When I turned 30, in 2011, I envisioned my sexual experience eventually reaching a terminus, like a monorail gliding to a stop. I would disembark, find myself face-to-face with another human being, and there we would remain in our permanent station in life: the future.

I was single and straight. I had not chosen to be single, but love is rare and frequently unreciprocated. Without love, I saw no reason to form a permanent attachment to any particular place. My friends expressed a religious belief that it would arrive for me one day, as if love were something the universe owed to each of us, which no human could escape.

I had known love but, having known it, I knew how powerless I was to instigate it or ensure its duration. I knew that it did not arrive for everyone, and as I got older I began to worry it would not arrive for me.

On a Monday in April 2012, I stood in line at JFK airport to board a plane to California. I had decided to visit San Francisco because my desires and my reality had diverged beyond the point of reconciliation. I wanted to picture a different future, one aligned with the freedom of my present, and in those years San Francisco was where the future was going to be figured out, or at least it was the city designated for people who still believed in free love. They gave their choices names and they conceived of their actions as social movements. They saw in new technology an opportunity to refashion society, including ideas about sexuality.

By 2012, the young people who came to San Francisco were neither dropouts nor misfits. They were children who had grown up eating sugar-free cereal, swaddled in polar fleece jackets made from recycled plastic bottles. They had studied abroad, knew their favourite kinds of sashimi and were friends with their parents. Unlike their parents, they commuted to the suburbs and lived in the cities. As they arrived, the cities reshaped to receive their disposable income.

In San Francisco, the young people went to coffee shops where the production of espresso was ritualised to resemble a historic re-enactment of the hardships of 19th-century pioneer life. Nobody smoked cigarettes. They honed their bodies with the aim of either perfect homeostasis or eternal life. They ate red meat only once a month, to time their consumption of iron with the end of their menstrual cycles. They started companies whose names referenced fantasy fiction. They were adults, but they could seem like children. Their sex lives were impossible to fathom, because they seemed never to have lived in darkness. They had grown up observing foreign wars, economic inequality and ecological catastrophe, crises that they earnestly discussed on their digital feeds, but avoided internalising as despair.

Soon Elizabeth had two non-boyfriends. Neither relationship had the expectation of exclusivity

I’m not saying Elizabeth was all of these things, but she described herself as an optimist. Elizabeth had a membership at a rock-climbing gym; she meditated and practised yoga. She organised hot-air balloon rides and weekend trips. She worked long, punishing hours, but had the energy to stay up all night at weekends, go on cycling excursions or attend silent retreats. A friend of mine had met her at a circus arts class and suggested I meet her.

Elizabeth had moved to San Francisco after college. Her boyfriend had moved to the south to go to medical school. No matter how much she loved him, or how much her mother, an infertility specialist, urged her to have children as a young woman, she was not yet ready to start a family. She had a job offer as a consultant at an economics firm. So, in 2010, when she was 22, she moved west and they broke up.

Elizabeth had never before lived in a city. She knew the suburbs in Virginia where she had grown up, and the small New England town where she had attended college. She arrived in San Francisco and made friends, some through internet dating.

She met Wes one night in late 2010, when he accompanied one of her co-workers to a boardgame party at her house. For their first date, they attended Nerd Night at a local bar. They watched a lecture about the future of teledildonics. On the walk home, they kissed. Then Wes, with the transparency he thought of as mature and fair, gave a speech of pre-emptive relationship indemnity. He was still getting over his last girlfriend, he said. He did not want to be in a relationship. Elizabeth tried not to roll her eyes – it was the first date! They said goodnight and parted ways.

Wes had grown up in San Francisco, studied computer science at Harvard and returned west after graduation to work at Google. Somewhere along the upward incline of his precocious youth, he had skipped a grade and was still only 21, tall and handsome.

Wes’s previous serious relationship, the one before he met Elizabeth, had ended during his senior year of college. At the time he met Elizabeth, the discovery of how much he liked casual sex was still new to him.

