How to Understand Girls (Scientists Explain)

Girls are complicated. 

After spending our teens obsessing over the opposite sex, we can confess that we still don’t understand women. (To be fair, girls probably find guys to be just as confusing.)

Why are girls crazy about commitment? And why are they attracted to the bad boys—who offer zero commitment? Why do some girls cheat on their boyfriends? What do women really want?

We do love our girlfriends, but unless we try to understand the similarities and differences between girls and guys, we will repeatedly suffer from loneliness, disappointments, and heartbreak. 

Sadly, there are no easy answers. To understand girls, we need to dig a little deeper and understand how humans evolved.

Long Long Ago . . .

In The Evolution of Desire, the evolutionary psychologist David Buss observes that evolution is difficult for us to understand because of how we experience time. (Heads up! I will be referring to Buss’s spectacular book a lot). In his words:

Our cognitive and perceptual mechanisms have been designed by natural selection to perceive and think about events that occur in a relatively limited time span—over seconds, minutes, hours, days, sometimes months, and occasionally years. . . . Evolution, in contrast, occurs gradually over thousands of generations in tiny increments that we cannot observe directly. To understand events that occur on time scales this large requires a leap of the imagination . . . 

And that’s precisely what we will do—imagine the lives of our ancestors with their struggles and opportunities. 

In our fast-changing world, however, it might seem a waste of time to think about the ancient past. Here are two facts to change your mind.

We Are Not Adapted To Modern Society

In The Red Queen, the science journalist Matt Ridley explains that we are stuck with brains that were ‘designed to exploit the conditions of an African savannah between three million and 100,000 years ago’.

For 90% of the 300,000 years of our existence, we—homo sapiens—have lived as hunter-gatherers. Ancestors of our species started hunting and gathering even earlier, two million years ago. During this time, our minds and bodies evolved slowly through the process of evolution.

As evolution is a very slow process, it can’t keep up with the recent changes in our environment. Modern society is just such a change. Consider, we have lived in cities for less than 1,000 years and agriculture was invented 11,500 years ago. These changes account for a ‘mere eyeblink in evolution’, emphasises Ridley.

In short, we are not adapted to modern society.

Our Psychology Is Designed for Reproductive Success

We are all descendants of humans who were interested and successful in having children. It can’t be any other way since early humans who were uninterested or unsuccessful in having children didn’t leave any descendants.

Hence, our psychology has been shaped by millions of years of evolution to be successful at having children. Even if we don’t consciously want to have children, we have tastes and preferences that maximise reproductive success.

Now that we have the intellectual tools to understand our love lives, let’s go over the confusing questions about female psychology.

  1. Why Do Guys Charm and Girls Choose?
  2. What Do Girls Want? 
  3. What Do Guys Want? 
  4. Why Do Girls and Guys (Sometimes) Cheat?  
  5. Why Are Girls Jealous? 
  6. Why Are Guys Jealous? 
  7. How to Get Your Happily-Ever-After

1. Why Do Guys Charm and Girls Choose? 

Let’s start with the obvious: girls are super picky when it comes to whom they are attracted to. Guys are much less choosy about whom we find desirable. ‘For example, men often express the desire and willingness to have sex with an attractive stranger’, writes Buss, ‘whereas most women refuse anonymous encounters . . .’ 

Put another way, guys charm and girls choose. In the paper Parental Investment and Sexual Selection, the evolutionary biologist Robert Trivers explains the reason for this. It is because of how reproduction happens: biologically, reproduction is expensive for women and cheap for men. 

When a woman has sex with a man, she risks getting pregnant. She would carry the foetus inside herself for nine months, breastfeed the baby for years, and take care of the child for more than a decade until it reaches maturity. Conversely, a man loses only a couple of minutes of his time by having sex.

In our evolutionary past, women who were highly selective about whom they had sex with, ensured they had children with the right partner. In other words, choosy women were reproductively more successful than women who weren’t. As a result, girls today have inherited choosiness from our ancestors. Girls are interested in finding a quality partner, not in increasing their quantity of partners.

