Mention the word “homosexual” in any discussion after Sunday School and one will likely discover a wide range of responses and opinions. Indeed, few current issues have exercised the wisdom of the Church as homosexuality. To be sure, there are many reasons, including the fact that Christians have widely divergent viewpoints about homosexuality to the point that many persons seemingly are unable to engage in any meaningful discussion. At times the shouting has become so intense that emotion wins over graceful rhetoric and reasonableness. Nevertheless, we believe that any serious discussion of homosexuality requires an understanding of the possible causes of homosexuality.
When the biblical psalmist reflected on the mysteries of his life in Psalm 139, he echoed a question of humans everywhere: What makes us distinctively human-our bodies, our minds, our souls, or what? Nevertheless, with respect to basic biology and human reproduction, the Bible is largely silent. Today we understand a lot more about biology and reproduction, but the psalmist’s question still arises in similar forms. For example, where does our sexual identity, including our sexual orientation, come from-our genes, our environment, or our personal choices? As biologists, we believe that all of these-genes and development, environment, and choice-play a complex and integrative role in our development. Our opinion is that human sexual orientation has a considerable, but not a complete, genetic basis, and to regard it strictly as a personal choice or the result of only external environmental influences is to disregard current scientific research, some of which is outlined in this article.
Consider what these sexual minorities in our society have against them. They are told that a same-sex orientation is perverted or sinful, but with prayer and therapy they can join the sexual majority. Moreover, if God hates homosexuals, and if the Bible condemns homoerotic behavior with death, do not they deserve the opprobrium they receive? Should they not be damned for having an unacceptable orientation and lifestyle? Is not the AIDS epidemic a judgment by God on their sinful behavior?
Suppose, however, that our gay and lesbian friends and relatives have a sexual orientation not of their choosing. What then? Suppose they were born that way. Would our response then be different? Can an understanding of human biology help us in this quest for understanding? The aim of this inquiry thus is to examine what we know at the present time about the biological bases of same-sex attraction. Although some of the evidence remains controversial, we believe that the total weight of evidence suggests that, on the whole, same-sex attraction in animals, including humans, has a biological basis.
Science as a Way of Knowing
Any study of humans is fraught with many more difficulties than similarstudies of other animals. Obtaining a random sample of sufficient size can be difficult. Doing any forced experiments on people is unethical. Eliminating various biases in both the experimenter and the subject is nearly impossible. Nonetheless, during the late twentieth century considerable progress has been made toward understanding the nature, origin, and complexity of human sexuality. However, it is crucial to remember that certain experimental protocols are critical if the data are to have any degree of validity, and that any scientific study of human sexuality is by its nature difficult. Whatever one’s views are about the origins of same-sex orientation, all research should be scrutinized for the adequacy of all experimental and observational procedures.
Scientists work with ideas-lots of them. But how do scientists decide which of their ideas, sometimes called hypotheses, theories, or conjectures, are better than others? The answer is testability, the ability to find out by critical tests and observations whether or not an idea is reasonably correct. Some philosophers of science, such as Sir Karl Popper, insist that scientists can only disprove an idea, never prove it (Popper 1962, 1972). For example, consider the statement that all crows are black. This statement is true if and only if all crows have been observed and all are found to be black. In practice, however, to observe all living crows is probably impossible. Consequently, scientists study a sample of crows and then come to some sort of tentative conclusion about the color of crows. However, if a scientist discovers that one crow is white, then the statement that all crows are black is false and thereby has been disproved. In such cases, the original statement (hypothesis) must be modified, and, in the example just given, one could state that most crows are black.
In general, scientists dislike the word “prove,” a word best left for mathematicians and logicians. In any case, the work of a scientist is not easy. Scientists begin with a problem, often formulated as a hypothesis or conjecture, which is then investigated with a methodology suitable to solving the problem. Such investigations are usually not simple because, in general, good research must deal with a sufficient sample, an adequate control group, a clearly outlined experimental design, use of new techniques if applicable, possible use of sophisticated statistical tests, consideration of rival explanations, and peer review of results.