Still, Elizabeth and Wes lived near each other. They began meeting once a week for drinks, dates and sleeping over, always with a show of nonchalance. Given the choice, Elizabeth would have wanted a more serious commitment. She was only 23, but she had one reaction to Wes’s lack of interest in their relationship: he was acting like a baby. Fine, she decided. She would also see other people.

A few weeks later, she met Brian, a graduate of Stanford who also worked in tech. Soon Elizabeth had two non-boyfriends. Neither relationship had the expectation of exclusivity, or any defined path into the future. She kept the two separate and never saw the men together. They balanced each other, one providing security against the possible failure of the other.

One day in May 2011, six months after they met, Elizabeth introduced Wes to psilocybin mushrooms. The trip shifted their relationship. They still did not use the word “love”, but they now acknowledged what they referred to as “emotional involvement”.

Elizabeth was hired at Google. They took the bus to its Mountain View complex and ate in the cafeteria together. When they went for dinner with Wes’s family, Elizabeth was presented as a friend.

Elizabeth did not describe what she was doing – having sex with two men on a regular basis over an extended period of time, with the occasional extra-relationship dalliance besides – as polyamory. The word had cultural connotations for her, of swinging married people or creepy old men.

Although, like most people her age, she had friends whose partnerships allowed for sex with others, those friends tended to use the term “open relationship”, which was somehow less infused with the stigma of intentional weirdness, and did not amount to a proclamation of sexual identity.

Still, whatever accidental arrangement she had created, by the end of that year the lack of sexual boundaries was causing Elizabeth no small amount of anxiety. Wes’s crushes from high school were resurfacing. Women on the OkCupid dating site were probably sending him winky emoticons. To allay her growing insecurity, she turned to self-help and read The Ethical Slut: A Practical Guide To Polyamory, Open Relationships & Other Adventures, Sex At Dawn, by Christopher Ryan and Cacilda Jethá, and Tristan Taormino’s Opening Up.

These books convinced Elizabeth that monogamy was a choice, not a given. It began to take on the cast of an unreasonable expectation, best suited to people who disliked experimentation: people not like her.

Elizabeth compiled a shared Google doc – a syllabus of recommended reading, discussion groups and sex parties

For almost a year, Elizabeth and Wes avoided naming the terms of their relationship. They celebrated the last night of 2011 with friends, and before midnight, because she wanted to say it while still relatively sober, Elizabeth told Wes she loved him. He loved her, too, but he still wanted sexual freedom. She had already decided she wanted it, too.

They agreed that they would think of themselves as a couple from now on, instead of two single people who slept together, but they would still not be monogamous. Now they had to figure out how to manage the logistics. Elizabeth compiled a shared Google doc that was to become the foundation of their research – a syllabus of recommended reading, places to attend discussion groups and sex parties open to the public. They went to a party at a sex club and had sex surrounded by onlookers. They returned another night, for an open-relationship discussion group, but most of the attendees were in their late 30s and were either married and “frisky” or desperate to save their failing marriages.

Elizabeth and Wes felt they could draw upon certain ideas of the older polyamorists, but had to do a lot of the thinking on their own. After their research, they began to draw up rules.

The first held that, on any given night, one could call the other and say, “Will you please come home?” There was a shared understanding that each of them was the most important person in the other’s life. The second rule was about disclosure: if one of them suspected he or she might sleep with another person, the premonition should be disclosed. They agreed to discuss each other’s crushes. If a sexual encounter happened spontaneously, the event should be disclosed soon afterwards. They would use condoms with their other partners.

Despite making rules, they would aim to fail. It was a concept they borrowed from computer security: if an unplanned event occurs, the default is to act first, then worry about formulating responses for the next time.

Early in 2012, Brian left the country for three months. In the absence of her second partner, Elizabeth felt an imbalance. Wes was still dating other people and she felt vulnerable. She was also coming to terms with what had been a growing crush on someone else. His name was Chris. He happened to be Wes’s best friend.

