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.Ryan argues that his book should be very upsetting to social conservatives, because he shows that there is no such thing as traditional marriage. Some anthropologists have claimed that marriage is universal, but only by broadening the definition of marriage to include just about all sexual relationship.
Ryan argues that primitive hunter-gatherer societies had no need for marriage. There were no individual dependencies, no property rights, no reason for jealousy, and no child knew who his father was. Girls were free and sexually liberated like the ones famously (and inaccurately) described in Margaret Mead's Coming of Age in Somoa. He says countries like Sweden have moved closer to this sexual utopia by adopting socialist policies, and as a result Swedes have more relaxed ideas about monogamy and promiscuity. In the USA, you can find these jealously-free attitudes at a Las Vegas swingers convention.
Okay, maybe the Las Vegas swingers are trying to replicate the sexual promiscuity of a prehistoric hunter-gatherer tribe. How does that undermine what social conservatives say about traditional marriage?
Traditional marriage is not an attempt to mimic cave man behavior. If it were, then we would not need any marriage laws. Marriage is an invention of religion and law that made modern civilization possible.
When social conservatives advocate for laws protecting marriage, they are not doing it because they think that marriage instincts are innate. They do it because the institution of marriage depends on reinforcement from social norms, laws, and customs. And modern civilization depends on the marriage and family units. If it is true that we would all bahave like bonobos without marriage traditions, then that is all the more reason to protect those marriage traditions.