The opposite story holds true for us, guys. In our evolutionary past, men who were able to have children with multiple women had more reproductive success than men who had only one partner. As a result, guys today have inherited a desire for variety from our ancestors. Guys are interested in increasing their quantity of partners. 

Today, casual sex is less risky due to contraceptives and the costs of reproduction can be more evenly spread between the sexes with the help of paternity tests and child support laws. But our evolved psychology has yet to adapt to such recent developments.

2. What Do Girls Want?

We know girls are picky, but what criteria do they use to pick their partners?

Girls choose their partners based on two sets of qualities: good genes and parental ability. Buss has written about the indicators of each.

Indicators of good genes in a man (from the perspective of mating) include height, strength, broad shoulders, V-shaped torso, broad lower jaw, strong brow ridge, facial and body hair, deep voice, symmetrical features, high energy level, athleticism, health, oral fluency, social skills, and intelligence. On the other hand, being a close relative is a turn-off, as inbreeding leads to genetic abnormalities in children.

Women seek men with good genes so that they can pass these genes on to their children.

Indicators of parental ability include a willingness to commit, emotional stability, kindness, compatibility, generosity, mature age, ambition, wealth, and social status. On the other hand, indicators of a lack of parental ability include having a pre-existing relationship, children from a previous relationship, a reputation for promiscuousness, and a bad temper.

Women seek men with good parental ability so that their children can get a good start in life and, ultimately, reach their full genetic potential. 

Research conducted by Buss and his colleague has led to intuitive results. When seeking casual sex, girls prioritise indicators of good genes, but when seeking a long-term relationship, they prioritise indicators of parental ability.

The Response of Guys 

Throughout history, women have preferred men with indicators of good genes and parental ability, and this has put evolutionary pressure on men to respond to what women want.

Buss has identified the the ways of highlighting the indicators of good genes.

Men advertise their physical strength and athletic prowess. Examples include ‘flexing muscles, playing sports, mentioning feats of athletic prowess, and lifting weights’.

They advertise their intelligence too—through their humour, large vocabulary, artistic ability, and creativity.

Buss has identified the ways of highlighting the indicators of parental ability as well.

Men demonstrate their commitment. Examples include ‘spending a lot of time with a woman, seeing her often, dating her for an extended period of time, calling her frequently on the phone, and texting or emailing her frequently’.

They compete with one another for social status and ‘are particularly concerned about status, reputation, and hierarchies’.

Men also acquire and display wealth. Examples include ‘showing a high earning potential, flashing a lot of money, driving an expensive car, telling women how important they are at work, and subtly revealing their accomplishments’.

Finally, not all men respond to women’s preferences in the same way. The strategy of a man blessed with ‘sexy’ genes might be the polar opposite of one blessed with parental ability. ‘Some men are cads, preferring to mate with many women while investing little in each’, writes Buss. ‘Other men are dads who prefer to channel all of their resources to one woman and her children.’

3. What Do Guys Want?

Guys are not as picky as girls, and they care more about the quantity of their partners. But that doesn’t mean they don’t have any preferences.

Men choose women based on their reproductive capacity, i.e., their ability to have children. A woman’s ability to have children, in turn, depends on two things: youth and health. 

For ancestral men, the easiest way to judge the youth and health of a woman would have been through visual signs—’full lips, clear skin, smooth skin, clear eyes, lustrous hair, and good muscle tone’, writes Buss. Facial symmetry is another important sign.

Men’s preference for body shape varies across cultures. In cultures where food is scarce, Buss notes, men prefer plump women, while in those where food is abundant, men prefer slim women.

In all cultures, however, men prefer women with large breasts and wide hips. ‘Death during infancy due to a mother’s milk shortage would have been common before modern affluence—and still is in some parts of the world’, explains Ridley. ‘Death of the mother and infant from a birth canal that was too narrow must also have been common.’