Wes said he wouldn’t mind if Elizabeth and Chris started to sleep together. Elizabeth, upset, asked how he could possibly care about her and want her to sleep with his best friend. They worked it out.

Chris is a tall man with a sweet smile and a shy affect. His parents had met at a commune in Santa Barbara in the early 1980s, so the example he had was one of youthful adventure that would eventually settle into conformity. He met Wes at Google, where they both started working in 2010.

The two men were affectionate with each other, but Chris was surprisingly troubled by his unreturned desire for Wes

Chris and Wes became friends around the time Wes met Elizabeth. Compared with them, Chris had a more introspective personality. He was more careful about taking risks when it came to things such as drugs and relationships.

By the end of 2011, the three regularly socialised as a group outside work. Soon after, Chris and Elizabeth would also hang out by themselves. Chris knew that his new friends were in an open relationship, but at first he saw his own role as a mutual confidant, with a much closer relationship to his male counterpart.

One night, Chris accompanied Elizabeth and Wes to a queer dance party. They all danced together, dancing that evolved seamlessly to kissing on the dance floor. Chris enjoyed it, but felt a little bit like the third wheel. His friends were on MDMA and he was not. Elizabeth and Wes had planned a foursome with another couple later that night, so Chris ended up going home alone.

It became an unspoken understanding that if the three of them went out dancing, they would probably end up kissing together. This was true for a whole group of friends who began to coalesce at this time around Wes and Elizabeth, who began to be sought after as gurus by other couples who had considered opening their relationships. The shared Google doc soon had multiple subscribers.

Chris asked Wes whether he really did not mind if he and Elizabeth occasionally slept together. Wes said he didn’t. Then Chris brought up another idea: what about the three of them together, he asked carefully. Or just the two men?

Chris described himself as “mostly straight but every once in a while…” Wes happened to be one of the men to whom Chris was attracted. Wes, meanwhile, suspected that he was not at all gay, although in the spirit of the times he was having trouble making such a closed-minded declaration. He told Chris he needed to think about it.

The two men were affectionate with each other, even kissing hello or goodbye, but Chris was surprisingly troubled by his unreturned desire for Wes.

Emily Witt: ‘When it came to sex, I thought we had it much better than previous generations.’ Photograph: Michael Danner/The Guardian

I first met Chris, Elizabeth, and Wes in late May 2012, when their experiment was just a few months old. I was seven years older than Elizabeth and Chris, eight older than Wes. I envied the openness with which they shared their attractions. They did not proceed recklessly. They drew up ethical codes to protect their relationships. Elizabeth and Wes seemed to plunge forward through life without fear. I saw in Chris a little more hesitation.

They were not bothered, as I was, by the evidence that nonmonogamous arrangements had been rejected by the last generation of straight people who had tried them. I looked at the experiments of the 60s and 70s, and felt they had taught us that communes and other alternative arrangements that celebrated sexual freedom generally ended in jealousy and hurt feelings. We obedient children of the 80s and 90s saw the failures of the counterculture, and held ourselves in thrall to drug laws, health insurance, student loan payments, internships, condoms, skin protection factors, antidepressants, designated smoking areas, politically correct language, child safety locks, gym memberships, cancer screenings and career advancement. We had a nuanced understanding of risk.

When it came to sex, I thought we had it much better than previous generations. We knew better than to move into rural communes or force one’s wife to sleep with another man to overcome her cultural programming. We had more access to birth control, and knew more about our bodies. We had a vast selection of vibrators sold in woman-friendly retail environments. We had rape crisis centres, legal abortion and over-the-counter emergency contraception.

What my married parents imparted as the lessons from the 60s was that it was fine to have as much casual (“safe”) sex as we wanted as late-stage teenagers and young adults, and fine secretly to “experiment” with the more benign and least addictive drugs (although no teacher or relative ever openly recommended it), but eventually we would grow up and settle into the nuclear families we saw on television. Some of us would be gay and that would be fine. Many of these families would fall apart, but we did not consider divorce a structural failure of an institution, but a set of personal problems.

