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LGBT Evolution
by Harry Earle

Charles Darwin has gone down in history as the ‘father of evolution’. Ideas about evolution had been around since the time of the ancient Greeks, but by the mid 19th century, no-one had come up with a convincing explanation of how the process of evolution actually worked or the huge implications behind it.

Darwin and Alfred Wallace came up with the process of natural selection completely independently, at the same time. Darwin is the one to go down in history because he published On the Origin of Species, a book which explained the mechanism of natural selection and provided examples of evolution throughout the natural world. One of these examples was the fact that modern humans share a common ancestor with apes, something that many people of the time and some unfortunate people of today found hard to accept.

In the 1940s, the theory of evolution was updated to include genetic explanations, so a current definition of evolution is: a change in the frequency of alleles in a population from one generation to the next. Evolution occurs at every instance of sexual reproduction – the baby has different genes from those of its parents.

There are two main components to the theory of natural selection: survival and reproduction. These are united in the concept of Darwinian fitness: The probability of surviving to breed times the number of offspring produced. Darwinian titness can therefore be raised by increasing the likelihood that your children will breed, or increasing the number of children you have. So now we know what ‘fit’ individuals are, let’s look at how natural selection works.

We start off with a trait appearing through a mutation or favourable combination of genes that increases Darwinian fitness:

1. Trait appears in an individual (opposable thumbs)
2. Trait increases Darwinian fitness (useful opposable thumbs)

This means the trait does one of two things. It increases the chance of breeding, or it increases the number of babies one has. In this example, the opposable thumbs increase the chance of surviving to breed as they better equip the individual to deal with the environment, through the use of tools etc.

3. Increased reproductive success
4. Opposable thumbs spread through the species
5. All of the species has opposable thumbs

Importantly, this is not just how traits appear but also how they disappear. Any deleterious or harmful trait will become rarer and rarer through natural selection.

That’s how beneficial traits evolve, but where do LGBT people fit in there? Well yes, sex serves an important purpose other than reproduction. Sex builds and maintains relationships through the giving and receiving of pleasure, in fact if you look at the human race, the vast proportion of all sexual encounters are not efforts to reproduce!

This is also true with same-sex relations. So the question is, how did homosexuality spread throughout the human race by way of natural selection if LGBT people aren’t motivated by their sex drives to breed?

It’s clear that homosexuality is useful or beneficial in some way because it has evolved in a large number of social, relatively intelligent species. So far, around 1500 species have been cursorily observed displaying homosexual behaviour, but its only been studied in about 500 species. A few of the species that do engage in same sex behaviour are sheep, deer, reindeer, moose, giraffes, pronghorns, kobs, waterbucks, gazelles, oxen, goats, bison, zebras, warthogs, peccaries, elephants, lions, cheetahs, foxes, wolves, beers, hyenas, kangaroos, wallabies, koalas, dunnarts, squirrels, chipmunks, marmots, cavies, hedgehogs, bats, dolphins, seals, sea lions, walrus, manatee, and of course in primates.

In some of these, same-sex matings are relatively uncommon, in others, very common, sometimes accounting for 50% of all matings. In one species, bonobos, intelligent and highly social primates, everyone engages in homosexual activity.

So far, very little work has been done on the subject, but a number of suggestions have been made as to the reasons for the evolution of homosexuality and bisexuality:

• Homosexuals are ‘helpers at the nest’ - i.e. we stay within our family and help raise our siblings, who then go on to reproduce. This is implausible since we don’t lack a sex drive, it is simply directed elsewhere. Helping at the nest also does not explain why helpers would be specifically gay or lesbian either.
• Homosexuality in males results from a recessive ‘gay gene', i.e. there is a gay male gene that offers some unknown beneficial adaptation in women. So women carry the gene which results in which causes homosexuality when they go on to have sons.
• Homosexuality is a bacterial infection – while being completely preposterous, this has been suggested by a molecular biologist that went on to say that we may eventually be able to eradicate the infection with an antibiotic.
• Homosexuality is a genetic defect –

This has been the main scientific argument against homosexuality and as such I’ll review it in more depth.

