The thing that terrified me most when I was a grad student was the prospect of standing up in front of people and presenting my research. The first time I did this was in a group of fellow graduate students who were supposed to be friendly and supportive. After giving my talk, dry-mouthed and heart pounding, I croaked, “Has anybody got any questions?”

The first question was, “Doesn’t the existence of gay men like me show that Darwinian theory can’t really tell us anything about human behaviour?”

A reasonable question. Gay men don’t have the kind of sex that results in children being born so their genes are not passed on. So how come they didn’t “go extinct?” It’s a question which many evolutionary psychologists have puzzled over and written papers suggesting answers. Unfortunately, for me, this was not the topic of my research or my talk and I was completely unprepared for it. In my state of anxiety, I couldn’t remember any of the arguments well enough to say anything coherent.

So I just blathered out the first dumb thing that came into my head, which was, “I think that just about every gay man I know would make a terrific husband and father. Perhaps, in the past gay men just married women and had kids.”

My questioner, who I recall being very good looking, gave a smile which suddenly made me feel much calmer and said, “Yeah a lot of my female friends say that … that they think I would make a good husband.”

Several years later, at a talk given by Belgian philosopher Andreas De Block, I learned that my answer wasn’t as dumb as I’d thought. Doing sexual things with people of the same sex has a long history in humans and is common in some other animal species. As is always the case with humans, there was much cultural diversity. What the homosexual sex was like, who did it and whether or not it was approved of varied enormously from time to time and from population to population.

But it is a simple historical fact that, until recently, people who enjoyed same sex sexual relations also got married to people of the opposite sex and had children. The simplest explanation for why so many people enjoy homosexual sex today is that in the past it did not affect their reproduction.

The idea that some people can be categorized as “homosexuals” and that this type of person will not want to mate with members of the opposite sex seems to have been invented in Europe, probably in the last 200 years or so. It is highly unlikely that Oscar Wilde considered himself a homosexual even though he was sent to prison for committing the crime of sodomy in 1895.

I say this not because Oscar Wilde was married and had two sons, but because according to the Oxford English Dictionary, the word “homosexual” was first used as a noun in written English a mere 100 years ago, 12 years after Wilde died. If a word for something doesn’t exist, it is hard to imagine being one – even for Oscar Wilde. By contrast, the earliest writing that included the word “sodomy” dates back to 1297.

So when someone asks for a Darwinian explanation of why homosexuals exist they are really asking “Why did Europeans invent homosexuals in the 19th or early 20th Century?” I think I have the answer to this question and yes, it is inspired by Darwin’s theory.

It all has to do with economic development. After a population begins to industrialize, its members’ beliefs, values, and behaviours start to change in characteristic ways. They start to abandon their traditional attitudes and start to develop “modern” ones. Social scientists began to observe and write about these patterns of cultural change many decades ago and there is now quite a lot of evidence showing how patterns are similar and different in different populations. What social scientists can’t agree on is the reason for the change and why there is a pattern.

One reason that Darwinists should be interested in the modernization puzzle is that one of the patterns of change is particularly puzzling for us: People begin to behave less and less like Darwinian theory predicts. There is plenty of evidence (supplied by historians and anthropologists) that populations that aren’t economically developed do behave pretty much as if they are competing for fitness. For example, families tend to have as many children as they can afford and even quite young children are expected to work for their living and to look after their younger brothers and sisters. Women work hard too and their role as mothers and grandmothers is considered very important. Kinship is important. People expect to be able to rely on getting help from their family if they need it. If this is not available, friends and kind strangers may offer charity but no government organisations exist to provide help.

One of the first modern attitudes people adopt is that, even though they are getting richer, it is a good idea to have a small family so that they and the small number of children they do have can live more comfortable interesting lives. It’s easy to see when a population begins to adopt this new attitude; there is a drop in the number of children born per woman (what demographers call the “Total
Fertility Rate” or “TFR” of the population). The TFR of almost all human populations is now very low or falling rapidly.

It started first in populations of European descent (aka “The West”) where fertility began to decline in the 19th and early 20th centuries. Since then, Western culture has adopted many changes that seem to make people even less motivated or less able to compete for fitness. Parenting styles changed, children went to school, spending less time at home helping and learning from their elders. Motherhood ceased to be considered such an important job. Some women started to want to do work that was considered valuable and paid them money. Before long, women working outside the home became the norm. Marriages became less stable, making parental partnerships fragile. The invention of homosexuals was just one change in a complicated change process.

Another reason why Darwinists should be interested in modernization is that, like all cultural change, it is a Darwinian process. We inherit our culture from members of our population that lived before us, like we inherit our genes from our parents. And we pass cultural information on to others like we pass on our genetic information to our children. In the process of being passed down the generations, culture changes. In other words, culture evolves, just like the genes in a population. Cultural change is “descent with modification”, just like Darwin said. Culture changes a lot faster than genes change but if we want to understand why the change happens we can do similar sorts of analysis and testing we when we look at genetic change. We need to understand the forces that are pushing culture to change in certain ways.