Among my mostly secular group of friends, the ceremonies of marriage and death were the only ritual sacraments left. I believed in the mystique of commitment. Could I think of myself as an adult if I never married? Would my married friends become distant and remote? Elizabeth, Wes and Chris believed there were still primary choices to make about sexuality. I wasn’t the only one who kept thinking about the warnings of people who had observed the 60s and felt hesitation. There was a phrase being thrown around the Bay Area only half-jokingly: “responsible hedonism”.

In the spring of 2012, Elizabeth would spend most nights with Wes and the occasional night with Chris or someone else. The three friends would see each other at work, too. When their relationships evolved, the shifts tended to happen not in slow increments, but with sudden tectonic upheavals, usually during out-of-town retreats that served as emotional crucibles.

Wes and Elizabeth’s relationship had acquired an acceleration, a momentum based on mutual daring. In the way that some couples might spend their energy systematically eating at new restaurants, Elizabeth and Wes went to sex parties. Elizabeth attended two porn shoots, one of them with Wes, the other with a woman who had become another long-term sexual partner. In June 2013, Wes left Google to start his own company. Between ending one job and beginning the other, he travelled around Europe. Elizabeth met him in Amsterdam, where they hired a prostitute.

In May 2013, Elizabeth took a work trip to Tokyo. Chris decided to go with her and play “house husband”. For the first time, they honestly discussed Chris’s understanding of Wes, of how, in Chris’s hopes and expectations, he had fallen in love – “filled in the dots with his own lines”, as Elizabeth put it. She left the conversation feeling they finally understood their differences, but also felt Chris’s romantic attraction to her break.

As untraditional as Wes and Elizabeth’s relationship was, it had started to look as if it was heading toward the traditional happy ending. They discussed moving in together, and finally did so in late 2013. The decision carried less weight with the knowledge that, at least a few times a month, one of them would be spending the night at someone else’s place. The lingering question for both was what would happen should one of them fall in love with someone else. They even discussed this likelihood with an older married couple, a couple in their late 30s who had been married for years. The man told them a story of how in the course of their open marriage, his wife had truly fallen for another person. He called it a “crisis episode”. They decided together that they were what they called “life journey partners” – a designation that sounded very hokey, but that was meant to indicate, Wes said, that “there’s being in love, and there’s being in love and wanting to spend the rest of your life with someone”. There would be times when a person had to compromise.

Party rules: 1. Low expectations, high possibilities. 2 Consent is required. 3 Parties are fun!

In August 2014, Elizabeth and Wes got engaged at the Burning Man festival. In August 2015, I attended their wedding in Black Rock City. To the tune of Somewhere Over The Rainbow played on an electric piano, Wes and Elizabeth, he in a white, button-down shirt and black trousers, she in a white dress, both with colourful face paint around their eyes, processed to an altar decorated with pink fabric flowers and tasselled fringe. Relatives delivered loving statements. Wes’s godfather recited a Druid prayer. We lit sparklers and held them skyward as the sun set, forming a ring of light. The drone of a didgeridoo obscured the couple’s quiet murmuring.

“By the power invested in me by the internet, you are now married,” said the officiant, Wes’s uncle. “You can kiss each other and other people.”

Chris and Elizabeth threw their first sex party in the fall of 2012. In early 2015, I went to the fourth iteration, Thunderwear IV, in a rented loft. A black-and-white portrait of Elizabeth lifting one of her legs up over her head in a full split and penetrating herself with a dildo hung over the room. She had installed a stripper pole.

The invitation had laid out the party’s rules in a charter, to which every invitee had to agree:

1 Useful mantra: low expectations, high possibilities.

2 Consent is required. And sexy. If you wanna do something, ask first. Bonus points for enthusiastic consent.

3 This is a party. Parties are fun! You don’t have to do anything you don’t wanna do. If you don’t wanna, say “no thanks”.