Moreover, scientists can investigate the natural world in several different ways. In some cases, the investigation proceeds by careful experimentation, often conducted within a laboratory with complex instrumentation. The methodology attempts to establish repeatable chains of cause and effect, and assumes a narrow and precise database often spelled out in clearly framed quantitative terms, as, for example, when investigating the role of vitamins in human health. In other cases, scientific investigations are best conducted by means of critical observations and comparisons, often involving complex and nonrepeatable events whose analysis leads to less precise formulation, as, for example, when scientists study relationships among fossils. With respect to our topic, any scientific study of the nature of human sexuality is by its nature difficult, especially in obtaining an adequate and unbiased sample. Thus, in careful studies of human sexuality, both critical observations and controlled experimentation may take place, and hence the total weight of the evidence becomes important, especially when suggesting new hypotheses.
On the other hand, some persons rely chiefly on anecdotes-stories assembled to bolster their case-for a given point of view. If many persons say that the earth is flat, well then, the earth is flat. However interesting anecdotal stories might be, they simply lack the rigor of a carefully planned scientific investigation. Unless a scientist follows careful and repeatable procedures, the research will carry little significance. For example, consider the following statements: 1) A homosexual orientation is chosen. 2) Hostile fathers “cause” their sons to become gay. 3) Gays and lesbians can be “cured” of their homosexual orientation, thus gays and lesbians can become heterosexuals. 4) Same-sex attraction has a heritable basis, and is fundamentally incurable. 5) 10 percent of the adult population is either gay or lesbian.
How does one rigorously test these hypotheses? Will anecdotes suffice? How many cases should one observe to underscore the probability that the hypothesis is acceptable and should be more rigorously tested to eliminate possible errors? Would counter examples disprove the hypothesis? If so, how many? How can one reach a reasonable conclusion about any of these hypotheses? Are there any examples of relevant experiments or carefully designed observations? In brief, if homosexuality has a biological basis, what evidence would we expect to find? How would we begin to test the hypothesis that indeed same-sex attraction has a biological component?
John Moore (1993) has referred to science as a way of knowing, and Ernst Mayr (1982) has considered biological thought as a growth, an ever-enlarging expansion of human knowledge about how the world works. Although as scientists it is our aim to understand the natural world, any in-depth understanding calls for years of training, use of sophisticated apparatus, and a community of critical investigators. It cannot be overemphasized: a community of fellow critics is as significant as years of training and observation. To be a good scientist requires all three.
Before we review some of the current research dealing with the biological bases of homosexuality, let us clarify a few definitions. In our usage, the term *biological*is an inclusive category. It includes heredity, i.e., our genetic makeup, the physiological *processes*involved in our development from a fertilized egg to an adult, and our environment. These are interacting components, and should be treated as part of an overall very complex system. In our view, it is impossible neatly to separate our heredity from our environment; both are important aspects in our growth and development (for more on this topic, see Seligman 1994, Plomin et al.1997, and Pattatucci 1998a).
As used here, “homosexual” is equivalent to the term “same-sex attraction,” i.e., “homosexual” refers to a person’s sexual orientation only, not to human behavior or practice. Too often the words “homosexual” and “homosexuality” are used loosely, and may refer both to one’s sexual orientation and to one’s behavioral practices. As Jack Drescher (1998b, 5) noted, “…being gay is not the same thing as being a ‘homosexual.’” For that reason, it is probably best not to use the word “homosexual,” unless the context is unambiguous. That said, however, we believe that the word “homosexual” (or “heterosexual”) is more than a label aiming to control other persons (Halwani 1998; see also Pattatucci 1998a, and T. S. Stein 1998). The label points to something real in the world of living things, and as scientists we believe this world exists independently of our observations, invented labels, and the like (for more on this, see Searle 1995, 1998). Our view is that same-sex attraction does occur in humans, no matter what name or label we give to describe this aspect of human behavior. However, there are other views about the purported human construction of reality that we experience, and the reader should be aware of the various views dealing with human interpretation and construction of reality as we know it (for an analysis of this issue, see DeLamater and Hyde 1998).
Percentages of Gays and Lesbians
As indicated above, in this booklet we are distinguishing sharply between one’s sexual orientation and one’s sexual practices. However, ascertaining one’s sexuality has never been easy. In fact some published research fails to indicate how gays and lesbians were ascertained (Fausto-Sterling 2000,10). Moreover, it is difficult to eliminate certain biases, such as those that might occur in determining whether a person is gay or lesbian or bisexual, and in choosing one’s sample for critical study. Current research in human sexuality is now addressing the problem of ascertainment bias (see Zucker and Bradley 1995, 131; Bailey and Dawood 1998; Bailey et al.1999).
