as well as prurience (the voyeuristic fascination inseparable from the moral outrage), the European response—especially among West German, French, and Swiss journalists, sociologists, and theologians—is less well known. It was also one of horror—not at the prevalence of sexual activity, but rather at what was perceived to be an utter lack of genuine sensuality in American culture. As a Swiss psychoanalyst put it in his critique of the Kinsey Reports, “Everything exudes an air of numbed lovelessness.”

European commentators were aghast. In erotic terms, the United States was a frightful wasteland: the women were apparently frigid, the men sexually inept. The American “dating game” was said to epitomize a culture of rampant competitiveness and superficiality. Single females needed to enhance and falsify their breast size to achieve any sexual self-esteem at all, and married women found their only fulfillment in the success of their husbands’ business careers. To European eyes, the version of Protestantism that dominated the American scene instilled sexual inhibition in men and women alike; the distinctly American premarital activity known as “petting” was seen not as a clever compromise that permitted mutual orgasm without the risk of pregnancy but as yet another sign of the sex-negativity of American culture. With a zeal that can only be read as schadenfreude, Europeans described the chief military and ideological victors of World War II as pathetically lacking in erotic imagination and playfulness. Above all, they emphasized that there was something sad (as opposed to threatening) in the world Kinsey envisioned.

Europeans fixed on something that many Americans had not. Kinsey counted orgasms the way other people counted beans or pennies or cars on the highway: he considered orgasms (or “sexual outlets” as he called them) equivalent units that could be added, subtracted, and compared. The problem with Kinsey, his Europeans critics contended, was that he never thought about the quality of the orgasm, only its quantity. And he never thought at all about love.

In 1955, the French journal Esprit accused Kinsey of deromanticizing sex with his mindless fixation on “outlet” statistics and his “rudimentary” understanding of sexual passion. What Kinsey seemed unable to imagine, the French critics argued, was that emotions mattered just as much as, if not more than, the “machine-like” manipulation of another person’s genitals. “The desire to know the other, the vertigo of curiosity” about one’s partner: that was the decisive ingredient at the moment of orgasm that defined great lovemaking. Rather than finding genuine communion and “something precious to exchange,” the “human animals” that Kinsey described could seek at best a “spasm of consolation.” “Lacking all love, all tenderness,” there was nothing but the contact between skin and skin, between “autonomous nerves.” This, Esprit concluded, was truly solitude à deux: deep loneliness in the midst of sexual activity. When Americans had sex with each other, they were really just having sex with themselves.

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 Joan and Dwight Dixon, it 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 sexy apes known as bonobos, this kind of open sexuality served a social function that provided a way to relieve stress and form long-lasting bonds.

For the husband and wife team Christopher Ryan and Cacilda Jethá in their new book Sex At Dawn, 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 multimale-multifemale 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 manifest themselves today. Ryan, a psychologist, and Jethá, a psychiatrist, argue that understanding human sexual evolution this way helps to explain our species’ unique creativity inside (as well as outside) the marriage bed. It may also shed light on why fidelity has been such a persistent problem for both men and women throughout recorded history.

For Ryan and Jethá there is little doubt 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 (today this number could be as high as fifty million nationwide). 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 ($13.3 billion in the U.S. alone), 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.” 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 bonobos) there’s little denying that the human animal is one sexy beast.

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 Ryan and Jethá 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 are. In this way, Ryan and Jethá 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.

The suggestion that humans did not evolve as a monogamous species is not as radical an idea as it may sound. In The Descent of Man Charles Darwin wrote, “Those who have most closely studied the subject [particularly the anthropologist Lewis Henry Morgan] believe that communal marriage was the original and universal form throughout the world.” Yet ever since the nineteenth century anthropologists have struggled over how to identify the mating system of human beings. In 1967 George P. Murdock’s Ethnographic Atlas reported that only 14.5% of modern preindustrial societies could be classified as monogamous. Yet, in the West, researchers commonly refer to humans as “serially monogamous,” based on the pattern of repeated monogamous marriages throughout men and women’s lifetimes. But with over half of divorces occurring because of infidelity and one in 25 dads unknowingly raising children that they didn’t father, this is not a picture that fits comfortably with monogamy of any sort, serial or otherwise.

However, by looking at modern indigenous societies and comparing the findings of anthropologists with the latest results in behavioral psychology and biology, Ryan and Jethá piece together a remarkably coherent pattern from an otherwise fractured understanding of human sexuality. From societies that believe that multiple men are necessary for a successful pregnancy (what researchers refer to as “partible paternity”) to those where not having an extra-marital tryst will cause a man to be labeled “stingy of one’s genitals” by his female suitors, the authors conclude that marriage may be an established social arrangement among many hunter-gatherers but it’s one in which sexuality is decidedly fluid. A range of physiological evidence from Western populations is further offered to support this position, from the year-round libido in both sexes, to the unusually large size of men’s genitalia compared to other apes, to the shifting sexual strategy during various stages in women’s reproductive cycle (and lest we forget multiple female orgasms?). All suggest that our species is adapted for several concurrent sexual partners.

This is, of course, not a new idea in human evolutionary research. Primatologist Sarah Hrdy advocated a promiscuous mating system for humans in The Woman That Never Evolved (1999) while psychologist David Barash and psychiatrist Judith Lipton detailed their own argument in The Myth of Monogamy (2001). In Sex At Dawn Ryan and Jethá cover some similar ground as these previous authors but provide a great deal of additional material that was unavailable a decade ago. They also emphasize the ways in which monogamy has been used as a means of controlling women in patriarchal societies and make a number of insightful connections between the invention of agriculture 12,000 years ago and how sedentary societies influence the structure of human mating. However, with a relaxed writing style and numerous examples from modern popular culture, their discussion of these topics remains readily accessible even to those who may be encountering such ideas for the first time.

Sex At Dawn 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 will likely find it refreshingly honest. As their example of WWII fighter pilots emphasizes, human sexuality has numerous social as well as emotional functions and there has never been only a single path chosen by the human species. In offering a fresh look at a fascinating and controversial topic Sex At Dawn is a book sure to generate discussion, and one likely to produce more than a few difficult conversations with family marriage counselors.

Naughty Schoolgirl and Teacher who is frustrated because of the budget cuts and the increasing pressure to teach toward standardized tests.

Strict Babysitter and Misbehaving Child who is acting out because he is being used as a pawn of manipulation for his emotionally dysfunctional and divorced parents.

Bored Housewife and Meter Reader who is in danger of losing his job because of the collapse of the economy and his corrupt worker’s union will likely let his benefits lapse.

Wealthy Homeowner and Naughty French Maid who is eager to comply with all requests because she is living in fear that she and her family could be deported at any time.

Naughty Prostitute and Police Officer who is annoyed at all the paperwork he has to do for this arrest especially since his shift is almost over and he’s already worked a sixty-hour workweek.

Naughty Secretary and Powerful CEO who is questioning his life choices and his participation in socioeconomic oppression after walking past the Occupy Wall Street camps evey morning as he comes into work.

Big Time Film Director and Innocent Ingenue who is trying to be cast in his movie because if this is not her big break then her parents will stop paying her rent in her studio apartment in Burbank and demand that she move back home with them in Ohio and get a job at Burger King to help pay the rent.

Bored Man and Bored Woman trying to add some spice to their sex life.