Australasian Science Magazine

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By Michael Kasumovic

Beauty is a subjective value, but studies are finding that mate choice is often affected by upbringing, self-esteem and previous experiences in courtship.

People are a complicated, and our understanding of what we find attractive in a partner is just as complex. Some prefer a perfectly coiffed hairstyle or a sly smile while others like bulging biceps or a smart sense of style.

In fact, the one thing we can be sure of is that there would be as many descriptions of what is attractive as there are people in a room! That’s because there is no simple definition of beauty: it is something personal to the individuals.

But if each of us has different perceptions of what we find beautiful, what is it that shapes these ideals? And more importantly, why do our preferences change as our situations do, especially as we age?

My research explores these questions in non-human animals because of the ease with which we can manipulate traits and subsequently observe which individuals mate. But how can understanding mate choice in crickets and spiders help us understand the complexity of mate choice in humans?

It turns out that decades of research on a wide variety of non-human animals can provide some interesting insight into understanding human mate choice. The one thing I’ve learned with my foray into human research is that despite the complexity that revolves around human behaviour and choice, we have more in common with other animals than we think.

Choice, Choosiness, and Success

Whether it is the brighter colouration in birds, more complex dances and songs in spiders, or the quality of the burrow created by fiddler crabs, females look for specific traits in partners. The critical thing to remember, however, is that it is not the traits themselves that are important, but what they indicate: that despite all the hardships in nature, the male suitor had survived and can express these outlandish traits so well.

Mate choice in males isn’t much different. Even though the females of most animal species are drab relative to their male counterparts, males prefer larger, healthier virgin females because they produce more offspring (and virgins will produce only their offspring).

Unfortunately, although both males and females know what they prefer, The Rolling Stones were right when they said that you can’t always get what you want. For every male and female that pair up, two individuals are removed from the mating population (at least for a while). If these are highly desirable individuals, the rest of the population will have to be happy with what is left. You can see why choices at a nightclub become grim as the evening comes to a close.

The interesting question in mate choice thus isn’t “what do individuals find beautiful?” or “who do they prefer?” but “with whom do they end up mating?” Understanding the factors that sway an individual’s actual choice from their preferred ideal can provide insight into how preferences change and how mate choice evolved, even in humans.

What Animals Can Tell Us About Mate Choice

Who an individual attempts to court generally revolves around how they perceive their own attractiveness relative to rivals. This perception is shaped by many different factors and even begins before an individual matures.

The nutritional environment begins to shape an individual’s later attractiveness as it provides the necessary fuel for development. But the importance of early life nutrition doesn’t end there as it also affects an individual’s choices.

A study by Marie-Jeanne Holveck and Katharina Riebel from the Centre of Evolutionary and Functional Ecology in France demonstrated that the nutritional environment affected the partners that zebra finches chose. There was a benefit to partnering with individuals from a similar nutritional history – nutritionally matched pairs laid eggs more quickly, which provides a better chance of successfully rearing offspring before the breeding season ends.

How the social environment affects development and maturation gets less attention. My research focuses on the importance of the social environment. Using male and female crickets I have shown that, just like athletes preparing themselves for the competition they will meet, immature crickets use the information they hear – the calls of adult males around them – to make developmental and behavioural decisions.

Males that hear more stiff competition develop larger to outcompete rivals in physical confrontations, and change how much they call as adults as they try to attract females. In the same environment, females mature faster, are pickier about what they look for in a mate, and make mating decisions more quickly. Even juvenile experience can shape what individuals find attractive.

Social encounters continue to affect mate choice after maturity. Females of many species demonstrate that interactions with males prior to mating alter their mate choice. Just like a visit to Ikea can alter your furniture preference (and your likelihood of remaining with your partner), females change what they consider a suitable mate depending on which males courted them previously.

And females aren’t only affected by who they encounter as mates, but also by the circumstances they encounter them in. Water strider males are voracious sexual predators – they attempt to mate with every female that comes along. The only way a female can exert choice is by fighting an unwanted male off – something females are quite good at.

Chang Seok Han and Piotr Jablonski from Seoul National University found that males evolved an interesting way to subvert females: slap the water as much as possible to attract predators while attempting to mate. Since females are closer to the water surface during the mating struggle, they are at a higher risk of being eaten if a predator arrives. As death is a worse result than mating with a sneaky male, females become less resistant, and therefore less choosy. In this way, males escalate environmental risks to induce a rapid change in female mating standards.

