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Why Do Some People Date Multiple Partners at the Same Time?

A reader asked the following question: I'm interested in why some people like dating multiple people at a time and others only focus on one. Is it just for attention? Low self esteem? Or maybe it's survival of the fittest- don't stop on one until you're officially locked down?

 Dear Reader,

As you’ve probably noticed, the expectation in most cultures and societies is for individuals to be romantically involved with only one person at a time. This probably stems from the fact that marriage (which is almost universally defined as a union of two people) is frequently promoted as the “ideal” relationship state we should all be striving for. As a result, it tends to be the exception rather than the rule that people report engaging in non-monogamy.

For those who get involved with multiple partners simultaneously, why do they do it? There could be any number of reasons. Some might do it because they just aren’t ready to commit to one person, while some just aren’t sure what they’re looking for. Others might be driven by narcissism, sexual compulsion, or a need for validation. I should also note that some individuals simply feel like they can love multiple people at the same time, a practice known as polyamory.

In terms of what the scientific research has to say, you were on to something when you mentioned “survival of the fittest.” The field of evolutionary psychology thinks it is a natural human tendency to desire multiple partners, particularly if you are a man. In fact, research from around the world has shown that men have significantly greater desire for “sexual variety” (i.e., having a lot of different partners) over the course of their lives than women.1

Why do men want to be with so many people? From an evolutionary perspective, one of our major motivations or instincts is to produce as many of our own genetic offspring as possible in order to ensure that our genes are carried on to future generations. However, because the act of producing a child is, undisputedly, simpler for men than it is for women, the sexes tend to approach the mating game very differently.2 For men, the evolutionary strategy that makes the most sense is to sleep with as many women as possible because this maximizes their odds of having a lot of babies. For women, though, sleeping around indiscriminately makes far less sense. Yes, it might increase the chances of her becoming pregnant, but keep in mind that having a child requires a significant investment on the mother’s part, not only in terms of the 9 month pregnancy, but also in terms of the resources required to ensure that child’s health and survival after birth. Women who keep getting impregnated by guys who fail to stick around and help out with the kids may find themselves at an evolutionary disadvantage because they have to provide for themselves and their children entirely on their own (which probably proved exceptionally challenging in the days of hunter-gathers). As a result, the best evolutionary strategy for women is usually to be selective and hold out for a partner who will be reliable.

Thus, to answer your question, there are a lot of reasons why someone might choose to date several people at the same time, but at least for men, the desire for multiple partners might stem from an evolutionary drive.

Interested in learning more about relationships? Click here for other topics on Science of Relationships. Like us on Facebook to get our articles delivered directly to your NewsFeed.

For more on evolutionary psychology in particular, see here.

1Schmitt, D., et al. (2003). Universal sex differences in the desire for sexual variety: Tests from 52 nations, 6 continents, and 13 islands. Journal of Personality and Social Psychology, 85, 85-104.

2Buss, D. M., & Schmitt, D. P. (1993). Sexual strategies theory: An evolutionary perspective on human mating. Psychological Review, 100, 204–232.

Dr. Justin Lehmiller - Science of Relationships articles | Website/CV
Dr. Lehmiller's research program focuses on how secrecy and stigmatization impact relationship quality and physical and psychological health. He also conducts research on commitment, sexuality, and safer-sex practices.

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Reader Comments (8)

Evolutionary psychology needs to catch up with the modern world. In the article you say, "Research from around the world has shown that men have significantly greater desire for “sexual variety” (i.e., having a lot of different partners) over the course of their lives than women." First of all, this comment is way too general. As social scientists, it's dangerous to throw around broad statements like this. 'Around the world' is a big place. Second of all, could it be that men saying they want more sex and more partners has less to do with biology and more to do with the fact that due to societal constraints, women are not allowed to have/show these feelings, while men are encouraged to have them? Some research I have done into the flirting behaviour of various cultures shows that when women have economic freedom ( a situation so rare, that not much research has been done on this subject) like in Stockholm, the whole game changes. Sexually, women are more likely to 'act like men'. They want more partners for short term relationships and the same social stigma for women being sexual is not an issue.

You also back up the rusty stereotype that 'by nature' men want to spread their genes. But again, forgetting how modern conventions have impacted this, have you ever heard of something called birth control? It puts men and women on an equal playing field when it comes to the burden of raising non-existent children after a steamy night out. In fact, new research published in the Journal of Personality and Social Psychology, by Dr. Terri Conley at the University of Michigan, has shown that women are just as likely to say yes to a casual sexual encounter as men.

I find the field of evolutionary psychology frustrating and not helpful in our progression towards equality for men and women.

September 23, 2011 | Unregistered CommenterJean Smith

I can certainly appreciate your concerns about the limitations of evolutionary psychology, and I should point out that nowhere in this article do I say that it is THE explanation or the only explanation for why some people report greater desire for multiple partners. I mentioned several possibilities, but spent quite a bit of time discussing the evolutionary perspective because there has been a lot of research in this area and because it was an issue raised by the reader who submitted the question.