Some researchers have developed a grid of key variables for determining a person’s sexual orientation. For example, Fritz Klein suggests “sexual attraction, sexual behavior, sexual fantasies, emotional preference, social preference, self-identification, hetero/homo lifestyle” as a grid (Fausto-Sterling 2000,10). Pattatucci (1998b), however, has suggested four variables for determining one’s sexuality-self-identification, sexual attraction, romantic or sexual fantasy, and sexual behavior. Nonetheless, determining nonheterosexual persons is not a simple matter, and in reviewing any research dealing with gays and lesbians, one should note how knowledge of the sexual orientation was obtained.
Determining rough percentages of gays and lesbians has not been easy either. Based on the widely cited studies by Kinsey and his colleagues a half century ago, 10 percent of the male (and female) adult population was considered more or less exclusively homosexual. However, as Mondimore (1996, 86) points out, the Kinsey data do not show such percentages at all, and thus the misuse of Kinsey’s data has resulted in a serious disservice to his research, however flawed statistically his research might have been. Moreover, Kinsey was measuring human sexual behavior only. He never classified humans on the basis of their sexual orientation.
Recent studies indicate that the ratio of gays to lesbians is roughly 2:1 (Pattatucci 1998b), and that bisexuality is relatively more common in women than men (who appear to be more bimodal, i.e., either gay or straight) (Pillard and Bailey 1998; Bailey et al. 2000; Bem 2000). Recent estimates suggest that 3 to 4 percent of men and 1 to 2 percent of women in the United States are virtually exclusively gay or lesbian. Comparative studies of other societies suggest roughly comparable figures (Diamond 1993; Dixson 1998, Table 6.2), although research by Sell et al. (1995) would place the percentages somewhat higher.
Possible Origins of Same-sex Attraction.
In a review at the end of a long and distinguished career, psychiatrist Judd Marmor (1998) assessed various current views of the causes (etiology) of homosexuality. He noted that homophobia-an irrational fear or dislike of gays and lesbians-in our society rests largely on lack of knowledge about gays and lesbians. Moreover, Marmor maintained that societal homophobia rests on four basic assumptions. According to these assumptions, homosexuality is: 1) sinful and/or immoral-an assumption largely based on religious grounds stemming out of the Judeo-Christian moral traditions, 2) unnatural, and thus basically unhealthy-a view sometimes based on the mistaken notion that in nature all species are inherently heterosexual, 3) a chosen behavior and therefore a behavior that can be “unchosen,” and 4) potentially contagious and thus can be acquired by seduction or bad role modeling.
Unfortunately, any or all of these mistaken views have been the basis for justifying discrimination against gays and lesbians in our society as well as differential treatment by psychotherapists (see Marmor 1998, for additional analysis). Marmor (1998) believed that understanding the possible causes of homosexuality does have a critical importance in how psychotherapists treat their patients. In any case, a better understanding of the origins of homosexuality should enable sensitive people everywhere to respect gays and lesbians as part of the significant variation among humans.
According to Marmor (1998), mental health professionals have suggested a number of explanations for the causes of homosexuality, including the following:
- An incomplete process of sexual development in which homosexuality thus represents a fixation occurring when the normal process of sexual development is arrested due to certain early life experiences, a belief based on Freud’s research. Marmor noted that psychoanalytic formulations arising from Freud’s work have been largely based on homosexuals in therapy.
- Homosexuals are narcissistic individuals.
- Male homosexuals dislike or even hate women because of “powerful unconscious negative feelings toward their mother figures.”
- Male homosexuals identify strongly with their mothers, which is why they become erotically attracted toward men.
- Male homosexuality is the “outcome of pre-oedipal problems of separation and individuation from the mother,” a view championed by Charles Socarides (1968).
- Homosexuality is “induced by a parental constellation of a close-binding, seductive mother and a distant, unloving father,” a view fostered by Bieber and his associates (Bieber et al. 1962).
