In a world where dating apps offer endless options and the labels for relationships keep evolving, the question of whether people are naturally inclined to have only one partner feels more relevant than ever.
Alina, a Romanian living in London, began pondering this after experiencing polyamory. Polyamory is the practice of having multiple partners at the same time, with the full knowledge and consent of all parties involved.
“I recently met someone who was very close to multiple partners from the start,” she explains. “It made me wonder: Why did we, as a society, end up in monogamous relationships?”
One way to explore our evolutionary path is to study our closest primate relatives and how they reproduced.
“Gorillas had multiple mates typically one male mating with several females,” says Dr. Kit Opie, an evolutionary biologist at the University of Bristol in the United Kingdom. “Each offspring in the group would have one father, but several females would serve as mothers.”
However, Dr. Opie explains that this isn’t an ideal reproductive strategy because it leads to high rates of infanticide.
“Predation is a dangerous part of gorilla life,” he says. “Male gorillas often kill babies that aren’t theirs to mate with the mothers sooner. That’s not exactly a strategy we’d want to replicate.”
Among other apes more closely related to humans like chimpanzees and bonobos females developed a different tactic. They mate with multiple males, creating confusion over paternity. This helps prevent infanticide, as no male is certain which infant is his.
Humans likely began with a similar system polygamy. But around two million years ago, things changed.
“That change was driven by climate,” says Dr. Opie.
“In sub-Saharan Africa, where our ancestors lived, the environment became drier, and much of the forest turned into open grasslands. To stay safe from predators, early humans had to form larger groups. With these complex group dynamics, their brains grew larger and lactation periods became longer.”
But large groups made paternity hard to trace.
“Females needed help from one male to raise their young. So they began to pair with a single partner,” Dr. Opie adds.
Is Monogamy the Best Way to Live?
According to Dr. Opie, monogamy didn’t arise because it was superior—it emerged because it was the most viable option for raising human children.
Large-brained, slow-developing human babies required more care than one parent could typically provide. Monogamy offered a practical solution to this challenge.
Still, while humans evolved toward monogamy, research shows that individuals often struggle to remain faithful to one partner.
“There are species that stay with one partner for life and don’t cheat. But they’re rare,” Dr. Opie says.
“Our closest monogamous relatives are gibbons. But gibbons live in isolated pairs, so both males and females can see when intruders approach.”
“In contrast, humans live in multi-male, multi-female groups, where detecting infidelity becomes much harder.”
In that sense, monogamy isn’t entirely natural, it’s a social adaptation. And like any adaptation, it comes with its own challenges.
The Science of Attachment
So what happens in our brains when we fall in love or struggle with commitment?
Sarah Blumenthal, a PhD candidate in neuroscience at Emory University in the U.S., studies prairie voles—a small, furry species known for forming lifelong pair bonds, much like humans.
Unlike their non-monogamous cousins, prairie voles have high concentrations of oxytocin receptors in the pleasure centers of their brains.
Often called the “cuddle hormone,” oxytocin is a neurochemical released during affectionate contact and physical closeness.
“If we experimentally block oxytocin signals in prairie voles, they struggle to form strong bonds and spend less time with their partners,” says Blumenthal.
Humans have a similar oxytocin system, which suggests that our brains are built to enjoy falling in love and forming close attachments.
But another chemical dopamine helps explain why we’re also drawn to novelty.
In the early stages of love, dopamine floods the brain, creating excitement and curiosity. As the relationship stabilizes, dopamine levels shift, which may explain why maintaining long-term romantic interest can be difficult.
Women with Multiple Husbands
Even though evolution may have favored monogamy, human cultures have always displayed a variety of relationship models.
Dr. Katie Starkweather, an anthropologist at the University of Illinois at Chicago, has documented more than 50 cases of polyandry—where a woman has multiple husbands from Nepal and Tibet to regions in Africa and the Americas.
Though polyandry is less common than polygyny (one man with multiple wives), Starkweather cautions against viewing it as abnormal.
“There are real economic advantages for women who have multiple partners. If the primary husband dies or is away for long periods as happened in some Indigenous North American groups it helps to have an alternative,” she explains.
In some cases, there are also genetic advantages to polyandrous relationships.
“In times when disease was common, having children with diverse genetic makeups increased the chances that at least some of them would survive,” she says.
However, polyamory is not without its difficulties. Maintaining multiple relationships requires emotional maturity, financial resources, and constant communication.
“It’s incredibly hard financially and emotionally for either a man or a woman to maintain multiple partnerships. That’s one major reason monogamy is still the dominant form of marriage,” Starkweather says.
Perspectives on Polyamory
Alina had one partner in her last relationship, but it didn’t work out. Now, in a polyamorous relationship, she faces a new set of emotional challenges.
“Jealousy can be really hard to deal with,” she admits. “But for me, it usually comes from a fear of dishonesty. If I know my partner’s being honest, the jealousy fades.”
Her partner agrees: “Jealousy isn’t the biggest issue. It’s the time and effort required to keep multiple relationships healthy.”
Still, both believe it’s worthwhile.
“There are no rules,” Alina says. “You’re forced to have conversations you’d never have in a traditional relationship—and that’s what makes our bond stronger.”
So, Are Humans Naturally Monogamous?
The answer seems to be both yes and no.
Throughout history, humans have adapted their relationship structures based on their environment, values, and needs. For some, monogamy provides emotional stability and clarity. For others, polyamory offers freedom, diversity, and support.
“Humans evolved to be flexible,” says Starkweather. “That flexibility—social, emotional, and behavioral—is exactly why we’ve thrived in every environment on Earth.”
So whether you choose one partner or many, it seems the real key lies in honesty, adaptability, and the capacity to love—and evolve.
