Previous article in this series: August 2020, p. 450.

For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life. II Corinthians 5:4

In the last article we considered the vast changes in morality that have swept Western society in the last half century or so. As a prime example of these sweeping changes, we considered how society’s view of homosexual behavior has rapidly shifted from the perspective of sin and shame to that of acceptance and normalization—even to the point of celebration. Though this massive shift in public opinion is certainly not the only indication of how completely Western culture has rejected the moral authority of Scripture and its sovereign Author, it does signal a level of perversity that God’s Word describes as man becoming his own idol (Rom. 1:21-25).

Because no man can escape the clear evidence of God in the creation as he slides toward self-idolatry, the justification of genetic determinism has been offered as a salve for the collective conscience of our generation. Over the past few years, we have been assured by scientists and cultural icons alike that people are just “born that way.”1 Although the prior article examined and criticized this idea, it left unexplained how the various fields of science have come to embrace the conclusion that human behavior, including sexual behavior, is controlled by genetics.

Here we provide an explanation of how these studies have been done and in the next article, Lord willing, we will discuss how their results may be correctly understood from a biblically Reformed perspective. This is necessary, both for us and our children, because the message of the world around us is aimed at capitulation to the moral corruption of our age. Rather than capitulating to secular explanations of scientific observations, we turn to God’s Word as our lens for interpreting science and understanding truth.

This is not an easy task, since the connection between genetics and behavior may very well be the most complicated question that modern science has tried to answer. That there is a connection is effectively undeniable, so the issue at hand is less about the veracity of the science and more about how we ought to understand and interpret it. As noted previously, our everyday experience seems to confirm that at least some aspects of behavior are inherited, that is, genetically encoded. Parents and children can have an almost uncanny behavioral resemblance to one another that is hard to explain simply by virtue of family life, especially when siblings from the same family are so different from one another. Putting hard scientific numbers on these everyday observations, however, turns out to be quite a challenge.

To get at the question of whether certain behaviors have a genetic component to them, scientists have turned to an approach known as an ‘association study,’ which provides statistics to evaluate whether two distinct things are related to one another. Genetic association studies seek to correlate a specific physical trait  that is displayed differently among humans (eye color, for instance) with variation in a specific gene or set of genes within the human genome. If a specific gene or set of genes correlates with a specific physical trait, it is reasonable to infer that these two things are causally related (that is, associated) to one another. This approach maintains that behaviors can be viewed as highly complex traits that might arise from the combination of genes that an individual receives from his or her parents.

For much of the twentieth century it was impossible to measure the variation in genetics between different people. While scientists were aware of how heredity worked and that there was a significant degree of genetic variation across the entire human population, there was no good way to obtain and analyze the entire genetic sequence of a human for use in association studies.2 Without this information, it is impossible to determine whether there is a relationship between a physical trait and genes—unless genetic similarities could be inferred without knowing the actual genetic sequences involved. This caveat is precisely the basis for association studies that use twins, because the genetic relationship between these individuals is known.

Due to the distinct cellular processes by which ‘twinning’ happens, fraternal and identical twins are genetically related in different ways. While fraternal twins are no more genetically related to one another than any other pair of siblings, identical twins are essentially genetic copies of one another. This means that any physical or behavioral trait that is genetically encoded should be shared equally by identical twins, but only in part by fraternal twins. The stronger this statistical correlation is, the more likely it is to indicate a genetic influence on a trait.

While a multitude of twin studies have been done for a broad variety of traits, the most comprehensive of them to study the role of genetics on behavior was initiated by researchers at the University of Minnesota in 1983.3 Among the more ingenious aspects of this study was to distinguish not only between fraternal and identical twins, but also to identify identical twin pairs who were raised by different families due to their being adopted after birth. The benefit of this practice is to dampen the influence of the home environment on individual development, which allows for similarities between identical twins to be attributed more to genetics than social influences. This ongoing study and others like it provide the initial basis for studying the role of genetics on behavior.

Over the past few decades, however, advances in genetic technology have opened the door to much more elaborate and specific studies of how genetics influence behavior. Rather than simply presenting statistical arguments about whether genetics must be involved— which is all that twin studies can really conclude— these studies have begun the task of associating complex traits with actual genetic sequences in the human genome. The tools in these genome-wide association studies (GWAS) primarily involve technologies that sample only the areas of variety in the human genome, though in recent years it has also become possible to obtain the entire genetic sequence of individuals in a relatively quick and cost-effective way.4 These technologies have enabled medical scientists to identify genetic risk factors for a host of diseases including cancer, heart disease, and neurological disorders, all of which can be more effectively managed or prevented before symptoms appear rather than after.

