Our unique brains result from our chatty sociability. Though debate rages concerning precisely why the human brain grew so quickly, most would agree with the anthropologist Terrence W. Deacon when he writes, “The human brain has been shaped by evolutionary processes that elaborated the capacities needed for language, and not just by a general demand for greater intelligence.”
In a classic feedback loop, our big brains both serve our need for complex, subtle communication and result from it. Language, in turn, enables our deepest, most human feature: the ability to form and maintain a flexible, multidimensional, adaptive social network. Before and beyond anything else, human beings are the most social of all creatures.
We have another quality that is especially human in addition to our disproportionately large brains and associated capacity for language. Perhaps unsurprisingly, it is also something woven into our all-important social fabric: our exaggerated sexuality.
No animal spends more of its allotted time on Earth fussing over sex than Homo sapiens—not even the famously libidinous bonobo. Although we and the bonobo both average well into the hundreds , if not thousands, of acts of intercourse per birth—way ahead of any other primate—their “acts” are far briefer than ours. Pair-bonded “monogamous” animals are almost always hyposexual, having sex as the Vatican recommends: infrequently, quietly, and for reproduction only. Human beings, regardless of religion, are at the other end of the libidinal spectrum: hypersexuality personified.
Human beings and bonobos use eroticism for pleasure, for solidifying friendship, and for cementing a deal (recall that historically, marriage is more akin to a corporate merger than a declaration of eternal love). For these two species (and apparently only these two species), nonreproductive sex is “natural,” a defining characteristic.
Does all of this frivolous sex make our species sound “animalistic”? It shouldn’t. The animal world is full of species that have sex only during widely spaced intervals when the female is ovulating. Only two species can do it week in and week out for nonreproductive reasons: one human, the other very human like. Sex for pleasure with various partners is therefore more “human” than animal. Strictly reproductive, once-in-a-blue-moon sex is more “animal” than human. In other words, an excessively horny monkey is acting “human,” while a man or woman uninterested in sex more than once or twice a year would be, strictly speaking, “acting like an animal.”
Sex at Dawn
Ryan and Jethá 2010