African scientists recognise that diverse sexuality is the norm

This article is part of a series The Conversation Africa is running on issues related to LGBTI in Africa. You can read the rest of the series here.

The Academy of Science in South Africa (ASSAf), in collaboration with the Uganda National Academy of Sciences, has just released a comprehensive “consensus report” on human sexual diversity.

This is a significant contribution in a continent in which gay relationships are criminalised in 38 out of 55 countries, four of which impose the death penalty.

The study used a panel of non-partisan volunteer experts to assess the considerable and often contradictory literature on biological, social and environmental factors in sexual diversity. It is one of the most clear-sighted evaluations that I have encountered, and it deserves to be taken very seriously in Africa and elsewhere.

A range of sexuality

The nub of the report is its conclusion that diversity in human sexuality is:

… a range of human variation, very little of which can justifiably be termed abnormal.

The source of this variation has been contentious for decades, despite the accumulating evidence that nature (“born gay”) is overwhelmingly more significant than nurture (“lifestyle choice”).

The report has a large and readable section on biological factors in homosexuality, including neurohormone effects on the fetus, and “epigenetic” influence on the activity of genes by chemical modifications that can be modified by the environment and are transmitted to all the cells of the individual, and sometimes even between generations.

As the report summarises, family studies over decades show that gay men are more likely than average to have gay brothers, and lesbian women more likely to have lesbian sisters.

Many twin studies showing that identical twins are twice as likely as non-identical twins to be concordant (both straight or both gay) imply a clear genetic component, but the 70% concordance leaves room for considerable non-genetic effect. This is true whether or not the twins were raised together.

A 1993 report of a gay gene on the X chromosome has been recently confirmed by a larger study, with the addition of another one or two gay genes.

To me, the most compelling argument that homosexuality is just one end of a normal spectrum is its prediction by evolutionary theory, which I have explored in detail previously.

Knowing about the wide variety of sexual behaviours in the animal kingdom, we can understand human sexuality in a broader context than our own society. It would be truly remarkable if humans had evolved without strong selection for mate choice genes.

Mate choice is one of the most highly selected traits in any animal. Just ask a fruitfly, which devotes a large share of its genes to choosing and attracting a mate.

Not gay genes, but male-loving variants

As I wrote previously, I think there will turn out to be many – maybe hundreds – of gay genes. But these should be considered “male-loving” variants of mate choice genes. In a female, a male-loving variant will induce her to mate earlier and have more children, making up for her gay brother. Makes sense.

I was happy to see in the report a discussion of data showing that the female relatives of gay males have more children than average women, thus preventing the gay gene from extincting itself.

There is so far no evidence for a “female-loving” variant that induces the brothers of lesbians to have more children, but it would be surprising if there weren’t many of them too.

We know of many “sexually antagonistic” genetic variants like this, which have opposite effects on the “genetic fitness” (that is, numbers of children) of males and females.

So, everyone has a grand mixture of male- and female-loving variants. This explains why there is such a broad spectrum of mate preference among both males and females.

It’s a bit like height, in which there are variants of many genes (estimates of more than 1000) predisposing to tall or short stature. Everyone – males and females – has a mixture. Some males and some females will be either very short or very tall, but most will be somewhere in the middle.

In the same way, I propose that there is a distribution from the very male-loving to the very female-loving among both males and females. Gays and lesbian people simply represent one extremes at one end of this distribution. Hypersexualised heterosexual males and females represent the other end.

Perhaps even more importantly, the report rejects the concepts that homosexuality is learned from, or results from behaviour of parents or peers, that it can rub off on others, and that it can be “treated”.

The report concludes that:

Contemporary science increasingly recognises the wide range of natural variation in human sexuality, sexual orientations and gender identities.

The report argues that it is important for countries to accept that sexual diversity is normal. There are severe consequences of persecuting and criminalising LGBTI, and not just directly for individuals and particular communities.

By persecuting, marginalising and criminalising whole sets of sexual behaviour, societies as a whole may quickly lose the public health battle against HIV-AIDS and other sexual health scourges, experience higher levels of social violence, and ignore other serious issues like violence against women and children.

Uganda’s Constitutional Court nullified an anti-homosexuality law in August 2014.Reuters/Edward Echwalu

The politics of homosexuality and role of science academies

It could be said that ASSAf has gone way beyond its scientific limitations by summarising its findings as:

Sexual diversity has always been part of a normal society and there is no justification for attempts to eliminate people who are not heterosexual from society. Efforts should rather be focused on countering the stigmatisation that creates hostile and violent environments.

Alternatively, this report may be criticised for not going far enough down the political path to removing criminal sanctions, stigma and persecution. However, every academy – including the Australian Academy of Science – must jealously guard its non-partisan reputation in order to be taken seriously.

ASSAf’s mandate is “to provide evidence-based science advice to government and other stakeholders on matters of critical national importance”. I believe ASSAf has done this. It is now up to other bodies to use the clearly stated scientific conclusions as a sharp-edged weapon to dispel myths and repel bigots.

It is often said that it is ineffective to fight illogical fears and hatreds with facts and logic, and it is sadly true that common sense and respect for data don’t always win out – think climate change and vaccination. But academies of science would risk their reputations, and mortgage their influence with governments of any persuasion, were they to go down the track of fighting irrational fear with emotive appeals.

Jenny Graves works at La Trobe University and is affiliated with the University of Canberra, ANU and the University of Melbourne. She has received funding from ARC and NHMRC. She is a Fellow and past office-bearer of the Australian Academy of Science.