A new cross-cultural study published in Scientific Reports, spanning 11 countries, looked at how much a partner’s sexual history actually matters in long-term relationship decisions. The findings confirm that people generally prefer partners with fewer past partners, and found that when those encounters took place and how sexual activity has changed over time made a significant difference. 

Importantly, the study found little evidence of a consistent sexual double standard, challenging one of the most entrenched assumptions in the discourse.

I recently spoke with Andrew G.Thomas, the study’s lead researcher, about the evolutionary roots of why humans care about sexual history, the surprising nuances revealed by the data and what the findings mean for daters trying to navigate conversations about intimacy today. Here’s a summary of our conversation.

From an evolutionary perspective, why do our brains care so much about someone’s “number” in the first place? What ancient risks was this psychological tendency trying to help our ancestors avoid?

From an evolutionary perspective, human psychology has evolved over long periods of time to help us cope with recurring adaptive problems in our environment. In other words, to mitigate recurring risks. In the case of this research, the risks we’re considering are essentially failures within romantic relationships. 

That might mean pairing off with and investing heavily in someone who isn’t truly invested in you and might cheat or look elsewhere. There are also important health risks, such as sexually transmitted diseases, which have been present throughout human history and can have major consequences for fertility.

Although in this paper we’re focusing on past partner numbers, humans are very good at recalibrating to modern cues. Take money, for instance. Our psychology didn’t evolve in a world with money, but we readily interpret it as a signal of status. So even though it’s a novel cue in evolutionary terms, we can still use it effectively in our judgments of others.

Previous studies have shown that people often prefer partners with fewer past sexual encounters. What was the key new dimension your research introduced to this conversation, and what was your central hypothesis about how it would change our perceptions?

You’re right that previous research shows “more is less” when it comes to sexual partners. People tend to be more skeptical of someone with a richer sexual history compared to someone with a more limited one. At the lower end, though, it’s not always so simple. 

Some studies have found that virgins were actually rated as slightly less desirable than those with one or two past partners. But overall, it tends to be a linear trend: the more sexual partners someone has, the less desirable they are perceived to be.

Back when I conducted my earlier research in 2016, two questions stuck with me. First, since we had only tested a British sample, was this a uniquely British effect or a more universal human one? Second, the partner number alone only tells part of the story. For example, six partners in the last six months is clearly a different scenario than six partners spread across 20 years. Everyone intuitively recognizes that distinction.

So our hypothesis in this new study was that risk fades with time. If someone had a rich, adventurous sexual past but it was long ago, and they now seem to have slowed down and are looking for a long-term relationship, they might be judged more favorably than someone who is currently in a very experimental phase. We predicted that the effect of past partner number would be moderated by changes in frequency of new sexual partners.

Your findings robustly confirmed that as a suitor’s number of past partners increased from 4 to 12 to 36, people’s willingness to enter a long-term relationship with them decreased. How consistent was this finding across the diverse cultures you studied, from China to Brazil to Norway?

The central “past partner number” effect turned out not to be unique to Britain. We replicated it across every culture we examined, including China, Brazil, Norway and others. The magnitude varied: in more socially and sexually conservative countries, the decline in interest was sharper, but the basic pattern was consistent everywhere. 

We didn’t find any culture where partner number didn’t matter, or where the association was reversed and higher numbers were judged more positively.

Perhaps your most interesting finding is about the pattern of a sexual history. Could you explain this? For instance, if two individuals both have 12 past partners, how does the timing of those encounters dramatically change how they are perceived as a long-term mate?

That’s right. The moderation effect with distribution was especially interesting. What we found was that people were more forgiving of higher partner numbers when much of that sexual history was in the past. So, someone with 12 past partners who slowed down and was now showing long gaps between relationships was viewed more positively than someone with the same number of partners but who had been very active recently.

