Based on the complexities and controversies of this subject, it would seem to be more appropriate to have books written by scholars and intellectuals who are well equipped to deal with this topic in depth rather than writing about it in a blog.
However, there may be some fundamentals that can be established as a framework for a bit of edification and discussion. Here goes.
Probably there have always been gay and certainly straight members of the human species. According to the National Geographic’s Genographic Project all living human beings are descended from one common African ancestor who lived about 140,000 years ago. (The Project leaders have nick-named this common ancestor “Adam.”) They claim all human beings alive today are descended from this “Adam” and we can all be traced back to his DNA. (Current differences in race and nationalities are attributable to a long period of mutations or genetic markers which have occurred throughout the many generations since “Adam.”) So it would be safe to assume gays appeared well before the time of “Sodom and Gomorrah.” However, based on the estimated number of gays as opposed to the number of straights, gays would appear to be anomalies in Nature.
According to the Williams Institute at UCLA School of Law which is considered a sexual orientation think tank, their April 2011 research report estimates that 1.7 percent of American adults are gay. Quoting from their website, “The Williams Institute is dedicated to conducting rigorous, independent research on sexual orientation and gender identity law and public policy. A national think tank at UCLA Law, The Williams Institute produces high-quality research with real-world relevance and disseminates it to judges, legislators, policymakers, media and the public.”
Let us assume then that about 1.7 percent of American adults are gay or homosexual while another 1.8 percent according to the same April 2011 report may be bi-sexual, etc. The result is that the overwhelming number of adult Americans is straight or heterosexual. This is obviously in accordance with Nature since men and women are sexually compatible while homosexuals are not. The force of Nature is to have each species in existence to reproduce with the goal of transmitting DNA from one generation to another.
Therefore are gay inclinations uncommon in that these acts are against what seems to be this force of Nature? Further, is homosexuality something that is inborn or genetic? Dr. Francis S. Collins is one of the world’s leading scientist/geneticist and head of mapping the human genome. In his book entitled, The Language of God, published in 2006, he states that sexual orientation is genetically influenced but not hardwired by DNA, and whatever genes are involved represent predispositions not predeterminations. (See page 260 of the aforementioned book.)
So the scientific DNA evidence is saying there may be tendencies of attraction of some toward those of the same sex but free choice remains in play. It would seem homosexual behavior is probably something chosen by an individual and not something absolutely preordained.
Now why would some relatively small number of individuals choose to follow the gay life style? Clearly, men and women were made for each other based on the complementary of anatomies. Not to desire one of the opposite sex upon which human nature is based is a sign of brokenness – something that inhibits attraction to the opposite sex. For example, there always remains the interplay of Nature and Nurture which influences all of humanity to a significant degree. As such all humans are flawed to some extent and we see the consequences of these defects in our daily news headlines and in our own lives.
According to the Judeo Christian tradition all homosexual acts are gravely evil as well as other serious sins such as covetousness, malice, envy, murder, strife, deceit, slander, ruthlessness, etc. In the Christian tradition sin is the consequence of not worshipping the Creator who is evident from His Creation.
Taking the passage from the book of Romans, chapter 1, verses 18-32 which best describes this condition you can readily see the consequences of rejecting the revelation of God in Nature. This passage from Romans is shown below in its entirety, using the NIV translation:
18 The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness,
19 since what may be known about God is plain to them, because God has made it plain to them.
20 For since the creation of the world God’s invisible qualities–his eternal power and divine nature–have been clearly seen, being understood from what has been made, so that men are without excuse.
21 For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened.
22 Although they claimed to be wise, they became fools
23 and exchanged the glory of the immortal God for images made to look like mortal man and birds and animals and reptiles.
24 Therefore God gave them over in the sinful desires of their hearts to sexual impurity for the degrading of their bodies with one another.
25 They exchanged the truth of God for a lie, and worshiped and served created things rather than the Creator–who is forever praised. Amen.
26 Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones.
27 In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion.
28 Furthermore, since they did not think it worthwhile to retain the knowledge of God, he gave them over to a depraved mind, to do what ought not to be done.
29 They have become filled with every kind of wickedness, evil, greed and depravity. They are full of envy, murder, strife, deceit and malice. They are gossips,
30 slanderers, God-haters, insolent, arrogant and boastful; they invent ways of doing evil; they disobey their parents;
31 they are senseless, faithless, heartless, ruthless.
32 Although they know God’s righteous decree that those who do such things deserve death, they not only continue to do these very things but also approve of those who practice them.
This rejection of God leads to a darkening of the mind causing dishonorable passions. By stubbornly refusing to worship the Creator our minds eventually prefer to remain in this state of darkness. Thus, all manner of sin results and this passage from Romans lists the these sins such as homosexuality as well as covetousness, malice, envy, murder, strife, deceit, slander, ruthlessness, etc. In effect all sin is caused by rejecting God and worshipping creatures, especially oneself.
So, just as we all have a common ancestor called “Adam,” gays and straights both have a predisposition to sin. This tendency is not predetermined by our DNA since one must opt to sin. By truly worshiping our Creator we are given a choice to reject all manner of sin. This is truly in our DNA.
PS: Consider this quote from Pope St. John Paul II:
The human person, made in the image and likeness of God, can hardly be adequately described by a reductionist reference to his or her sexual orientation. Every one living on the face of the earth has personal problems and difficulties, but challenges to growth, strengths, talents and gifts as well. Today, the Church provides a badly needed context for the care of the human person when she refuses to consider the person as a “heterosexual” or a “homosexual” and insists that every person has a fundamental Identity: the creature of God, and by grace, his child and heir to eternal life.