It seems reasonable that economic development could be causing people to adopt modern ideas. But how and why is it happening? A view popular among social scientists who don’t take a Darwinian approach to understanding human behaviour (e.g. Ronald Inglehart) is that people’s beliefs and values change as a natural consequence of them getting richer and feeling more secure. They no longer need to worry about just surviving and so they start thinking about all the other things they can do with their lives. They do more different kinds of things and they become more tolerant of other people doing different kinds of things, including being a homosexual, if that’s what they want.

But this reason for the cultural change doesn’t make sense to Darwinists. Why would modern behaviour, small family size, and homosexuals be a natural consequence of wealth and comfort? We are descended from people who had MORE children when times were good, not fewer children.

An idea more compatible with Darwinian theory is that the process is triggered by the change in people’s social networks. The whole structure of human communities changes when a population undergoes economic development. People start to have jobs and schools to go to and they become connected with other communities by travel and communication technology. Before economic development people don’t just LIVE with their family, they WORK with them and LEARN from them. Being connected with a family, by birth, by marriage or both, is not just of great practical importance. It is socially important too.

In modern societies, people are aware of belonging to many groups. We’re employees in a business, students in a school, fans of a football team, and so on. But this is a completely new way of life for humans. For almost all of human evolutionary history, membership in a family was most people’s most important social identity. People were strongly influenced by other family members and they shared a common purpose – to keep the family going.

In this social environment, it is not surprising that communities maintained cultural norms that often demanded loyalty to family above one’s own interests and desires. A young adult was expected to marry the person the family chose for them. A woman was expected to get pregnant again even if she nearly died giving birth to her last child. In hard times, when the family can’t afford new mouths to feed, young adults are expected to help raise their relatives’ children. Getting pregnant by accident and creating a child sure to suffer poverty and malnutrition is a terrible sin. People may have loved and desired one another, but this needed to be controlled even in times of relative abundance. This is because the main purpose of life was not achieving personal fulfillment but turning resources into viable offspring – just like other animals and just as Darwinian theory predicts.

Economic development creates opportunities for new social groupings that compete with the family for people’s time and attention. As a result, family promoting norms begin to weaken. The change is not instantaneous, of course, because people still learn and to some extent hold on to the norms they picked up as a child. The first reaction to the increased wealth and security economic development brings is to have larger families and a population explosion ensues but that soon changes. Nowadays in only a few countries, mostly in Africa, are families large. Other changes follow in due course and the change is likely to continue. It is an evolutionary process and likely to take many generations to play out.

Even in the West, where industrialization began in the 18th century, culture is still changing rapidly and there is still much disagreement over “family values” issues, such as beliefs about homosexuality. The United States population seems to be particularly divided, perhaps because quite a large proportion of Americans are immigrants from countries like Mexico, where economic development occurred much more recently than in populations of European descent.

At the moment there is considerable concern in the West that the populations of many countries are slow to adopt what Westerners see as basic human rights. These people are beginning to enjoy the greater wealth and comfort that economic development brings so why aren’t they on board about things like “women’s rights” and “gay rights”? Some don’t even realize (or admit) that there are homosexuals in their countries! Some parents even think it’s OK to send their children out to work in factories!

This all makes sense if you realize that cultural change is evolutionary. It took Western culture quite a while to invent the homosexual and even longer before the homosexual marriage idea caught on. It is unreasonable to expect people of other cultures to adopt these ideas immediately just because Westerners tell them they’re right.

The cultural evolutionary process has obviously begun in most countries because the population has begun to adopt family limitation. Is there a way to know when they’re likely to pass through the subsequent stages of modernization? One way to get an idea is to plot the year fertility began to decline in a country against the proportion of people in the country that accept the Western idea of homosexuality. We can do this because a few years ago the Pew Foundation ran a global attitude survey when they asked a question about homosexuality.


In countries like the UK, where fertility began to decline over a hundred years ago, acceptance of the homosexual lifestyle is much higher than in countries like Iran which began the cultural change process much more recently. This may be why the president of Iran and many of the citizens do not believe there are homosexuals in Iran. People living in Victorian England wouldn’t believe they had homosexuals either.

Lesley Newson

Lesley Newson

Lesley Newson studies the cultural evolutionary process known as “modernization” which most human populations are now experiencing. She also works at being the mother of one child and the grandmother of two. Her first degree was in biology. After that she worked for over 20 years as a science writer and television producer before getting a PhD in psychology. She is now the honorary post-doc and wife of Peter Richerson at University of California, Davis


  • Nick Armenti says:

    What an informative piece!