These animal examples demonstrate some of the many factors that can affect how individuals perceive themselves relative to rivals, and therefore who they choose to mate with. But surely these simple factors couldn’t affect the complexity involved in human mate choice?

What Does Love Have To Do With It?

We cannot ethically manipulate human traits and social interactions like we do with non-human animals. How, then, are we supposed to explore mate choice in humans? One way is to use the decades of research in non-human animals to carefully select human scenarios in which we can test specific questions in less intrusive ways.

For example, although we cannot split up siblings from a family and rear them in different familial environments, we can use adoption and foster cases, as well as naturally disrupted families, to examine the role of the social environment in development and choice. Interestingly, the parental environment has important effects on how young girls develop.

Age at menarche, is an important predictor of later life health in women. Young girls that experience menses earlier experience a host of negative effects, ranging from depression and substance abuse to breast cancer and obesity. It is thus a concern that young girls reared in the absence of their biological father attain menarche earlier. This effect is further amplified by the presence of step-fathers. Interestingly, Lynda Boothroyd and David Perret at St Andrews University demonstrated that teenage girls prompted to grow up quickly also prefer the faces of less masculine men.

Given that earlier menarche is associated with poorer health, the researchers argued that this preference for less masculine men was a result of females’ inability to compete for higher quality, more masculine men. It may also, however, be a change in preference for more feminine men that generally demonstrate higher paternal care and are less likely to emulate their dead-beat dad.

These studies demonstrate that, just like in zebra finches, the early juvenile environment can affect what humans choose. But can choice also be affected by our experience as adults?

Again, putting individuals in a room and cycling through potential partners at a university setting to see how social experience affects mate choice is neither ethical nor realistic. However, a quick internet search can provide access to a speed dating service where this kind of mate choice is the norm.

Nicole Beckage and colleagues from Indiana University did exactly that, and examined what factors affected whether individuals offered their contact details to potential partners. They found that individuals not only factor in their own attractiveness when making a decision, but that their previous experiences also moderated the decision to allow further contact. Interestingly, women tended to consider their own self-rated attractiveness more than men when making their decisions. In a way, this supports the idea that men, like water-striders, are profoundly opportunistic.

Finally, just like in water-striders, environmental risks can affect what females find attractive. A large cross-cultural study by Lisa DeBruine and colleagues from The University of Aberdeen found that women from developing countries preferred more masculine males. As developing countries are associated with greater health risks, they argued this was because women were searching for healthier males (as masculinity is associated with greater testosterone and potentially greater immunity).

My colleague Rob Brooks and I, along with several others, argued another possibility. In developing countries where there is a greater risk of health issues, there is also lower female empowerment and a greater risk of homicide. The preference for more masculinity in males may be a result of females searching for masculine males that can provide greater safety and care. More studies like this are necessary to more closely examine the role of health and risks to better understand how the environment truly moderates human preferences.

What about men? Given the limited evidence in non-human animals, do men moderate what they find attractive? Absolutely, and it seems that winning and losing in a competition affects more than just the male ego.

Although it would be difficult to gain volunteers for a study pitting men against one another in a modern day duel, almost every male has tasted victory and defeat – and continues to do so on an almost daily basis when playing video games. Brain imaging studies suggest that pathways that modulate self-esteem in response to feedback are similar to those that respond to winning and losing in video games. Video games thus offer a unique way to manipulate individual perceptions of ability by predetermining whether players win or lose.

Lisa Welling and colleagues from Oakland University have demonstrated that men who won contests in a first-person shooter video game were more likely to choose more feminine women than men who lost. These results suggest that winning in a contest, even a virtual one, affected a male’s perception of his own quality, and the mate he could attain. This may explain, at least in part, why men are drawn to playing violent video games on average more than women.

The Animals Within Us

Although it is satisfying to believe that the complexity that humans demonstrate is unique, the reality remains that we are still animals. Our biology was shaped in the same way as other animals so it should be no surprise that our choices are affected in very similar ways.

The most interesting aspect is that these studies highlight how seemingly inconsequential aspects of our everyday lives can change not only how we feel about particular traits in a partner but bias who we meet, and therefore who we date. I’m sure that clever new ways of examining mate choice in both human and non-human animals will continue to discover further subtleties involved in mate choice that will both enlighten and surprise us.