As Marmor observed, all these “causes” can be found in heterosexual persons as well, and thus are not definitive characteristics of homosexual development (see Isay 1996, 3). Although dysfunctional parenting is often blamed for “causing” the development of homosexuality in children and youth, we have not yet been able to find any peer reviewed studies utilizing random samples demonstrating that dysfunctional parenting “causes” homosexuality. To date, there is some anecdotal evidence, but this is not the same as research involving careful sampling techniques and use of control groups. As Marmor (1998) noted, much of this sort of evidence represents the fallacy of psychological reductionism, in which a disturbed relationship is believed to be the cause of the variant behavior. LeVay, who has written about non-genetic factors and their possible role in human sexual development, states “[w]hat we know so far suggests that prenatal biological factors, including genetic factors in males, strongly influence sexual orientation. A role for postnatal environmental factors is possible but uncertain” (LeVay 2000a). For more on the role of dysfunctional parenting and reparative therapy see Nicolosi (1991) who advocates reparative therapy, and Drescher (1998a, b) who sharply criticizes this approach (see also Kandel 1999).
Marmor concluded that “[o]ver fifty variables in maternal, paternal and sibling family patterns have been found in male homosexuals-loving mothers, hostile mothers, loving fathers, hostile fathers, idealized fathers; sibling rivalries; intact homes; broken homes, absent mothers, absent fathers, etc.” Moreover, claiming that a loving father would preclude homosexual development in a son is simply not true, and as Marmor points out, he has treated a number of gays in therapy who have had a warm relationship with their fathers. Furthermore, careful studies of non-patient heterosexuals with non-patient homosexuals have shown “…no consistent relationship between the nature of the family constellation and subsequent sexual orientation” (Marmor 1998). What is ignored in these various psychoanalytic assumptions is that one’s personality structure may also have important biological bases.
Some Objections to a Biological Basis for Same-sex Attraction
Although we believe that biology has an important bearing on human sexual orientation, some persons believe that homosexuality has no biological basis whatsoever. This opinion is based on a number of widely held views, several of which we consider below:
The belief that no compelling scientific evidence or critical “scientific” proof for a biological basis of homosexuality has been demonstrated. This view is based in part on criticisms of apparent poor experimental procedures, inadequate sample sizes, sloppy experimental techniques, fudged data, experimenter bias, ascertainment bias, and the like (see Byne and Parsons 1993; Byne 1994, 1995, 1997; Terry 1997; for a critique of the critics of biological research, see Weinrich 1995).
The belief that people become oriented toward same-sex relationships due to various environmental causes, for example, bad nurturing by parents resulting in a disturbed early childhood relationship. Such beliefs in environmentalism are typically associated with claims of cures for one’s homosexuality. According to these views, same-sex orientation can be changed by using appropriate psychoanalytic and reparation therapies (Bieber et al. 1962; Socarides 1968, 1975; for a critique of these approaches see Haldeman 1996, and Stein 1996). For a discussion of why intellectuals in the United States became enamored with environmentalism (the view that human nature is quite pliable), the reader is directed to Seligman (1994, ch. 2). Read Colapinto (2000) for an example of environmentalism run amuck. Studies by Bailey et al. (1995), however, indicate that “any environmental influence of gay fathers on their sons’ sexual orientation is not large.”
The belief that people “choose” their sexual orientation, and are therefore morally responsible for this choice. Thus, if one chooses a same-sex orientation, one could as easily choose an other-sex orientation and is therefore morally responsible for doing so. As Bieber et al. stated (1962, 319), “heterosexuality is the biologic norm and that unless interfered with all individuals are heterosexual,” and furthermore, “a heterosexual shift is a possibility for all homosexuals who are strongly motivated to change.”
The belief that gays and lesbians are deviants (possibly demon possessed), and certainly not created that way. Consequently, these “perverts” must be cured, banned, or destroyed. This belief accords with the view that in the Bible a few scriptures suggest that homosexuality is a result of human sin and perversion and is therefore both pathological and evil. Hence, such persons must be reoriented (“cured”) or destroyed (see Lev. 18:22, 20:13).