To address the specific points you made in your post, I should first say that my statement “research from around the world…” was not an exaggeration. The specific article I pointed to as support for this idea (Schmitt et al., 2003) included samples drawn from six different continents and 52 different nations. While that does not necessarily represent every single group of people in the entire world (which no scientific research ever does), it is about as close to a worldwide sample as I have seen in an academic paper. I take great care in the way I describe research so as not to overstep the bounds of the data, and in this case, I believe my characterization was fair given how diverse the samples were in the paper I cited.

Second, you point out the social structural critique of evolutionary psychology, which I feel is a perfectly valid criticism of the theory and something that should not be dismissed. In fact, when I teach about evolutionary psychology in college courses, I make sure to cover these alternative explanations and viewpoints (e.g., Alice Eagly’s Social Role Theory). I also spend time discussing what many see as shortcomings of the theory (e.g., How does it account for the phenomenon of homosexuality?). Like all theories, evolutionary psychology has its weaker points and, as I mentioned above, I do not believe it is the only way to explain gender differences in partner selection and I never meant to imply that by focusing on it in my article.

Lastly, I would like to point out that Terri Conley’s (2011) research does not categorically state that “women are just as likely to say yes to a casual sexual encounter as men.” To say that would not be scientifically prudent. In fact, Conley found that, in general, men were substantially more likely to say yes to a casual encounter than women (e.g., see Study 4 in that paper, where 73% of men said yes to such an encounter, compared to 40% of women). What Conley’s research suggested was that only when the conditions were right (specifically, when great pleasure was expected from a sexual encounter), the gender difference disappeared. However, the conditions are more likely to be “right” for men than women at any given time, due to a variety of reasons (e.g., the fact that men have an easier time achieving orgasm in a casual encounter). Thus, Conley’s findings should not be taken to mean that men and women are equally interested in casual sex all of the time, because that just wasn't the case. For additional information on this point, please consult the article “When are Women Into Casual Sex?” on this website.

September 23, 2011 | Unregistered CommenterJustin J. Lehmiller


Evolutionary psychology does not submit to the whims of gender equality nor adapt to the relatively rapid cultural shifts we undergo today. I support equal rights for women but that does not mean we should dismiss what the evidence supports. (Not proves, of course, there's a difference.)

This being said, to my great disappointment, the author has some faulty understandings of the most modern interpretations of social and evolutionary psychology from my brief perusal of his articles. (I've skimmed maybe 20) Specifically in this case, what has been fairly agreed upon as most advantageous for women evolutionarily speaking is having sex with "macho" men around ovulation and returning home to their "beta males" to help rear their child. This gives her the best chance to get the strongest genes while neatly replacing the relative unreliability of "playboys" for a more stable, dependable environment to raise a child.

February 23, 2012 | Unregistered CommenterJohn Doe

What has been fairly agreed upon as most advantageous for women evolutionarily speaking is having sex with "macho" men around ovulation and returning home to their "beta males" to help rear their child.

You're right that there is research showing that the type of men women find sexy varies across the menstrual cycle, and I've written about this in some of my past Science of Relationships articles (see here: Specifically, some studies suggest that women are more inclined to flirt with or fantasize about "macho" men when ovulating. However, among women in relationships, they only show these effects if they have a partner who is not particularly sexy or masculine to begin with. So, yes, for a woman who does not have a "macho" partner, evolutionary psychologists might argue that cheating during ovulation is an adaptive strategy--but for women who already have a masculine guy, it's important to note that this isn't necessarily the case.

February 25, 2012 | Unregistered CommenterJustin J. Lehmiller

Unfortunately, there are half-truths from all sources. Women were not biologically adapted to be monogamous, and there is much evidence in favor of this in both "The Myth or Monogamy" and "Sex At Dawn." Across species, the females have evolved to moan during sex as a mating call informing other male.members of the tribe that she is open for business. Feel free to research it. Humans are naturally polyamorous, and not deceptively so as some polygamists imply. The most primitive socities remain polyamorous to this day, and human women have concealed ovulation specifically to hide paternity. Children are meant to be raised communally. For yet more information on this, read "Sperm Wars." Men evolved to be sexually excited by the thought of his partner straying. Only did the expectations of agricultural societies change this.

August 14, 2012 | Unregistered CommenterAtheist

I would also add that women's propensity to have casual sex only when the sexual experience is guaranteed to be satisfying can be explained by the fact that women are less likely to orgasm during any sexual encounter than men are, rather than an overall tendency towards monogamy.

August 14, 2012 | Unregistered CommenterAtheist

Um, hi.

Woman here with two happy, open, simultaneous relationships here.

Just here to say we exist.

August 14, 2012 | Unregistered CommenterLily

I've been reading that this is true in many other species, not just humans, obviously this trait works for the purpose its intended for. I just got finished reading about a small marsupial species that creates healthier and stronger babies by "sleeping around".

July 25, 2013 | Unregistered CommenterElli Sanders

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