    This may sound a bit wierd but –  most (not all) homosexuals, being predisposed to not pursue biological or genetic offspring, present an interesting notion, at least for me, that the concept of offspring might just be broader than what biological/ genetic offspring connotes. Perhaps reproduction via biological/genetic offspring is too restictive after all. You present the dynamics of cultural evoluton clearly above.
    I have been puzzled by the apparent evolutionary puzzle of homosexuality and have tried to understand it for some time. It seems that a partial explanation may lie in viewing homosexuals as people who contribute to the inclusive fitness of their own kin and that of others indirectly.
    When the idea of inclusive fitness is broadened to include one’s fellow humans, as within the family of man via a common human genome, then the gay community may be seen as contributing to the fitness of others through their cultural achievements that do in fact advance others fitness. Their reproduction through cultural “offspring” certainly are not genetic but may just be in the form of the memetic offspring they pass on into posterity as perhaps the metaphor of a “brain child” connotes. (For a listing of some homosexuals who have made important cultural contributions to their fellow humans Google “famous gay people”.)
    Hopefully, the demographic transition as it develops worldwide,with its associated increase in general intelligence (g) and enlightenment, will result in an increased appreciation of the evolutionary fitness-value of the homosexual population as deceptively indirect as thier cultural, memetic contributions to others may appear to be.

  • Pyers Symon says:

    Isn’t it also possible that another reason was that the punishments for homosexuality were so draconian? The Buggery Act of 1533 allowed for the death penalty and it remained law until 1861 with the last execution being carried out as late as 1836.  The pressure upon someone to “conform” and marry and raise children would be extremely high – given the potential consequences.

  • Nancy Blaker says:

    Nice piece.

    I am no geneticist or even biologist, so what I am going to say might be ridiculous. Anyway, reading this gave me a thought:

    As I understand it, homosexuality is partially genetic. Also, in societies where homosexuality is more accepted, I expect that homosexuals probably have fewer offspring (because they won’t marry someone from the opposite sex and have kids as easily. Of course I’m not saying that homosexual couples never have children). Is it then the case that in an environment where homosexuals can openly form same-sex couples instead of ignoring their orientation and forming an opposite sex couple, genes related to homosexuality are less likely to be passed on?

    That would be ironic.




  • Alan says:

    Consider this a test project for group-level selection. 
    At a larger scale, this will make for some interesting evolution going ahead – clearly a drop in fertility is good from a resource utilization aspect


    I made the same suggestion to explain the surprisingly high current level of homosexuality way back in 2003 in the letters section of ‘The Psychologist’ magazine. This is the house magazine of The British Psychological Society. I was very surprised at the reception it received from some members of that society. I was accused of homophobia and several subsequent letters expressed anger that the Editorial Board passed it for publication! There were also letters of support but I found the incident somewhat puzzling in a learned society and vaguely disconcerting.

    I continue to believe that the theory has merit. If this is indeed the case, and bearing in mind the much less homophobic zeitgeist in many countries, a corollary is that the incidence of homosexuality in those places may be expected to fall over time as the genetic component wains.

  • A homo says:

    Maybe i missed something here but…………one thing i can say as a gay man, STRAIGHT COUPLES PRODUCE GAY OFFSPRING! A suprising fact that no one mentioned. I am a product of heterosexuals, as i suppose 99.99% of lgbtqi people are! What a concept. While i do agree to a genetic predisposition to same-sex attraction, it is clearly mot a case of parental “gay genes” being passed to their offspring. Just from what i skimmed, it seems that the assumption you all seem to be making is that gayness can only come from gayness. The thought of which is utter silliness. As a matter of fact, at least in the data and personal experience, the offspring of gay/lesbian, gay/straight, etc seem to produce predominately heterosexual identified kids. You seem to be missing the point.

  • Ahmad says:

    Well, I was searching about sexual abuse issue of football players in UK which I came across this useful piece. As an Iranian who lived in England for a while I like to say it was sort of weird for me to see how eager are some young or even middle age British to homosexuality! After a while I found out that several politician, actors, singers…. are gay and some of them even talked about that in media. There were several movies and serials which barely showed homo and as an stranger all of them were weird and promote young people to do this without any shame. In Iran there may be few homosexual and there is a strong correlation between their believes and faiths as Muslim people and their homo affairs. I know some homosexuals have genetic problems especially transsexuals which some of them finally terminate in homosexuality but I am sure even in England most of people who are involved in homosexuality do not practically have strong believes in God, another world and religion. Try to find correlations between people believes and their tendency to homosexuality. If you find homosexuality a problem then try to make people more familiar with religion. Sorry for my low English influency

  • Denise Cummins says:

    Great article! I have a few comments:

    First, as noted by another commentator, straight people can and do produce gay children.

    Second, homosexuality can be congenital rather than genetic. Levels of sex and stress hormones impact brain wiring during gestation in the womb which impacts sexual orientation later on:

    Third, the author is certainly correct when she states that in social environments that forbid homosexuality, homosexuals enter into heterosexual marriages which yield children. Here are 14 famous gay men who were once married to women, some of whom had children:

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