Sex at Dawn полностью

Leaving aside for the moment the disturbingly Freudian notion that even Mother Nature is obsessed with the penis, our bodies certainly contain a wealth of information about the sexual behavior of our species over the millennia. There are clues encoded in skeletal remains millions of years old and pulsing in our own living bodies. It’s all right there—and here. Rather than closing our eyes and dreaming, let’s open them and learn to read the hieroglyphics of the sexual body.

We begin with body-size dimorphism. This technical-sounding term simply refers to the average difference in size between adult males and females in a given species. Among apes for example, male gorillas and orangutans average about twice the size of females, while male chimps, bonobos, and humans are from 10 to 20 percent bigger and heavier than females. Male and female gibbons are of equal stature.

Among mammals generally and particularly among primates, body-size dimorphism is correlated with male competition over mating.² In winner-take-all mating systems where males compete with each other over infrequent mating opportunities, the larger, stronger males tend to win . and take all. The biggest, baddest gorillas, for example, will pass genes for bigness and badness into the next generation, thus leading to ever bigger, badder male gorillas—until the increased size eventually runs into another factor limiting this growth.

On the other hand, in species with little struggle over females, there is less biological imperative for the males to evolve larger, stronger bodies, so they generally don’t. That’s why the sexually monogamous gibbons are virtually identical in size.

Looking at our modest body-size dimorphism, it’s a good bet that males haven’t been fighting much over females in the past few million years. As mentioned above, men’s bodies are from 10 to 20 percent bigger and heavier than women’s on average, a ratio that appears to have held steady for at least several million years.

Owen Lovejoy has long argued that this ratio is evidence of the ancient origins of monogamy. In an article he published in Science in 1981, Lovejoy argued that both the accelerated brain development of our ancestors and their use of tools resulted from an “already established hominid character system,” that featured “intensified parenting and social relationships, monogamous pair bonding, specialized sexual-reproductive behavior, and bipedality” Thus, Lovejoy argued, “The nuclear family and human sexual behavior may have their ultimate origin long before the dawn of the Pleistocene.” In fact, he concluded with a flourish, the “unique sexual and reproductive behavior of man may be the sine qua non of human origin.” Almost three decades later, Lovejoy is still pushing the same argument as this book goes to press. He argues—again in Science—that Ardipithecus ramidus’ fragmentary skeletal and dental remains dated to 4.4 million years ago reinforce this view of pair bonding as the defining human characteristic—predating, even, our uniquely large neocortex.¹

Like many theorists, Matt Ridley agrees with this ancient origin of monogamy, writing, “Long pair-bonds shackled each ape-man to its mate for much of its reproductive life.”

Four million years is an awful lot of monogamy. Shouldn’t these “shackles” be more comfortable by now?

Still, some continue to insist that humans are naturally polygynous harem-builders, despite the paucity of evidence supporting this argument. For example, Alan S. Miller and Satoshi Kanazawa claim that, “We know that humans have been polygynous throughout most of history because men are taller than women.” These authors go on to conclude that because “human males are 10 percent taller and 20 percent heavier than females, this suggests that, throughout history, humans have been mildly polygynous.”⁵

Their analysis ignores the fact that the cultural conditions necessary for some males to accumulate sufficient political power and wealth to support multiple wives and their children simply did not exist before agriculture. And males being moderately taller and heavier than females indicates reduced competition among males, but not necessarily “mild polygyny.” After all, those promiscuous cousins of ours, chimps and bonobos, reflect precisely the same range of male/female size difference while shamelessly enjoying uncounted sexual encounters with as many partners as they can drum up. No one claims the 10 to 20 percent body-size dimorphism seen in chimps and bonobos is evidence of “mild polygyny.” The assertion that the same physical evidence correlates to promiscuity in chimps and bonobos but indicates mild polygyny or monogamy in humans shows just how shaky the standard model really is.