This is a summary of more than 20 years of research into homosexuality. It draws on more than 10,000 scientific papers and publications from all sides of the debate.
The research is orthodox, and objective, undertaken by a New Zealand scientist (PhD - Biochemistry) whose international career has spanned more than 40 years.
It is essentially a summary of our book, My Genes Made Me Do It! - Homosexuality and the Scientific Evidence (published USA, 2000, revised 2010, 2013, 2015, 2016 and kept current on this website.)
* SSA is shorthand for Same Sex Attraction, OSA for Opposite Sex Attraction
Those researchers who know most about genes and same sex attraction say ,“Your genes did not make you do it”. Bear in mind that many of the following arguments apply to all human behaviours.
These summary statements are much more deeply explored in each chapter.
The huge amount of change in sexual orientation is one of the clearest evidences that homosexuality is not hard-wired by genes or anything in the biological environment.
Large studies now show that:
These very complex comparisons of identical twins and non-identical twins definitively rule out genetic determinism. Identical twins with identical genes are about 11-14% concordant for SSA. If homosexuality were “genetic,” identical co-twins of homosexual men and women would also be homosexual 100% of the time. In classic twin studies the genetic fraction is less than 23% for men and 37% for women, and may be as low as 10%. Twin studies continue to find steadily lower genetic input into homosexuality as methodology improves and samples become larger. Everyone has at least a 10% genetic influence in their behaviour— because without genes there can be no human behaviour of any kind. Twin studies show that individualistic reactions to chance events (in which one identical twin reacts differently from the other) are by far the strongest contributors to homosexuality. In other words personal individual reactions to random events are a strong factor.
Genetic content of homosexuality is minimal
Geneticists, anthropologists, developmental psychologists, sociologists, endocrinologists, neuroscientists, medical researchers into gender, and twin study researchers are in broad agreement about the role of genetics in homosexuality. Genes don’t make you do it. There is no genetic determinism, and genetic influence at most is minor. Individualistic reactions to random factors are very important.
Those who say homosexuality is genetically influenced are correct, but only to about this degree:
If a girl becomes pregnant at age fifteen, we could argue that she is genetically predisposed to. We could say that in her culture, her genes gave her the kind of face and figure that send male hormones into orbit and bring her under a level of pressure that she is unable to resist. But that’s about the strength of the genetic influence. There are a huge number of environmental factors that could also have brought the pregnancy about, from cancellation of the basketball game she was going to watch with a girlfriend, permission to use Dad’s car, her boyfriend’s company, the movie they had just viewed together, and failure to use a contraceptive, to big environmental factors like personal values systems, peer group pressure, and an emotionally distant father.
Is this consensus likely to change? Might some major biological link be discovered which could change everything?
For most of these scientific disciplines, the findings have been clearly established from facts that will not change. But what of future studies of brain micro-structure, or detailed analysis of genetic composition and function? Will they reveal links between brain structure and human behaviours, or behaviours and genetic sequences?
Of course they will. Papers will continue to be published. But we can safely conclude that even authors wanting to find such links will almost always include the standard scientific caveats that the influence is minor, and that the environment is important. What we can reasonably say about future research is that it will enter new fields and come up with new links, but none of them will be definitive.
This is proved once and for all by studies of identical twins. They have identical genes, but if one is homosexual the identical brother or sister usually isn’t. There is only an 11-14% chance he/she is homosexual. This includes all the influences we know about now and those we know nothing about and have yet to discover. All of them, added together, only have a rather weak effect.
The first edition of My Genes Made Me Do It! in 2000 floated the trial balloon that the genetic content of SSA would ultimately turn out to be 10%. That is quite imprecise, and could be in the range 0-20%. But even if the final result is 20% this is a weak and indirect influence. At the time of writing, 2010, our assertion still holds, and is stronger than in 2000.
Homosexuality, as a genetic inevitability, has probably been gay activism’s most effective PR initiative in the campaign for equal rights and special protections. Although it is no longer politically correct or fashionable in many circles to say that homosexuals can change, it is scientifically accurate to say so. We are not speaking only of behavioural changes but changes in attraction.
The fact is that nothing makes us do anything—neither our genes nor our environment.
What is the cause of SSA?
There is no one cause. No single genetic, hormonal, social, or environmental factor is predominant. There are similar themes, e.g. childhood gender non-conformity, difficulties in developing a sense of gender identity (for a range of reasons), sexual abuse, peer and family dynamics, sexual history, but the mix varies with individuals, and individual personal responses to life-events are the single overriding factor. Two children from the same family and social environment can interpret the same incidents very differently. So random reaction, if it structures itself into self-image, can become a significant contributor to homosexuality — as twin studies show. Often, from early on, there is a felt inability to find acceptance in same-sex groups, often a defensive withdrawal from those groups in conflict with a desire to belong that can begin to intensify around some admired same-sex figure. After puberty that intense emotional focus can get confused with sexual feelings and activity, a response that, if the pattern continues for some years, can lead to self-identification as homosexual or lesbian and sometimes intentional adoption of a gay life-style. But each person is a unique combination of contributing factors and has a unique path out.
The homosexual orientation can and does change. The scientific literature is full of evicence of fluid sexuality. Where responses are deeply entrenched the process is longer. People who have not taken on the behaviour and lifestyle very deeply change more easily.
Is it all worth it? Those who take the process on will usually say it is, if they have had helpful input and support. In a therapeutic environment the sexual orientation of about two thirds of clients changes anywhere from slightly to profoundly. Others change greatly without any therapeutic input at all. Life itself brings along the ingredients for resolution of underlying issues. Half of all homossexual and bisexual people in the West become exclusively heterosexual over a lifetime. (Read more in Chapter 12 of My Genes Made Me Do It!) It may be heroic to "come out" to friends and family as gay, but it is even more heroic to swim against the tide and find a way back to what is still possible.
DNA is a ladder of nitrogenous bases and sugars that is a recipe for proteins, not sexual preferences. But it is also a ladder of destiny, a Jacob’s ladder, and it is our choice whether angels or demons walk up and down it. We can decide to capitulate to the “genetic argument” or not. Do your genes make you do it? You can choose.
I saw, struggling in a stagnant pool, a bee which had somehow fallen in. It flapped its wings futilely and tried to dog-paddle, but made no progress. It seemed to be drowning. All around the bee were little creatures called water-fleas who hopped round, trouble-free on the surface of the water. They didn’t seem interested in the bee at all. I took the bee out of the pool using a dead leaf from a tree, and set it down nearby on the slate surround. The bee staggered off the leaf, drunkenly wandering in its new freedom, headed straight back to the pool and fell in again. I lifted it out once more, and the bee staggered round rather aimlessly and seemed quite lost. I transferred it further away onto some grass. It tried to use its wings, but it looked to me as though they might be torn, and it might never fly again. It staggered from blade to blade, under some and over some in the three dimensional maze of the herbage. It even hopped from one blade to another, perhaps pathetically imagining it was flying. Then—suddenly—after I had practically given up, it flew! It wove a surprisingly straight course through the airy dimensions and was out of sight in seconds. I never saw it again. This I know: that bee reached heights the water-fleas couldn’t even dream of and so can you.