Many couples are finding meaning in loving, open relationships.
The Ravenhearts, a polyamorist couple, defined polyamory for the Oxford English Dictionary as "the practice, state or ability of having more than one sexual loving relationship at the same time, with the full knowledge and consent of all partners involved".
On a recent visit to a well-established centre of polyamory – Berkeley, California – I was instructed in the norms and bylaws by a long-term polyamorist who is clearly convinced it's the way to go: "It's perpetual harmony between the sexes, man, amazing sex in an atmosphere completely lacking in the negative and destructive emotions."
"Sixties free love in disguise?" I suggest. My adviser disagrees vehemently. "Polyamory is nothing like free love. It's about honest communication with good, loving intentions; it's about eroticism in all its forms; it's about inclusivity."
"No swinging at all?" I ask.
He frowns. "Swinging is just expenditure of energy, man. No love there, just raw physicality – like let's do it, then move on and do it again, maybe with two or three others."
He tells me he has been poly for years and that polyamorists "connect and communicate. We value the integrity of our connection".
Ryam Nearing of the organisation Loving More agrees. He says polyamory is about powerful sexual and emotional relationships.
I ask my expert about married people. Married is fine – if the partner agrees to participate, or agrees but refuses to participate.
"I used to be possessive about my girlfriend until I found out that her polyamory didn't turn me off; rather the reverse. And the more I thought about it the more I wanted some of her genuine cool about loving other people as well as me. It took a while but it worked for me."
I ask whether they're still together (they're not) and whether she is still polyamorous. He shakes his head. Apparently she wanted something different when she had a kid.
Is the child his? He shrugs. "I don't think so. She doesn't know for sure who the father is. Which is fine too; for a while I contributed financially, as did the others."
The Jim Evans poly pride flag consists of three equal horizontal stripes, with a symbol in the centre. Blue is for honesty, red for passion and black for solidarity with those who must conceal their relationships because of social pressures.
Most of mainstream established religions do not accept polyamory. But recently a prominent New York rabbi, Sharon Kleinbaum, said that biblical patriarchs had many wives and concubines, and there is no reason for the practice not to work today.
In 1929, Marriage and Morals by Bertrand Russell questioned Victorian notions of morality regarding sex and marriage; his views prompted vigorous condemnation. Virginia Woolf, DH Lawrence and others provoked a similar reaction.
Back in Berkeley I'm told that, although polyamorists have to be comfortable with whatever arrangements are negotiated – such as a husband with his wife's involvement with another woman, or her of his with another man – as important as good sex is the emotional support, the range of experience, skills and fresh perspectives of partners. Sharing child-rearing, chores and the reduced financial burden are powerful incentives.
Twice-weekly free-flow dances are held. I spoke to a woman who described the sensual appeal of these dances and the kind of opportunities they offer polyamorists. She has had a succession of experiences with attractive men who made rapid, romantic connections with her. Later, these men told her they practised polyamory and hoped she would become part of their group.
She no longer attends the dances because she can't imagine the complications that may arise. Investing in one relationship at a time is challenge enough for her. "So many guys are hopeless at emotional bonding," she says wistfully. "Those guys connected in an amazing way, and it was with me. It's just that they connect with others in the same way."
A manual for psychotherapists was published in 2009, titled What Psychotherapists Should Know about Polyamory.
A psychotherapist I spoke to says emotions such as jealousy and possessiveness can destroy even long-term partnerships.
A South African polyamorist (Jo'burg has an active polyamorist community) agrees. "It can take years to negotiate the intrusion of negative emotions," he says. "Some can't do it. The green-eyed monster is a powerful part of our psyches. It is not easily eradicated."
Rosemund Handler's latest novel, Us and Them, is published by Penguin