The belief that homosexuality represents a pathology, perhaps a result of some sort of social disintegration. Such perversions indicate that homosexuals are deeply disturbed persons (Socarides 1975). Socarides believes this pathology is traceable to early childhood fears (i.e., preoedipal ones occurring before age three) and is therefore induced by dysfunctional family dynamics. Moreover, Socarides views same-sex orientation as a pathology that can be cured with proper psychoanalysis.
However, claims of cures of one’s sexual orientation must be regarded with some degree of suspicion (see Gonsiorek 1996; Haldeman 1996; Drescher 1998a, b; Marmor 1998). In this connection, we would ask how the relative degree of hetero/homosexuality was determined, whether or not the person believed he or she was bisexual, and whether or not the cure merely changed the pattern of behavior, not the basic same-sex attraction itself which is probably best judged by follow-up questions concerning the person’s fantasies.
Moreover, in contrast to these beliefs, our initial observation is that most gay persons knew they were different and that they were born that way (Isay 1989, 1996; White 1994, 200, 294; Kreider 1998; Patterson and D’Augelli 1998). Regardless, a crucial question for our Christian communities is how a person can become an “open” sexual minority (i.e., a GLBTI-a gay, lesbian, bisexual, transgendered, intersexual person) within a social climate that regards same-sex orientation as deviant and sinful and in which rampant homophobia is all too prevalent (Gillis 1998). Sadly, the suicide rates of gay and lesbian youth remain frighteningly high and account for perhaps 25 percent of all adolescent suicides. One study found that of 137 gay or bisexual boys, 30 percent had attempted suicide (Isay 1996,184, n.15; see also D’Augelli 1996, and Hartstein 1996).
According to Ellis (1996a), a belief that biology plays an important role in influencing sexual orientation fosters more tolerance and acceptance of gays and lesbians than if a person attributed same-sex orientation to personal choice or learned behavior.
In a landmark study, Evelyn Hooker (1958) asked the question whether gay men fit the typical stereotype often accorded gays: neurotic, shallow, uniformly disturbed persons. She then administered a series of psychological tests (Rorschach, Thematic Apperception Test) to both gay and straight men (30 each, but paired with respect to education, intelligence, and age) with the aim to discover the overall psychological health of either group. The test results were given to three eminent psychologists who were asked to judge, on the basis of the test results, which person was gay and which was straight. They simply could not tell any difference between gays/straights, and this failure marked a turning point among psychiatrists resulting in an eventual depathologizing of homosexuality (see Bayer 1987, for a history of this important change, and Cabaj and Stein 1996, for a modern psychiatric approach). Hooker concluded that, in terms of their overall mental health, homosexual persons are no different from heterosexual persons (see Mondimore 1996, 89, for a discussion of Hooker’s research). Nevertheless, Hooker’s study was summarily dismissed by Bieber et al. (1962) whose views have considerably influenced many subsequent workers in mental health (Gonsiorek 1996).
Review of the Biological Evidence for Same-sex Attraction
In the following discussion, we outline current evidence that human same-sex orientation has a biological basis. To be sure, none of the following research by itself may be sufficient to persuade anyone that same-sex attraction does have a biological basis. In 1983 only 16 percent of Americans believed that homosexuality was an inborn trait, but by 2000, 35 percent believed this to be the case (Bem 2000). The question remains, however, what causes same-sex attraction? Indeed, certain traits indicate a possible correlation, not a direct cause, and hence, as Daryl Bem (2000) suggests, we must avoid any “… premature rush to interpret correlation as causation.” As Jack Drescher (1998b, 46) stated, “the origins of human sexual attraction still remain an unsolved mystery.” Nonetheless, taken as a whole, we believe the evidence is compelling that underlying human sexual orientation there are biological aspects which must be taken into any account dealing with possible causative aspects of homosexuality (see also Dixson 1998, 165ff.). Excellent general reviews include those by Gladue (1993), Bailey (1995), Burr (1996), Bailey and Dawood (1998), Pattatucci (1998a), Pillard (1998), Pillard and Bailey (1998), and LeVay (2000a).
Richard Pillard claimed that “human sexual orientation has a ‘built-in’ quality. There seems,” he argues, “to be a fundamental bias toward either a heterosexual or a homosexual developmental path, prefigured early in life, neither taught nor learned, and profoundly resistant to modification. It exists recognizably in a variety of animal species and human cultures from diverse times and places” (Pillard 1997).