Men also prefer women whose waists are narrower than their hips. ‘Irrespective of whether a woman is thin or fat, men prefer someone whose waist measurement is about 70 per cent of her hip measurement’, writes the evolutionary biologist Robin Baker in Sperm Wars.

Whether it’s for casual sex or a long-term relationship, men use the same criteria for evaluating mates. For casual sex, however, men lower their standards—a strategy to gain more partners.

The Response of Girls

Throughout our evolutionary history, men have had to adapt to women’s preferences and women, in turn, have had to adapt to men’s. 

Women have responded to men’s preferences by highlighting their youth and health. They have done so through an interest in fashion, makeup, dieting, fitness classes, anti-ageing products and, even, cosmetic surgeries. 

Buss gives us examples of how women enhance their appearance in response to specific preferences of men:

Because flushed cheeks and high colour are cues that men use to gauge a woman’s health, women rouge their cheeks artificially  . . . Because smooth, clear skin is one of men’s evolved desires, women cover up blemishes . . . Because lustrous hair is one of men’s evolved desires, women highlight, bleach, tint, or dye their hair . . . Because full red lips trigger men’s evolved desires, women apply lipstick skillfully . . . And because firm, youthful breasts stimulate men’s desires, women obtain breast implants . . .

4. Why Do Girls and Guys (Sometimes) Cheat?

Some things about relationships are not nice. Being cheated on by the person you loved is painful, to say the least. It’s also something that is difficult to talk about.

Nonetheless, the harsh truth is that it does happen in some relationships, and we need to understand why.

Why Do Girls (Sometimes) Cheat?

First, let’s go over two of Baker’s observations.

A woman doesn’t always get her first preference. ‘[M]ate selection is complex, particularly for a woman.’ The partner she wants may not be interested in her or may already be committed to someone else. She would then employ an old and effective strategy called compromise and choose the best partner available to her. 

People change. A lot can happen in a lifetime. The partner to whom a woman was once so attracted could lose value in her eyes. He may fail ‘to live up to the potential he had shown when she committed’ to him.

With these observations in mind, let’s look into our evolutionary past, once more.

Suppose there lived a woman whose partner had all the indicators of parental ability. He showed every sign that he would be a doting father to her children and would shower them with his undivided resources and attention. In a cruel twist of fate, however, the same man completely lacked indicators of good genes. 

Our imaginary woman could increase her reproductive success by having an affair with another man, chosen specifically for his good genes. If she could keep her affair a secret, she would get the best of both worlds—her children would benefit from the best genes and the best parenting available

In scientific terms, cheating was possibly an adaptation that helped ancestral women to solve the reproductive problem of securing, both, good genes and parental investment, for their children. And if this strategy had indeed led to greater reproductive success in the past, then modern women would have inherited this sexual strategy—one of many—as a part of their evolved psychology.

The intimate lives of couples were studied by Baker and his colleague. They made three startling observations that support this hypothesis (that women have affairs to access better genes). First, they found that cheating women were more likely to have encounters with their secret lovers during the fertile phase of their menstrual cycles. Second, they found that if a woman has an orgasm during sex, it increases the chance of conception and, finally, they found that cheating women have more orgasms with their secret lovers than with their long-term partners.

What Buss describes as the ‘economics of the mating marketplace’ also support this hypothesis. Since way more guys than girls are interested in casual sex, a woman in search of such an encounter can afford to be extra choosy. In other words, a woman can obtain a more desirable mate by offering casual sex than by demanding a long-term commitment.

Why Do Guys (Sometimes) Cheat?

Ancestral men sometimes cheated on their partners simply to increase the number of their children. Remember, a man can increase his reproductive success by having children with multiple women

Whereas women cheated to have better children, men cheated to have more children. An ancestral man, however, would have been able to cheat only if there was at least one woman around who was willing to engage in a casual affair with him.

