Are new dating apps killing monogamy - or has it always been dead?

Her first marriage, in her early 20s, had ended after an affair. (Hers.) Her second marriage, started shortly thereafter, was "happy — very happy," but as her boys grew up and moved out and moved on, she was left faintly bored.

She thought about cheating on her husband of 20 years. She considered bars, parties, a review of the lapses in her mid-20s.

Instead, she sat her husband down and told him something that more and more progressive couples are beginning to realize. They loved each other and wanted to stay together — but in the age of Tinder and Ashley Madison and OkCupid, they also both wanted to have other options. Options they knew were just a click away.

"Interesting, introspective, happily married D.C. professional," reads Jessie's profile on the new non-monogamous dating site Open Minded. "I'm into building deep and loving relationships that add to the joy and aliveness of being human."

Open Minded isn't quite like Ashley Madison, the unapologetic dating-for-cheaters service that expects a billion-dollar valuation when it launches its impending IPO. It also isn't quite like mobile hook-up app Tinder, where — according to one recent report — as many as 40 percent of "singles" are secretly ... not.

Instead, says Brandon Wade, the site's pragmatic, MIT-educated founder, Open Minded is a new kind of dating site for a newly mainstream lifestyle: one in which couples form very real attachments, just not exclusively with each other. He expects swingers, polysexuals and experimental 20-somethings to use his site. But he guesses that most of his 70,000 users are people like Jessie: Those in committed, conventional relationships, who realize that, statistically speaking, few modern couples stay with a single person their whole lives.

"If you look at marriage, it developed as a survival strategy and a means of raising kids," Wade said. "But relationships are no longer a necessary component of life. People have careers and other interests — they can survive without them."

That's not wrong, says Helen Fisher, a biological anthropologist and one of the world's leading relationship researchers. In the caveman days, humans teamed up in non-exclusive pairs to protect their children. Later, as people learned to plant crops and settle in one place, marriage became a way for men to guarantee kids, and for women — who couldn't push heavy plows or carry loads of crops to market — to eat and keep a roof over their heads.

There's a long history of married men sleeping around, Fisher said. And the romantic notion that relationships are anything but transactions is relatively recent — as is the social expectation that both people partner for life, to the exclusion of everyone else.

In fact, given the history and prevalence of non-monogamous relationships throughout cultures, it's not scientifically correct to say the human species mates or pairs for life. Dogs mate for life. Beavers mate for life. Humans have one-night stands, paramours and a 50 percent divorce rate.

Fisher dubs it a "dual reproductive strategy": We're biologically programmed to form pair-bonds, yes, but some people — many people — are also programmed to seek out variety.

Just consider the number of married men who have partners outside of their marriage — more than 40 percent in the United States. (That's down, by the way, from past decades.) Recent research suggests that the network of secondary partners we developed in our cavemen days is still around on Facebook, where we poke and message as many as eight could-be partners in anticipation of rainy days. Even Leviticus tacitly permitted male adultery, provided the act didn't involve a married lady.

"Nothing about this is new. It's as old as the hills," Fisher said. "What is new is that women are now also being more adulterous — and so people are beginning to be more open about it."

Jessie doesn't like that word. Adultery. It conjures images of lipstick stains and burner phones. Or worse, stonings and scarlet A's. It also reminds her of her first marriage, which ended after an affair. She hated the lying, the sneaking around. This time, she wanted to be more honest.

In 2010, Jessie approached her husband with an idea she called "ethical non-monogamy." They would stay together as each other's primary, lifelong partners, but they wouldn't rule out other relationships — as long as they happened openly. Jessie has shown her husband her profile on several dating sites, including Open Minded. When she returns from her weekly date with one of her four extramarital partners, she tells him as much, or as little, as he likes.

Publicly, no one knows about this arrangement. (It's why we have agreed to just use her first name in this story.) Jessie doesn't plan to tell her children, though she could see it coming up one day. She and her husband still have sex, still go to social functions, still celebrate anniversaries.

But that whole thing about "the woman which hath an husband is bound by the law ... so long as he liveth"? To that, Jessie says no thanks.

More and more women will make this choice or consider it, Fisher expects; it's in keeping with decades of widespread social change and women's empowerment. Just 30 years ago, when Jessie was in her 20s, the average woman married at 23 and had her first child within the year. Her mother's generation didn't even leave the home. The majority simply raised kids, preached chastity and finger-waved their hair.

"That's all sliding away from us," Fisher said. "We're shedding all these agricultural traditions ... (and) returning to the way we were millions of years ago."

Internal data from Open Minded would appear to back that up: Thus far, most of its self-declared "monogamish" users are under 33. In other words, they're women (and men) who paid off their own student loans, fooled around on Tinder — and grew up with a notion of personal independence much different from the one taught in the 1st century A.D.

For them, and for their more conventional peers, Jessie has some advice: Talk to your partner about monogamy. Listen "without judgment." Keep, in all cases, an open mind.