Moreover, there is an increasing opinion that the human phenotype (our appearance, constitution, etc., minus our genetic makeup) involves a complex interaction among our genetic codes, prenatal development, and postnatal environment. Given that roughly 3 to 5 percent of males and 1 to 2 percent of females have exclusively a same-sex orientation, is there any evidence for one or more genetic factors operating in the development of same-sex attraction (Sell et al. 1995; Michaels 1996)? Empirical evidence concerning the origins of sexual orientation generally focus on the nature-nurture controversies, and involve two broad approaches: 1) neurohormonal or neuroendocrine which suggests that “homosexual people have been subject to atypical levels of hormones in development, thus causing sex-atypical neural differentiation” (Bailey et al. 2000), and 2) behavioral genetics, which suggests that sexual orientation is familial, and if so, which portion is attributable to genetic, or to shared or nonshared environmental factors (Bailey et al. 2000; see also Wright 1998).
1. Pedigree studies (i.e., family histories). Pedigree studies examine family trees and thereby attempt to discover that certain traits also occur in one’s ancestors. With respect to the human sex chromosomes (X, Y), genes for certain traits occur in either the X chromosome or the Y chromosome. For some male homosexuals, a gene (or genes) may be located in the X chromosome and is thus inherited via the mother (males inherit their “X” chromosome from their mothers, their “Y” chromosome from their fathers). William Turner (1995) called such cases “Homosexuality, Type I.” By means of comparative genetic studies of a number of pedigrees, Turner’s research indicated that gene(s) for same-sex attraction of some homosexuals reside in the terminal region of the long arm of the X chromosome (denoted Xq28) (Turner 1995; see also Hamer et al. 1993, and Pattatucci 1998a, b). Moreover, both male and female homosexuality appears to run in families (Pillard and Weinrich 1986; Pattatucci and Hamer 1995a, b; Pillard 1996; Bailey et al. 1999; Dawood et al. 2000). Nevertheless, cross-gender familiality (i.e., families with an excess of both gay brothers and lesbian sisters) requires more investigation, although “powerful evidence exists that homosexuality runs in families, and no evidence contradicts it” (Pillard 1996).
Recruiting subjects for any statistically significant research has been difficult, although with better sampling methods and more sophisticated analyses, a more compelling analysis appears to be emerging (see Bailey et al. 1999; Kirk et al. 2000). Although stated percentages of nonheterosexuals (i.e., gays and lesbians) vary, Pattatucci (1998b) claims that in her research (with Dean Hamer), the nonheterosexual base lines for men are roughly twice that for women. Let us repeat: doing careful research of this sort involving humans is not easy-good sampling methods, lots of money, and sufficient numbers of willing subjects are absolutely necessary (for a pertinent review of some difficulties in undertaking family and pedigree studies dealing with sexual orientation, see Bailey et al. 1999).
2. Twin studies. Identical twins are generally twice as likely to share a same-sex attraction as fraternal (nonidentical) twins (52 percent to 22 percent in one study-Bailey and Pillard 1991; see also Whitam et al. 1993; Turner 1995; Dixson 1998, 166; for a revised downward estimate, see Bailey et al. 2000). Turner’s work also discussed the problem with discordant identical twins, one of whom is heterosexual, the other, homosexual, and he noted there are biological reasons why identical twins are not always concordant for the trait under investigation (Turner 1994, 1995). Critics sometimes charge that, because of this discordance, same-sex attraction cannot be genetic, but Turner convincingly explains why these differences might occur and the reader is directed to his papers for additional study (Turner 1994, 1995). In a recent comprehensive study involving a large (N = 4901) cohort of twins in Australia, Kirk et al. (2000) found “statistically significant support for the existence of significant genetic contributions to the trait of homosexuality.” This study, along with that of Bailey et al. (2000) supports the view that both genetic and environmental variables are components of homosexuality, and that the genetic component is almost certainly due to more than one gene.
