Unlocking the Secrets of Mating Using an Evolutionary Lens

Evolutionary theory has a lot to say about sex and relationships and can often explain mating phenomena in a way that no other theories can. Here are five key evolutionary theories that are the central pillars of my undergraduate course on romantic and sexual relationships. These are some of the most well-researched and validated theories; understanding them will fundamentally change how you view relationships.

1. Evolutionary Mismatch

Despite thousands of years of cultural development, modern-day humans remain anatomically similar to archaic ones, and that includes the inside of our skull. For the most part, our stone-aged brain is well adapted to modern problems—navigating complex social situations and avoiding disease and death. But the modern world also contains problems and situations so far removed from those experienced by our ancestors that our ancient psychology struggles to cope with them, leading us to act in ways detrimental to our health and well-being.

We call this concept “evolutionary mismatch.” My go-to example of mismatch involves food—our taste preferences were designed to draw us toward calorie-rich foods such as honey and fat, which were relatively rare for our hunter–gatherer ancestors to come by. In the modern environment, where doughnuts and hotdogs are both cheap and plentiful, our preferences don’t consider themselves redundant and switch off. Instead, they remain active, leading us down a pathway to obesity if we're not careful.

Within the mating domain, mismatch occurs around things like mate choice. We now have access to thousands of potential partners through dating websites and are expected to make these choices alone, very different circumstances from how our ancestors chose their mates. You can read more about that in my piece Why Modern Life Makes Finding Love Feel Like Swimming Upstream.

2. Error Management

You’re sitting at your desk and see something small and black out of the corner of your eye. Without time to consider whether it’s a spider or lint, you react and jump to the side. It turns out it was lint and you made an error, but not a very costly one.

When it comes to threat detection, errors come in two types—either you react to a nonexistent threat or fail to react to a real one. Because one type of error is more consequential than the other, humans have evolved to err on the side of caution.

In the mating world, this can help explain why we often suspect infidelity when it isn’t there and, in the case of men, perceive sexual interest in others when they are trying to just be friendly (something we call the sexual over-perception bias).

3. Parental Investment

Parental investment theory explains sex differences in behavior across the animal kingdom, and humans are no exception. At its core, it’s the idea that the sex that invests the most in offspring will be more “sought after” than the sex that invests less. A consequence of this is that when there are large gaps in investment between males and females, then they will evolve to be quite different—males might become larger and act more aggressively to compete for access to females, for example.

Parental investment theory is often used to explain sex differences in humans because women have to invest more resources (time, energy) into their offspring by default (due to pregnancy and nursing) while men's minimum investment is courtship, effort, and semen. However, it’s important to know that the parental investment of both sexes tends to go well beyond the minimum. Men tend to stay in their children’s lives and invest heavily in them through protection and resources, for example. Thus, human sex differences in body and psychology, while real, tend to be modest compared to other mammals.

4. Sexual Strategies

According to this theory, humans have two mating strategies or “styles”—long-term and short-term. Most have some level of interest in both types of mating, but their mating psychology will change depending on which strategy they are using. For example, when men and women are looking for a long-term partner, they will prioritise someone who is kind, good with money, and likely to be a faithful partner. In contrast, those seeking short-term relationships care less about these things, largely because they are irrelevant for a brief relationship. Instead, they prioritize people who might give them quick sexual access, are generous with their gifts, and are physically attractive.

The sexual strategies lens is an important one because people often try to appeal to the desires of someone with a short-term mating style when actually wanting a long-term partner. For example, they may offer sexual access and lavish gifts early on in the relationship only to be surprised when it turns into nothing more than a one-night stand. Similarly, people might focus too much on physical attractiveness and “sexiness” in a partner only to be surprised when the people they date leave or cheat.

5. Strategic Pluralism

Related to sexual strategies theory, this theory helps us understand a bit more about when people might choose short-term mating over long-term mating. There are some life and personal circumstances in which one type of mating is a better fit for someone than another. For example, young people tend to engage in a lot of short-term mating early on as it gives them an opportunity to understand what their mate value is before they choose a long-term partner.

Similarly, in environments where parental care from both parents provides a big boost to the development of a child, people tend to focus on long-term relationships. In contrast, when the benefits are relatively low—such as in very safe environments or extremely dangerous ones—people tend to focus more on short-term relationships.

Evolutionary theory offers a unique perspective on relationships and can explain many of the behaviours and choices we make in our romantic and sexual lives. The five key evolutionary theories discussed above provide insight into how our ancient past continues to influence our behaviour and decision-making in the modern world, from mate choice to the detection of threats. Understanding these theories can fundamentally change how we view relationships and provide a deeper understanding of our own behaviours and those of others.