There are two criteria that a trait such as homosexuality must fulfil in order to be a genetic defect – it must be rare, and it must always be deleterious or harmful. In fact, if a trait is harmful, then it is going to be rare – the two go hand in hand. This is because any harmful trait will constantly be selected against by natural selection. Once it is completely removed by natural selection, the only way it can reappear is by a mutation. The rarity of a genetic defect is set by two factors – the rate of formation by mutation and the rate of elimination by natural selection.

The harmfulness of a trait is measured by the reduction in Darwinian fitness, remember – the probability of surviving to breed, times the number of offspring produced. If a trait causes a 100% reduction in Darwinian fitness, it is lethal. If a trait is lethal then it only occurs as often as the mutation rate which is one in a million.

If the trait causes a 10% loss in fitness then its frequency rises to one in one hundred thousand people.

Even a trait that only causes a 5% loss in fitness will eventually become as rare as one in 50,000 people. This is taken as the conventional threshold at which a trait can be considered a genetic defect. If a trait causes a 1% loss in Darwinian fitness, it would be very difficult to detect in someone because they would not be noticeably different from anyone else. Even a 5% loss would be quite hard to detect.

Now, homosexuals are a lot more common than 1/50,000. The newest estimates are about 1/20. Homosexuality has also been shown to be adaptive in other cultures, in ancient Greece for example. And also homosexuality hasn’t been proven to be a solely genetic trait at all! So we can definitely discount this explanation for homosexuality.

But what about transexuality? So far very little scientific research has been done on transexuality and as a result we have hugely varied estimates of rarity for transgendered people, ranging from as rare as 1/30,000 to as common as 1/500. At the highest estimates, transgendered people are far too common for transexuality to be considered a genetic defect. At the lower estimates though, transexuality is almost rare enough to meet the threshold rarity for genetic defects.

No one in science has previously suggested that transexuality can be adaptive under any circumstances; however Joan Roughgarden in her book Evolution’s Rainbow details many examples of other species with multiple genders, and reviews cases of transexuality in other cultures where it could be considered adaptive.

The origins of transexuality are still unclear also, and while it does seem more likely that transexuality is genetic than homosexuality, this has not yet been proven.

So now I’ve reviewed the possible explanations for evolution of same-sex sexualities and discounted them all, what is the alternative? How did LGBT people evolve?

One recent theory reviews homosexuality in males and females separately and suggests that male homosexual relationships provide the basis for social alliances and increased social status. Homosexuality in females provides bonds that lead to mutual assistance in raising children. These explanations for the evolution of homosexuality consider the state of the primitive social structures in which it may have evolved. For example in a social structure in which males and females were largely separate.

In these circumstances, the bonds between members of the same sex are equally or more important than bonds between members of the opposite sex. Homosexuality may have arisen as a way of forming stronger same-sex bonds.

This theory does not explain why heterosexuals exist however! The ratio of gay people to straight people can be explained by the obvious fact that alternative strategies of same sex bond forming exist that are equally effective in increasing Darwinian fitness.

If we compare the same-sex relationship strategies in use today, we can see that while straight people can bond in a number of ways, gay people form those bonds as well as sexual bonds. In this way we can see that all other things being equal, gay peoplehave advantage in forming social bonds over straight people. Gay people and straight people are therefore playing by different social rules and if those in control are straight, homophobia can be the result.

As more research is done on homosexuality, it is becoming increasingly clear that it evolved through a complex combination of genetics and environmental factors and that it is very obviously not some we can choose or not choose. Homosexuality is very likely, impossible to eliminate through genetic manipulation or homophobic actions and this has only really been realised in Western culture in the last 40 years or so. We are very lucky to live in a time and country that is realising the unjustifiable nature of homophobia and is acting to change laws and attitudes towards a society that views gay people as equal to straight people.

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