The advent of GWAS has also allowed genetic researchers in the field of psychology to begin pinpointing some of the genetic influences on behavior. Much of this work started with the evaluation of genetic influences on complex psychiatric disorders such as schizophrenia and depression, but has since extended into the realm of “normal” behaviors as well. This article makes no judgment as to whether this is wise or permissible from an ethical point of view—it may very well have been ill-advised to undertake many of these studies. Nonetheless, the studies were performed and we do have results from them. Sometimes these are disturbing and worrisome results for Christians who feel that the role of God in His own creation is slowly being eroded away in favor of the monolith of secular science.

This is especially true when secular scientists assume the authority to interpret their results in a way that contradicts the clear teaching of Scripture. And so we turn to the results of association studies that have specifically sought to relate homosexual behavior to genetics, which include both twin studies and GWAS.5 Results from twin studies have been around since the 1980s and correlate with broader movements to ‘destigmatize’ unbiblical sexual behavior that grew out of the social revolution of the 1960s “free love” movement. Many of these published twin studies are severely flawed and appear on their face to be driven by the bias of authors who designed them, so great caution should be exercised in accepting their results. Those few that are sufficiently large to permit legitimate statistical analysis and appear to be designed in an unbiased way, however, support a modest role for genetics in human sexual behavior.6

In parallel to the twin studies, several GWAS studies have been employed to address the same question of whether homosexual behavior has a genetic basis. Certainly the most famous of these was performed by a government scientist who managed to fund his search for a “gay gene” under the cloak of AIDS research in the early 1990s.7 While this study generated significant media coverage and was used heavily as propaganda by the homosexual community, attempts to replicate it have been inconsistent and increasingly disputed. A much larger study on genetic data and questionnaires from over a half million male participants, which was completed just last year, provides much stronger data to demonstrate that there is no such thing as a “gay gene.”8 Instead, the study concluded that there is only a weak effect of genetics on sexual preference that presumably results from the combined influence of many genes in concert.

Even at their best, these results are by no means a “smoking gun” for the idea that homosexuality—or anything apart from the divinely ordained pattern of human sexuality—is genetically determined in any absolute sense.9 But what of this ‘influence’ of genes? Assuming that the most recent scientific studies are correct in a formal sense, what are we to make of this genetic data as Christians?

For a long time, Christian activists have sought to fight the battle over homosexuality at the level of this article, which is in the field of scientific research and data analysis. While their intent might be laudable, we need to ask whether this strategy is really the one we ought to be concerned about. Although the most recent results noted above are gratifying in some sense, this is not where our faith ought to lie. Our help is in Jehovah, who made heaven and earth—and has spoken directly to us on these matters already.

In the next article in this series, we turn to God’s Word as a means to provide a framework of understanding. In that final article we will demonstrate that our inborn human ‘flesh’ (which includes our genes) may very well put sexual sins before us in a more acute way, but that our genes do not make us sin. This is scriptural truth, which has the final authority in this matter. 


1 This slogan is also the title of a popular book by William Wright, who purported to set the record straight regarding the “nature- versus-nurture” debate. The title provides ample insight into the author’s perspective, though whether his book is the source of the well-worn slogan is unclear.

2 This problem stimulated the international Human Genome Project and subsequent research to catalog the variety of genetic composition across the human race. While it is technically possible to obtain the entire genetic sequence—all 3 billion chemical letters— of a person today, the sheer size of information involved makes analysis amazingly complex and time-consuming.

3 At this point the ongoing study has registered more than 8,000 pairs of twins. The study functions primarily by “personality and interests tests…via mail.” More information can be found on the website for this study, https://mctfr.psych.umn.edu/research/ UM%20research.html.

4 All humans, regardless of race or ethnicity, represent members of a single species created by God and descended from Adam. All humans share 99.9% identical DNA sequences with one another, and therefore the proportion of genetic differences between any two individuals is at the very most only 0.1% (or 1/1,000th). Given the large size (about 3 billion chemical ‘letters’) of the human genome, however, that means that about 3 million of the ‘letters’ in the genome are variable among humanity as a whole.

5 The studies described here are largely summarized from the popular history of genetic research written by Siddhartha Mukherjee. While not at all comprehensive, the book presents a relatively dispassionate explanation of the studies relating behavior (including homosexuality) to genetics. Siddhartha Mukherjee, The Gene: An Intimate History (New York: Scribner, 2016). 370-390.

6 For example, the Swedish Twin Registry from 2008 used 2,320 identical twin pairs and concluded that genetics could at best account for 35% of sexual behavior in men and 18% in women. (Långström, et al. Archives of Sexual Behavior [2010], vol. 39, 75–80).

7 Mukherjee, The Gene, 374-375.

8 Ganna, et al. Science (2019), vol. 365.

9 The authors explain that while the total effect of genetics suggests a contribution of somewhere between 8-25%, even the very best genetic markers together can account for less than 1% of the variation between heterosexual and homosexual men. As such, the authors of the study have admitted it is “effectively impossible” to identify who is likely to be gay with any genetic test.