4 This is a party. Have fun! White ribbon means: ask to feed me (remember, you can say no). Red ribbon means: ask me for a kiss (on the cheek… at first, at least).

5 Relationship conversation with your partner recommended before you start partying.

There was one final rule: no glitter, at the request of the venue.

The party started calmly, with drinking and talking. I stood and talked with one of the two other people over 30. Elizabeth, ever organised, told me she had taken out liability insurance for the stripper pole.

The friends had arranged to begin the evening with an amateur burlesque show. We watched a slightly botched acrobatic routine to Rihanna’s song Jump. The next woman performed a pirate-themed striptease that concluded with her taping a pair of red cups to her breasts, filling them with Malibu, orange juice and coconut milk, and letting people drink from them with straws. Then, to Rihanna’s Birthday Cake, came a striptease that ended with the performer smearing herself all over with cake.

After the show, I walked into the massive slate-gray bathroom with its Jacuzzi and had a conversation with a couple about the dream of one day living in a backyard casita in Oakland with a composting toilet. I wandered back to the loft, where couples and threesomes had begun to pair off on couches. Nearby was a wheel of fortune that could be spun for instructions. After several conversations that felt like job interviews, I ended up taking turns spinning the wheel with a man. I did so with a slightly exhausted determination to get the show on the road. He was a bit younger. We spun the wheel, awkwardly obeying instructions to feed each other strawberries and kiss.

Then we went into the second room to do whip-its. I had never done a whip-it. My new friend explained how it worked: screw a small canister of nitrous oxide on to a stainless-steel whipped-cream maker. Exhale deeply, then inhale while depressing the handle of the machine, filling your lungs with nitrous oxide instead of oxygen. This produces a one- or two-minute high. Deprived of oxygen, the mind dissolves; physical sensation becomes acute, a goofy giddiness sets in. Whip-its are good for a sex party, because they do not impair sexual function and can heighten physical sensation, although I was advised not to do too many.

On my first whip-it, the man I had met lightly touched my arm, the feeling of his hands producing warmth and electricity while my vision broke into geometric patterns. During his turn, he asked that I kiss him. We made out for a while, doing the occasional whip-it. I felt airy and happy. We stood up with our hands against the wall and took turns smacking each other with a riding crop. Around us, groups of people lay together on beds and couches, or stood making out in corners. On a couch, a man lay across the laps of his friends, who formed a spanking train. I sat with Elizabeth and took a whip-it, after which she massaged my head while a man lightly shocked me with an electrified wand.

The after-party was at the apartment of one of Elizabeth’s partners, a man with whom she had exchanged I-love-yous. I had overheard a conversation between her and Wes before she left, where she had asked Wes if he would let her go on her own. It was a conversation that was difficult to listen to. I believed Wes when he cheerfully assented, but I also knew my own feelings would have been hurt. Chris was there, too, with his now steady girlfriend.

Elizabeth had slyly slipped me a condom, but I didn’t have sex. My then boyfriend in New York had not wanted me to attend the party at all. I was still thinking of myself as just a visitor, or rather neither here nor there, someone undertaking an abstract inquiry, but not yet with true intention. I regretted having been shy in my making out earlier at the sex party, that I had spent the night with one person instead of joining the cuddle puddle coalesced on the satin-sheeted bed opposite.

I wished I had other chances for this degree of experimentation, and wondered what it would feel like to be not a visitor to this scene, but a part of it. It had been easier for me to relax, because most of the people in the room had been strangers. Now I sat in a penthouse with a group of sleepy partygoers. We chatted and looked at the view. In the background was the sound of whip-its, of orgasms, of water falling from a shower into a porcelain tub.

• This is an edited extract from Future Sex, by Emily Witt, published next month by Faber & Faber at £16.99. To order a copy for £13.93, go to bookshop.theguardian.com, or call 0330 333 6846.