one reason you humans are "special"

SciAm | Now back to masturbation fantasies and cognition—and this is where it gets really interesting. Baker and Bellis’s theory may be peculiarly true for human beings, because from all appearances, under natural conditions, we are the only primate species that seems to have taken these seminal shedding benefits into its own lascivious hands. Unfortunately, there have been a paltry handful of studies tracking the masturbatory behaviors of nonhuman primates. Although some relevant data is probably buried in some mountain of field notes, I didn’t come across any targeted studies on the subject in wild chimpanzees , and even the prolific Jane Goodall doesn’t seem to have ever gone there. But nevertheless by all available accounts, and by contrast with human beings, masturbation to completion is an exceedingly rare phenomenon in other species with capable hands very much like our own. As anybody who has ever been to the zoo knows, there's no question that other primates play with their genitalia; the point is that these diddling episodes so seldom lead to an intentional orgasm.

So why don’t monkeys and apes masturbate even nearly as much as humans? It’s a rarity even among low status male nonhuman primates that frustratingly lack sexual access to females–in fact, the few observed incidents seem to be with dominant males. And why haven’t more researchers noticed such an obvious difference with potentially enormous significance for understanding the evolution of human sexuality? After all, it’s been nearly 60 years since Alfred Kinsey first reported that 92 percent of Americans were involved in masturbation leading to orgasm.

The answer for this cross-species difference, I’m convinced, lies in our uniquely evolved mental representational abilities—we alone have the power to conjure up at will erotic, orgasm-inducing scenes in our theater-like heads … internal, salacious fantasies completely disconnected from our immediate external realities. One early sex researcher, Wilhelm Stekel, described masturbation fantasies as a kind of trance or altered state of consciousness, “a sort of intoxication or ecstasy, during which the current moment disappears and the forbidden fantasy alone reigns supreme.”