Human sexuality: What does the science say?

What science can tell us about human sexuality is the subject of an important day conference being held in London on December 8, 2018. This event is likely to be of interest to anyone who would like to hear some of the country's leading experts explain what the most up-to-date science has been saying about sexuality and gender questions in the context of the current church debates.

Same-sex relationships are hotly debated in Christian circles – but are the arguments always well-informed? Reuters

Why does it matter what science says? It wasn't so long ago that society discriminated against left-handed people. Older readers may recall stories of children being slapped with a ruler for writing with their left hand or using their left hand to cut food. Historically the left hand was often associated with the Devil, and even our word 'sinister' comes from the Latin for 'left'.

Yet over the last few decades we have come to realise that left-handedness is not a reason for discrimination. We now accept that left-handed people are not inferior or less able, but are just different from the right-handed majority. And we have also discovered that there are good scientific reasons why some people are left-handed.

It might that there are some parallels with Christian attitudes towards sexual minorities. Perhaps we think that people who find themselves attracted to people of the same sex could get rid of their same sex desires if they tried seriously, or if they prayed or received counselling about it?

Perhaps we think that same-sex attraction is more a matter of nurture rather than nature. Maybe it is a consequence of inadequate parenting, for example a distant or unengaged father in the case gay men? Or that people sometimes develop same-sex desires because of an early sexual encounter with someone of the same sex? Or that cultures which do not promote homosexuality have far fewer gay or lesbian people than those which do?

We may not think of these ideas as scientific in nature. But in fact science has a lot to say about them, and it is important that we know what it says so that when we think about the ethics of same-sex relationships we are thinking in a way that is informed rather than uninformed.

For example, did you know that if you are a man, for each older brother you have your chance of being gay increases by 33 per cent? This is known as the 'fraternal birth-order effect', and has been found to obtain across different cultures. It only applies if you share a common birth mother with your older brothers, but not if you or they have been adopted or are step-brothers – which strongly suggests that the cause has something to do with the maternal womb environment.

Or did you know that there is a strong correlation between childhood gender nonconformity – boys behaving like girls or girls like boys – and later adult homosexual orientation? This nonconformity usually emerges by preschool age, long before children are sexually aware, in family environments where they have been conventionally socialised. This finding has also been reproduced in very different cultures from our own, and again it indicates that homosexuality may be more to do with 'nature' than 'nurture'.

Examples like these – and there are plenty of others – show that assumptions about homosexuality being due to people's upbringing or life experiences may need to be rethought.

Of course if people can change their sexual orientation, questions of whether it is a product of nature or nurture might be irrelevant.

But science is now shedding some light on whether conversion therapies, which seek to eliminate unwanted homosexual desires, are actually effective or not. The science here is complex, partly due to the lack of randomised, controlled trials – the 'gold standard' of scientific verification. Yet this does not mean that we know nothing about whether they work or not. More than that, we are beginning to get a sense of just how harmful they can be.

These are the kinds of questions that will be discussed at the conference. The speakers are among the most knowledgeable in the country on the subject, and include Prof Michael King (University College, London), Dr Qazi Rahman (Kings College London), Professor Peter Hegarty (University of Surrey), and Dr Stuart Lorimer (Gender Identity Clinic, London).

Seeking out the truth is an imperative for Christians: after all, we are followers of Jesus Christ, who is the Way, the Truth, and the Life. And science is one of the ways God has given us to understand the truth about the world.

Of course science can't dictate to us what we should think morally about same-sex relationships or questions of gender identity. Yet the church came to accept with Copernicus that the earth goes round the sun – this has rightly informed our interpretation of Scripture. Similarly learning what science has to say about sexuality and gender doesn't shortcut biblical and theological questions about how we should respond. But it may at least help dispel some of our misunderstandings.

Professor Robert Song teaches Christian ethics at Durham University. He will be speaking at the Faith, Science and Sexuality day conference at St John's Church, Waterloo, London, on December 8, 2018. Tickets cost £20 and are available at