LONG BEACH, CA—Thursday afternoon at the TED2013 conference got a little steamy. Christopher Ryan, a PhD of psychology and co-author of the book Sex at Dawn, sexed up the stage by talking about what he believes is the evolutionary nature of human sexuality. “Human beings are not descended from apes," he told the crowd. "We are apes. We’re [genetically] more closely related to chimps and bonobos than they are to any other primate.” As Ryan puts it, the question is “what kind of ape are we” in terms of our sexual natures? It turns out that we’re also closely related to chimps and bonobos in sexual practices—and the latter are famous for their sexual promiscuity and even “homosexuality.”

Consider that the average human has sex about 1,000 times per birth. According to Ryan, we share that number of sexual encounters with chimps and bonobos, but other primates are vastly different. Gorillas and all other primates typically have sex only 12 times per birth.

And, Ryan added, the frequency of sexual engagement is one reason humans, chimps, and bonobos have larger external testicles. Humorously comparing testicles to a beer fridge, Ryan noted that the idea is to be ready for a big party at any moment, with plenty to share. In other words, external testicles are all about frequent and spontaneous ejaculation.

What does this mean for human sexuality? Ryan argued that human sexuality evolved to function first and foremost as a bonding function, with reproduction being secondary (note this is sexuality, and not sex itself). This would mean that humans are indeed very similar to chimps and bonobos, which use sex for social purposes. Bonobos take socially driven sex to an extreme, in both hetero- and homosexual ways.

Ryan noted that the standard narrative of human sexuality is that men have bargained for women’s sexual functions by being providers/hunters, and women have complied as a result of this benefaction and protection. But the problem with this narrative, he suggested, is that the origin of human civilization doesn’t support this model. Before the advent of agriculture, we lived in hunter/gatherer societies that were fiercely egalitarian. Everything was shared.

Wouldn’t that include sexual relationships? Ryan says yes. Sexual exclusivity came later, after the advent of agriculture and more complex notions of property and exclusivity arose. But this development doesn’t change our nature. “Just because you have chosen to be a vegetarian,” he jokes, “doesn’t mean that bacon stops smelling good.” Just because we live in societies that generally organize around monogamous principles does not mean monogamy is the natural state of human sexuality. Like chimps and bonobos, it is natural for humans to have sexual desires for bonding.

In the end, Ryan argues that we must cease to conflate desires with property rights. We need to move beyond "men are from Mars and women are from Venus," he proclaimed to much applause. "The truth is that men are from Africa and women are from Africa.”