In recent twin/adoptee studies, about half of the heritability in sexual orientation appears attributable to a genetic component, with most of the rest attributable to an unshared environment (i.e., different friends, experiences, relationships to parents and other persons, illnesses, etc.) (Bouchard and McGue 1990). However, identical twins, whether raised together or raised apart, showed about the same outcome (Pillard 1996, 1997). As already indicated, some studies show that, given one twin with a same-sex orientation, the other twin will have a similar sexual orientation in roughly 50 percent of both male and female identical twins, but with lower rates in fraternal twins (males: 22 percent, females: 16 percent) and non-twin siblings (males: 9 percent; females: 14 percent) (Baron 1993; for a different estimate, see Bailey et al. 2000). These data suggest a strong genetic contribution to same-sex orientation, although “the precise nature of these factors [has] yet to be understood” (Whitam et al. 1993). Moreover, unlike male fraternal twins and non-twin brothers in these studies, female fraternal twins showed little percentage difference from fraternal non-twin sisters. These apparent differences between gay and lesbian fraternal twins and fraternal siblings remain unclear, but Seligman (1994, 156, 281) suggests that important differences in fetal hormones may be involved. To date, however, we lack critical research into the overall biology of same-sex attraction between females.
Cross-fostering studies aiming to learn whether sexual orientation can be attributable to either the biological or the foster parent (hence, the biological: genetic; the foster: environmental) have yet to be done for sexual orientation. Such studies, however, are expensive, complex, and beset with problems arising from generally small sample sizes (Pillard 1996).
3. Molecular biology of the gene. Research by Dean Hamer and his colleagues suggested that male homosexuality might be a heritable trait (Hamer et al. 1993; Hu 1995; Pattatucci and Hamer 1995a). Following a rather complicated investigation involving the techniques of molecular biology, Hamer claimed that possibly a gene (or genes) was located in the terminal part of the long arm (section) of the X chromosome (the so-called Xq28 region). Hamer, however, never claimed that a gay gene (or genes) was actually located in the X chromosome, only that there was a strong probability that some heritable component (gene or genes) occurred in the X chromosome, which, in males, is inherited from their mothers. Hamer’s work has been criticized by Byne (1995), Byne and Parsons (1993), and Rice et al. (1999), although Hamer has responded to an earlier report in 1995 by Rice (Hamer and Copeland 1998, 197). Rice and his colleagues have attempted to replicate Hamer’s research, but the extent to which they were able to do this is not clear. Had they actually replicated Hamer’s research, they would have utilized Hamer’s original samples, but this assumes that Hamer’s blood samples would have been available for duplicating the research. To the best of our knowledge, Rice and his colleagues attempted to replicate Hamer’s research by means of a different set of persons (see also Zucker and Bradley 1995, 134).
In an important, but often overlooked paper, William Turner (1995) claimed that what he called “Homosexuality, Type I” is determined by a gene in the terminal region of the long arm of the X chromosome (the Xq28 region-same region as suggested by Hamer et al. 1993). As indicated above, Turner based his conclusions on evidence derived from his pedigree studies, including finding a larger number of homosexual relatives in the maternal lineage as compared to the paternal lineage, higher rates of certain medical problems on the maternal side (spontaneous abortions, miscarriages, stillbirths, etc.), and a “distorted sex ratio in the maternal generation bearing male and female homosexuals” (maternal aunts greatly outnumber maternal uncles, possibly a result of semi-lethal genes) (see also studies by Bailey and Pillard 1991).
Although Turner’s work supports Hamer’s research, Bailey et al. (1999) suggest that “X-linked genes account for relatively few cases of male homosexuality,” and that a fairly large sample will be required to detect such a gene(s). Their study “found no evidence that male sexual orientation is influenced by an X-linked gene, [but their results] are not strong evidence against X-linkage” (Bailey et al. 1999; see also Bailey et al. 2000). Clearly, additional studies on family pedigrees should be undertaken, but these are difficult and subject to various degrees of cooperation on the part of the families investigated. Thus the search for a clearly identifiable gene or genes for male homosexuality continues (Pillard 1997). Since there are thousands of genes (estimates vary from around 40,000 to 100,000) involved in human development and functions, it appears unlikely that complex characteristics such as sexual orientation would result from the action of a single gene.
