Before we turn to the specifically human data and to the evidence for biological factors (nature) and sociological factors (nurture) in the formation of homosexual orientation, it will be worthwhile to define sexual orientation.

The UK Government uses the figures of 5-7% as their guide for the proportion of gay, lesbian, and bisexual people within the population. This is an informed estimate. There is no conclusive data. Surveys that directly ask this information are understood to give a base-level figure as some individuals will, for instance, deny their orientation as they believe their feelings to be morally wrong.

Homosexuality was considered for many years to be a disorder or illness. The American Psychological Association (APA) classified it as such in their internationally respected Diagnostic and Statistical Manual of Mental Disorders (DSM). However, in 1973 following more extensive research this classification was removed from its list of diagnoses and disorders.[1] In 1994 the APA went further by stating “…homosexuality is neither a mental illness nor a moral depravity. It is the way a portion of the population expresses human love and sexuality.”[2]

What is sexual orientation? At its most obvious level, sexual orientation can be described as the direction of one’s sexuality. Professor Simon Rosser gives a vivid description:

“Imagine you’re walking down the street and you see somebody attractive to you. Immediately inside you say, ‘Wow! That’s a gorgeous person.’ It seems to happen even without thinking – it’s something way deep within us: something automatic or pre-conscious. I like to describe it as the ‘Wow’ in life. It would be a very sad thing if everyone walked down the street and didn’t find anyone attractive. It would be a sadder, more impoverished world.”[3]

These attractions are instinctual. It is not a matter of choice.

The classical natural law argument uses the notion of procreation, and the obvious complementarity between male and female for conceiving children, to determine that a homosexual act, which cannot be procreative, is against nature and thereby a denial of the will of God, the Creator. However, many sexual acts performed by heterosexual couples do not and cannot result in procreation.

What also of couples who are unable to have children as one of them is infertile, or men who have had a vasectomy (‘the snip’), or women who have had tubal ligation (‘tubes tied’) or a hysterectomy.

Furthermore, the argument from procreation roots the concept of sex between two people at the level of physical acts (the creation of children) and tends to dismiss the relational aspects of sex – the bond that it helps build between two loving people:

“to many Christians, if there is a God-given purpose of sex, it is to be found rather in the possibilities it offers for expressing and building love between the partners, so that what we need is not a narrowly focused theory about sexual acts, but rather reflection on the role sex plays in the life of people, their development, and their love.”[4]

The Kinsey Scale, devised after the work of Alfred Kinsey from the late 1930s onwards[5], places everyone on a continuum from exclusively heterosexual orientation to exclusively homosexual. An individual person may have a sexual orientation at any point on that scale.

Despite that continuum, three classifiers are frequently used to simplify classification:

• Heterosexual or straight orientation: an exclusively heterosexual individual will only have “Wow!” experiences for members of the opposite sex.
• Bisexual orientation: those with a bisexual orientation will experience the “Wow!” moment when seeing a man as often as when they see a woman. Others may tend to be attracted more often to women, others to men – as you would expect if orientation exists on a continuum.
• Homosexual or gay and lesbian orientation: an exclusively homosexual individual will only feel “Wow!” towards people of the same sex.

The majority of the population falls at the heterosexual or straight end of the continuum. However, significant numbers of people, albeit small minorities in comparison to the heterosexual population, are spread across the rest of the spectrum with a gay, lesbian or bisexual orientation.

There is another classifier that should be mentioned, those people who are transgender. This is not a different orientation, however. Rather, this refers to people who have a gender identity different from their physical identity.[6] They may feel that their identity is that of a man, but their body is that of a female, or vice versa.

It is also worth mentioning that while the Genesis account says unambiguously that God created them ‘male and female’[7], our current understanding is more subtle. There are a significant number of children born as ‘intersex’. This means that the child’s reproductive or sexual anatomy does not fit as typically male or female. There are many different conditions that can result in an child being born intersex. The frequency is hard to determine as a result, but specialists are called in to help determine a child’s sex at approximately 1 in 1500 to 1 in 2000 births.[8]