This spring, on the eve of the equinox at a loft party in Brooklyn, I hinted to a woman I'd been crushing on that we might have a vibe. She was tomboyish with wavy mermaid hair; an engineer, a skater and punk guitarist. We were both surprised when she hopped into my Lyft and called in sick the next day, weathering a spring blizzard from my bed. It was not unlike spontaneous nights I'd had with men, but at 37, it was my first with a woman.

We’ve been together ever since.

My whole life, I dated and loved only men. But when I told family and friends I was dating a woman, no one seemed shocked — for some reason, that bothered me. I imagined them all in a room together, nodding solemnly and saying, "So this is why she never settled down.” Though I was raised by a free-spirited nomadic mother in a liberal environment surrounded by queer folks, I felt compelled to make it clear that I wasn’t coming out. This was situational. I had simply fallen in love with a person and that person happened to be a woman. That’s all there was to it.

Right?

While the more progressive part of me wasn’t concerned with what I called the relationship, another part of me needed to understand — to give a name to this sudden switch. During downtime at work, I started searching for an explanation. What I found was a surprising amount of research. Every doctor I subsequently spoke to had slightly different theories on the matter, but all of them agreed on one thing: late in life sexual fluidity in women actually isn’t all that uncommon.

Dr. Sheryl Kingsberg, a professor and division chief of behavioral medicine in the OB/GYN unit at University Hospitals Cleveland Medical Center, tells me that in her clinical work, she’s seen straight cis women like me experiencing sudden same-sex attraction. “I have seen a mild increase in my own practice of women in their 30s over the last decade,” says Kingsberg. They’d been happy with men all their lives. Maybe they’d married, many already had children. And at some point in their 30s or 40s, a switch just flipped.

Kingberg says it’s difficult to separate an increase in the phenomenon from an increase in social acceptance of queerness, but that there are biological underpinnings for some women. “Maybe it’s hormonal, maybe it’s neuroendocrine —an epigenetic shift in brain chemistry that is hormone-based. But it’s certainly a shift.”

Dr. Lisa Diamond, professor of developmental psychology at University of Utah, is one of the foremost researchers on sexual fluidity in women, which she believes is situational. According to Diamond, some women can desire women under certain circumstances regardless of their overall orientation.

“The question of whether such a woman is ‘fluid’ versus ‘bisexual’ is a complicated one,” says Diamond. “If a woman has only had one same-sex attraction or affair, and really feels that it was focused on that one specific person, that is more likely to be an instance of fluidity. One of the risks of the ‘repressed lesbian’ narrative is that it leads women to feel that their previous relationships with men must have been ‘fake’ or ‘inauthentic.’ It’s completely possible that a woman had a totally satisfying history of relationships with men, and is now experiencing totally new and equally satisfying relationships with women.”

Image zoom Emma Darvick

Dr. Christine Hyde, 48, a therapist at the New Jersey Center for Sex Therapy, has experienced this flavor of fluidity herself and treated a dozen clients with similar stories in the past 25 years. “The evolutionary perspective really does make sense,” she says. “All of my clients were in their late 30s, early 40s. All of them had children and all of them were done having children. There were big transitions that seemed to parallel the time in which this happened. It was a time when they began to individuate. It was a time when they switched careers. It was a time when they moved across the country.”

While learning the potential scientific and social roots of fluidity helped me understand it intellectually, I also needed to talk to someone who’d gone through this themselves.

Nashville singer-songwriter Katie Herzig, whose songs have been on Grey’s Anatomy and Big Little Lies, found herself wrestling with titles when she met and slowly fell for her current partner and fellow musician Butterfly Boucher, a love story first captured in nuance by the WNYC podcast, Nancy. At 33, Herzig had always dated men, and Boucher, at the time, was in an eight-year relationship with a man. They became fast friends after Herzig moved to Nashville, chatting online, texting at all hours, but Herzig was surprised when Boucher expressed romantic feelings. It was a journey from that profession to their life together today — Boucher steady along the way, Herzig working to reconcile her ideas of self with this new truth. She, like me, became defensive when people implied she might have always had it in her.

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“I almost felt guilty for pushing back on being gay. But I didn’t want the life I’d lived up to that point to be negated in any way,” she says. “When you say you’re with a woman people immediately have this backstory in their minds. Eventually, I had to make peace with the fact that people will assume what they want.”

Dr. Hyde was also met with confusion from her parents and friends when after 11 years in an open marriage, she experienced the same sexual flip she’d helped patients through. Pregnant with her second child, she found herself wishing Michelle, a friend of five years that she’d never seen in a sexual way, was in the delivery room instead of her husband. “Things were not in such bad shape that I wanted a divorce or anything like that.”

Yet, within two years of her child being born, she’d divorced her husband and married Michelle. Still, it took her almost three years to identify as lesbian — years during which she watched her once vigorous sexual attraction to men diminish. “I think it’s a whole sexual shift. Some of the best sex I ever had in my whole damn life was with guys, so it’s not like sex wasn’t great. I just don’t have any interest.”

I could definitely relate to that. After a lifetime of strong sexual attraction to men, I’d found myself losing interest as well. In the months after my girlfriend and I got together, even the hottest guy on the train sparked only an aesthetic appreciation. At first I’d been convinced it was just her, but I started to wonder if I’d ever go back to men. While I embraced fluidity in theory, it was hard to believe it could be permanent—could I truly remain sexually attracted to, satisfied, and in deep romantic love with women for the rest of my life?

In Kingsberg’s clinical experience, while some women reorient to men or non-binary folks, the majority who experience this sexual switch at 30 and older end up with women for the long haul. “The bonding between women goes beyond sexual attraction,” Kinsberg explained. “So that additional value may push it toward, ‘Why would I go back to men?’ Oxytocin [dubbed the love hormone] may be a contributing factor — that women have more oxytocin than men — towards their ability to fall in love with somebody and then develop attraction, which is why women are more likely to be fluid.”

An embrace of fluidity can be difficult to grasp, even for those living it. Herzig found the experience didn’t lead to a tidy re-assignment of the self, but an elliptical, often messy, unfolding.

“The part of me that grew up feeling straight still feels like there’s this unlived dream of being with a man,” says Herzig. “But when you let go of that, you’re opening up space for this totally other big thing, which is the energy of myself with another woman. I have developed this appreciation for an expansion of attraction.”

While who we are attracted to and love may not be a choice, sometimes the decision to pursue it can be a daunting one. In a time when trans folks are fighting for the right to live and thrive and LGBTQIA+ rights are being stripped with every news cycle, I wonder how stories like mine and the women and doctors I spoke with can help break down binary thinking.

“Ultimately, there are as many humans as there are different stories of how love comes together and is expressed,” says Herzig. “The world is still trying to catch up to this.”

I am still catching up too, learning to allow for love and attraction without confines. By 37, I was confident I knew everything there was to know about myself. Having something as fundamental as my sexuality shift, while at first unnerving, has ultimately left me excited to see what other surprises the future may hold.