By contrast, people were least forgiving of someone whose history showed the reverse pattern, perhaps long-term relationships with big gaps in between, followed by a recent burst of many partners. In other words, change in frequency matters: slowing down softens the negative impact of partner number, though it doesn’t erase it completely.

You mention patterns of “inertia” and “diminished returns” for those with multiple past partners. For a lay audience, what do these mean, and when do changes in sexual behavior start or stop mattering?

Some of the patterns we observed were curvilinear, not just straight lines. What I mean by “diminished returns” is that once the bulk of someone’s sexual history is in the past, pushing it further back doesn’t make much additional difference in how they’re judged. On the other hand, “inertia” captures the idea that if someone has had a lot of partners very recently, it takes a while for perceptions to shift.

So, if someone had 36 partners in the past six months, they’d be judged about the same as someone with 36 partners in the past seven or eight months. But once you get out to a year, two years, or three years, then enough time has passed that people start to view them more favorably.

The idea of “body count” is often tied to a sexual double standard, where women with an extensive sexual history are judged more harshly than men. Did your data show consistent evidence of this in how people evaluate long-term partners?

This is an important question. Online discourse often emphasizes a sexual double standard. Namely, that men are lionized for having many partners while women are demonized. We actually found very little evidence of that in our data.

The distinction I draw is between societal judgments and individual judgments. When you ask people what society thinks, they readily describe a sexual double standard. But when you ask individuals what they think and how they would act, those differences largely disappear. In our samples, there was little evidence of consistent sex differences in personal evaluations.

How does a person’s openness to casual sex, what you call “sociosexuality,” influence their judgment of a partner’s sexual history? Why does this trait not completely override concerns about past sexual behavior?

Sociosexuality, someone’s desire for uncommitted casual sex, was a great dimension to test. We suspected that people high in sociosexuality might actually prefer partners with more recent sexual activity, since that could signal greater availability. But that wasn’t what we found.

Instead, people high in sociosexuality showed the same overall pattern as the sample at large, just in a muted form. They were less judgmental about partner number, but still distinguished between, say, 4 and 36 partners. So sociosexuality softened the effect but didn’t eliminate it.

What advice would you give to individuals navigating dating and long-term relationships in today’s world, especially when it comes to interpreting a partner’s past without jumping to conclusions or judgment?

My advice would be: don’t take some of the online rhetoric you see about “body count” too seriously. The videos and posts that go viral tend to be the most shocking or extreme, and they don’t reflect how most people actually think.

In real relationships, conversations about sexual history usually happen later on and in more nuanced ways. Our study shows that people are receptive to qualifiers beyond just the raw number. If someone’s priorities have shifted over time, or if their behavior has changed, that context matters. So if you ever do find yourself talking about body count with a partner, it may be worth highlighting how your approach to relationships has changed or evolved. 

Fundamentally, the message is that people are more open and forgiving than the online discourse would suggest.

Given that sexual history discussions are often framed negatively in online discourse, how can your findings help promote more empathetic and informed conversations about intimacy and relationships?

I think this paper can be a useful counterpoint to some of the harsher online conversations, especially those in the manosphere. A lot of that discourse leans heavily on the idea of a sexual double standard. Our findings challenge that. Yes, partner number matters, but context matters too, and the double standard is nowhere near as prominent as it’s often portrayed.

So I hope people use this research as an open-access resource to push back against some of that rhetoric. If someone is confidently promoting the sexual double standard narrative, it might be a sign they haven’t really looked at the data.

Much of the most recent work looks at how people integrate across different dimensions. Do they prioritize some traits, or do they average across all of them?

Sexual compatibility sometimes enters into that discussion, but sexual history, despite its obvious importance, has been largely excluded. So I hope this research sparks more attention to sexual history as part of that bigger puzzle. Integrating it with the wider mate preference literature could give us a fuller picture of how people make choices, and that in turn could support healthier, more realistic conversations about relationships.

Are ideas like “body counts” hindering your love life? Take this science-backed test to learn more: Brief Sexual Attitudes Scale