Is there scientific evidence that a person is born a homosexual? If so, then how can they be held responsible for the Bible condemning homosexuality? Let’s take a look at the scientific evidence and then put it up against what the Bible teaches.
Are Homosexuals Genetically Predisposed to be One?
There have been many scientific studies that tried to show that homosexuals are predisposed or born into homosexuality but there remains no conclusive proof that a person is born with a gay or lesbian gene. A variety of studies have been undertaken to try and pin down whether there are hormonal, environmental or genetic influences, but researchers have been unable to find that one, single cause for a person’s sexual orientation. In a specific study that compared non-homosexual men and homosexual men, a large variety of data was studied including biological information, environmental, and even physical measurements. The conclusion of the available data was that there are no reliable predictors of a person’s sexual orientation. 
Clinical psychologist, Dr. Stanton Jones, says that if genetics play a role it is a very small roll, saying, “The scientific evidence doesn’t support it.” In Dr. Stanton’s book, “Ex-Gays? A Longitudinal Study of Religiously Mediated Change in Sexual Orientation,” he concluded that gay men have been and can be converted towards heterosexuality. Even if there were a homosexual gene that triggered a person’s tendency to be homosexual, are we not all predisposed to being sinners anyway? We must come out of our sin, repent, and confess, and as we are all in Adam and all will die, we are to also be in Christ and be made alive (2 Cor 15:22). Every one is born into a sinful state but we are not to remain in that state (Psalm 51:1). We are all sinners (1 John 1:8, 10) but we must all confess our sins and repent of them, no matter what sin  it is (1 John 1:9). Being “born this way” is no excuse because we are not helpless victims of our genes.
Repentance and Faith
Let’s say that a person had parents that drank to excess. That was my case. I was somewhat predisposed to drink but I can not use that as an excuse and just throw up my hands and give in to it and say, “Well, I just can’t help it. I was born with a genetic predisposition to be an alcoholic.” We are all sinners and we must all repent (turn around and away from sin). Mankind is fallen. We are all genetically flawed and predisposed to sin but if a person lies and say that, “Well, it just runs in the family,” they say that they are just helpless victims of their own genes. Nothing could be further from the truth. There may be some exceptions for alcoholics and drug abusers but it can‘t be an excuse for us to be drunks or drug abusers. Alcoholics and drug abusers may pick up on their parents lifestyle more than just being helpless victims of their genes.
The Bible on Homosexuality
What does God say about the homosexual lifestyle? Does He “understand” about a person saying that they are born that way? I have been counseling a man who is living with his girlfriend and they have already had a baby. He concluded that since God put this love in his heart for his girlfriend that He would understand. That since they don’t believe in marriage  they can live with each other and not feel that they are sinning. He said, “Surely God knows that I love her and that He must understand that.” In reality, this man is creating a false god or making a god in his own image and that is sin. God never condones sin and will not just look the other way. As Paul said about idolatry, “I see that in every way you are very religious. For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: to an unknown god. So you are ignorant of the very thing you worship—and this is what I am going to proclaim to you” (Act 17:22-23), and “in the past God overlooked such ignorance, but now he commands all people everywhere to repent. For he has set a day when he will judge the world with justice by the man he has appointed” (Acts 17:30-31).
So, does God “understand” when we live in sin, including homosexuality? Absolutely not! Paul is clear on this point when he wrote, “do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. And such were some of you” (1 Corinthians 6:9-11). The difference here is what Paul said, “And such where some of you.” This means that they were doing these things but not anymore. They had repented of these things and even though they might fall back into it at times, just as we all do in sin (Romans 7), they don’t stay there. They repent, get back up, confess their sin, and strive to live holy, godly lives.
This article is not condemning homosexuality. It is also showing that the man who was living with his girlfriend and saying “God would understand” is living a life of sexual immorality and such who refuse to repent will not be in the Kingdom of Heaven, anymore than unrepentant thieves, idolaters, drunkards, or swindlers will. The person who believes that God would understand is really saying that God will compromise on sin and He absolutely will not. They are idolaters because they are making a god in their own image.
There is no sin that can not be forgiven (1 John 1:9). We are all sinners (1 John 1:8, 10). A person can still feel same-sex urges and be saved. Just as I was at one time a drug abuser, I still have those urges to do them again. I loved beer too but I drank to drunkenness and so today I have decided to not drink anything at all alcoholic to prevent myself from “falling off the wagon” again. I could find no valid scientific evidence that there is a “gay gene” or “lesbian gene” anymore than there is one for a person who steals, lies, or cheats. Sin is sin  but a person who is still tempted to have a homosexual relationship is not sinning as long as they don’t actually have that same-sex relationship.
Remember that Jesus was tempted just as we are, but without sin. The writer of Hebrews states that “we do not have a high priest who is unable to sympathize with our weaknesses, but we have one who has been tempted in every way, just as we are–yet was without sin” (Hebrews 4:12). He was tempted in His humanity just as we all are today so Christ understands our temptations, but temptation is not sin. That is why “he had to be made like his brothers in every way, in order that he might become a merciful and faithful high priest in service to God, and that he might make atonement for the sins of the people” (Hebrews 2:17). This is because Jesus “himself likewise partook of the same things” (Hebrews 2:14). This is why “he had to be made like his brothers in every respect” so that He understands what our temptations are like (Hebrews 2:17). The only difference is that He never sinned and so, “For our sake he [God] made him to be sin who knew no sin, so that in him we might become the righteousness of God” (2 Corinthians 5:21).
Homosexuals who are not practicing this lifestyle and trying to overcome it should be welcomed by churches and not condemned for Christians can not cast the first stone unless it would be at their own selves. The same could be said of former drug abusers who are still tempted (like me), like former prisoners, alcoholics, and so on. The churches would be empty if we eliminated everyone who has sinned.
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Resource – New International Version Bible, The Holy Bible, New International Version®, NIV® Copyright© 1973, 1978, 1984, 2011 by Biblca, Inc.™ Used by permission. All rights reserved worldwide.  Rice, G., C. Anderson, N. Risch, and G. Ebers. Science. 1999 Apr 23;284(5414):665-7. Male Homosexuality: Absence of Linkage to Microsatellite Markers at Xq28.