As in the case with women, if opportunistic cheating had increased the reproductive success of ancestral men, then modern men would have inherited this strategy as a part of their evolved psychology.

5. Why Are Girls Jealous? 

As humans have always lived in groups, the risk of a partner cheating was always present. Buss believes that one of the reasons the emotion of jealousy evolved was to protect us from the consequences of having an unfaithful partner.

Any ancestral woman who had an unfaithful partner faced major risks. The cheating partner may ‘redirect his resources and commitment away from her and her children and toward another woman and her children’, writes Buss. 

Therefore, women who got furious at signs of unfaithfulness and acted strongly to prevent it had greater reproductive success than non-jealous women. 

In short, ancestral women were jealous to ensure the commitment of their partners’ support. And modern women have inherited this jealousy from their ancestors. 

6. Why Are Guys Jealous? 

Men are jealous because of the problem of uncertain paternity—a woman is 100% sure that her children are hers, but a man is not. 

An ancestral man who had an unfaithful partner faced the ultimate reproductive risk. He may devote a lifetime of parental investment into raising another man’s child! 

Hence, jealous and possessive men had greater reproductive success by avoiding the consequences of a cheating partner. Modern men have inherited this jealousy from our ancestors.

There is one last difference in jealousy between girls and guys. Girls get jealous over emotional cheating (‘Do you love her?’), and guys get jealous over sexual cheating (‘Did you have sex with him?’), writes Buss.  

7. How to Get Your Happily-Ever-After

Happy Couple

Now you know our evolutionary story and it is, disappointingly, unromantic. Biologically, we all seem to be calculating, manipulative, and hell-bent on maximising our own reproductive success. Nevertheless, all hope is not lost.

Here are some optimistic implications of human nature.

Ignorance is not bliss. ‘[A] realism about the imperfect emotions we actually have may bring more happiness than an illusion about the ideal emotions we wish we had’, suggests the cognitive psychologist Steven Pinker on human nature, in The Blank Slate.

Biology is not morality, points out Pinker, again. Just because there are biological explanations for infidelity and jealousy doesn’t mean that they are virtues which should be encouraged.

We are not slaves to sex roles dictated by evolution‘, writes Buss. Just because we have inherited tendencies to be unfaithful in certain situations and jealous doesn’t mean that we have to be that way. On the contrary, we can use what we have learnt to create better relationships. For example, knowing what causes jealousy can be the first step towards creating trustful relationships, Buss observes.

Men and women are similar in many ways. We do belong to the same species, after all. We are similar but not the same, and understanding our differences is a positive step.

Evolutionary biology even has some suggestions for securing a happily-ever-after. For these guidelines, we turn to Buss, one last time.

  • Have children, since they ‘align the interests of a man and a woman’. 
  • Remain faithful, since cheating will open up a ‘chasm of conflicting interests’. 
  • Be kind, since ‘people worldwide depend on kindness not from strangers, but rather from their mates.’
  • Understand and fulfil each other’s desires, since those who do have happier relationships. 

Wrapping Up

When I first read evolutionary psychology, it blew my mind. So many confusing things about love finally made sense.

Brilliant and hardworking scientists have discovered the story of our past through decades of research. Without knowing this story, girls will always be a confusing mystery. 

And, of course, evolutionary psychology does make generalisations about the sexes. All women aren’t clones of each other, neither are all men. We find many individual variations in the behaviour of people, but evolution still explains a lot of what we see in our love lives. 

The process by which the love lives of our ancestors have shaped our minds and bodies is called sexual selection (with evolutionary psychology being the study of how the twin processes of sexual selection and natural selection have shaped our minds).

Everything that I know about how sexual selection has designed our evolved psychology I’ve learnt from three books: Buss’s The Evolution of Desire, Ridley’s The Red Queen, and Baker’s Sperm Wars.

These books have many ideas that I haven’t discussed here, so I recommend that you read them as well.