At a conference in February, geneticist Dean Hamer presented new findings about a region of the X chromosome that he’d claimed in 1993 was associated with male homosexuality. The concept of the “gay gene” continues to be bandied about in popular discussion as if it were an established fact.

Other scientists have been unable to replicate Hamer’s original findings, and his new claims have not yet been published in a peer-reviewed journal. Some social conservatives therefore deny that genes are relevant to same-sex attraction (SSA) at all. But such a denial goes beyond the available evidence about an open question, and it’s not necessary in the defence of traditional morals. Nor does consideration of biological factors in SSA preclude attention to the sort of family issues that can sometimes be helped by psychotherapy, as in my own life.

The thing is, our bodies matter – and not just in their outward shapes. Though we’re hardly determined by genes alone, environmental factors still have to have something to work on.

Biologist E. O. Wilson points out, “the same gene can produce different body types depending on environmental conditions. The classic case is the arrowleaf plant. If grown on dry ground, it produces an elephant-ear leaf; if grown in a pond, it puts up leaves like lily pads; and if grown in deeper water, it grows up with slender leaves like eelgrass.” Even identical twins could experience different environments, one of which triggered a particular gene to be expressed and one of which didn’t.

A key concept is that along with genes themselves, which transmit any information that is properly called genetic, there are epigenetic markers that influence how those genes are expressed during development. While epi-marks are usually new in each generation, it has recently been shown that they sometimes carry over between generations.

Based on this insight, the evolutionary biologist William Rice grabbed headlines in December 2012 by proposing a new explanation of how a tendency towards non-reproductive sexual behaviour could survive in a population. According to this model, there are sex-specific epi-marks that normally serve a protective function in the event of hormonal fluctuations in utero. But if these epi-marks are transmitted from fathers to daughters or mothers to sons, then they may cause expression of traits in the child that would typically be specific to the other sex. So, early in his fetal development a boy would acquire a tendency that in adulthood would incline him to seek male sexual partners. So goes the theory – which would, incidentally, appear to suggest that opposite-sex attraction is hard-wired into sexual maturation unless it is disturbed by these stray epi-marks.

Rice said his theoretical model could be proven within six months. He and his colleagues soon published a list of nine phenomena that ought to be observable if their model works. Disturbingly, the first of these proposed tests might use human embryonic stem cells, although an alternative technique was also suggested. In any event, nearly a year and a half later, no confirmation has yet been published.

Meanwhile there is considerable evidence that the early prenatal environment is implicated in two factors that have been associated with male SSA: men who are homosexually attracted are less likely than their opposite-sex-attracted counterparts to be moderately right-handed, and more likely to have a greater number of biological older brothers. But a finding that the latter factor moderates the effect of the former shows how subtle these interactions are.

Do these biological influences mean that “being gay is not a choice?” While our sexual attractions are very largely unchosen, we certainly have a choice whether to make them the centre of our identity. And whether to act on them.

Upon my return to Christianity in 1998 I completely re-evaluated my assumptions about homosexuality. After an extended period of Bible study and prayer, I settled on what a properly Christian position on homosexuality ought to say, and soon discovered that this and the Catechism of the Catholic Church matched exactly: a person with homosexual inclinations has intrinsic dignity, being made in the image of God, and must be accepted with “respect, compassion, and sensitivity” (CCC 2358); a homosexual inclination is “objectively disordered,” (CCC 2358) that is, disordered in what it points towards; but it’s not sinful to experience the desire; “Homosexual acts are intrinsically disordered… under no circumstances can they be approved” (CCC 2357).

This moral teaching will stand the test of time: nothing that scientists could discover about SSA need threaten such convictions.

Yet genetic research does bring risks. The Catechism condemns “unjust discrimination,” the ultimate form of which would be to eventually target and kill “gay fetuses.” Rightly do many people see potential “orientation-selective” abortion as abominable. As I recall, for this very reason I myself used to be wary of research into a biological basis of homosexuality and of the “born that way” argument for gay rights.

I don’t now doubt that some misguided parents would abort a “gay fetus” if a test became available. We must affirm that even if an unborn child is more likely to grow up with SSA, he or she can still lead a fulfilling and holy life. We should also challenge our progressive friends to consider what it implies about abortion in general for orientation-selective abortion to be wrong.

Alan Yoshioka, PhD, is an editor and writer whose business, AY’s Edit, specializes in medical research reports. Formerly a pioneering gay activist, he now speaks publicly with his wife, Theresa, about pastoral care for persons affected by same-sex attraction. Portions of this essay were previously published on their blog, The Sheepcat.