Yet as Pillard states, “[i]nteresting environmental influences, presumably substantial in any behavior trait, are unknown for sexual orientation and difficult to study since the relevant influences may be active early in life while the outcome, a defined sexual orientation, may not appear for decades” (Pillard 1997). “We would like to emphasize,” Pattatucci and Hamer (1995b) write, “that sexual orientation is complex. It is probably the result of numerous genetic, physiological, and environmental factors interacting together. Therefore, it is our view that no single factor, be it genetic, physiological, or environmental, determines a given person’s sexual orientation. Rather we believe that certain factors may contribute to the overall development of an individual’s sexual orientation.”
Whatever the genetic influence may be, it undoubtedly plays a subtle role along with various developmental and environmental factors. There is no question in Richard Pillard’s mind, however, that the “genetic analysis of behavior is a powerful tool to advance our understanding of sexual orientation” (Pillard 1996). “The eventual payoff,” Pillard (1996) continues, “will be to link genes, brain function, psychological development, and human social organization in a multilevel understanding of human sexuality. Various sexual orientations should become a comprehensible part of nature rather than a deviation or perversion of it. To understand the diversity of life is gratefully to recognize our dependence on that diversity.”
4. Brain anatomical studies. Recent studies dealing with brain differences between heterosexual and homosexual men showed several interesting differences. The interstitial nucleus of the anterior hypothalamus (INAH3), located more or less in the center of the brain, is two to three times larger in straight men than in gay men (LeVay 1991, 1993, 1996, 2000a). LeVay’s study is highly suggestive that hormones and fetal brain development may be interrelated, and that the interstitial nuclei of the anterior hypothalamus (INAH3) of gay men were more like those of heterosexual females than heterosexual males. What causes this difference, and whether the INAH3 determines one’s sexual orientation, is not known.
Moreover, other studies of the brain involving the anterior commissure (Allen and Gorski 1992), and the suprachiasmatic nucleus (Swaab and Hofman 1990) also showed structural differences between gay and straight men. Although we are not at present certain how these differences arose, certain hormonal processes seem to be involved. For example, experimental studies more than forty years ago at the University of Kansas showed that manipulating the levels of testosterone during fetal development of guinea pigs and rats could influence the sexual behavior of the adult. These manipulations also affected the size as well as the structural characteristics of the sexually dimorphic nucleus (SDN) in the brain (see LeVay 2000a). As Bailey and his colleagues (1999) state, “[t]he most influential biologic theory of sexual orientation is that male homosexuality results from incomplete masculinization of relevant brain structures during prenatal development.”
However, the origins of female homosexuality remain obscure (Bailey et al. 1999, 2000; Bem 2000). Recent studies show that, when compared with women, gay men are often more consistent in that their orientation, attraction, fantasy, and behavior are all directed toward other males. Sexual orientation and attraction in women apparently vary more, and relatively more women than men are bisexual-men just seem more hardwired in their sexual orientation than women (Hamer and Copeland 1998, 184ff.).
Recently, William Byne, an earlier outspoken critic of LeVay’s work, has reinvestigated LeVay’s research by examining a new set of brain samples (LeVay 2000b). Byne found that the INAH3 indeed does exist, that the cause of death (AIDS, etc.) does not affect its size, and that, although Byne found that the size differential between gay and straight men is not as large as that reported by LeVay in his 1991 paper, nevertheless, the INAH3 is larger in straight men than in the gay men in Byne’s sample. Byne also discovered that, although the number of nerve cells in gay and straight men are the same, such differences as do occur arise later in fetal development. What causes this difference is not known at present. As LeVay remarked, “[w]hat’s surprising about the gay/straight difference in INAH3, then, is simply that it is so localized and obvious, rather than being diffusely spread through the synaptic architectures [i.e., nerve cell connections] of the entire brain. This offers the hope that we will eventually be able to understand the origins of sexual orientation at a cellular level” (LeVay 2000b).
5. Developmental hormone differences in humans. Typically, an individual with XX sex chromosomes develops into a female, and an individual with XY sex chromosomes develops into a male. However, according to Fausto-Sterling (2000, 53), perhaps as many as 1.7 percent of all human births are intersexes of one type or another. This means that not all persons are sharply delimited males/females, a fact too often ignored in discussions of human sexuality.
For example, some children with XX chromosomes are born with enlarged adrenal glands. In such individuals, during the later part of fetal development, the adrenal gland secretes large amounts of male sex hormones, thus these persons become masculinized females (Dixson 1998, 285). On the other hand, some XY children are born with highly feminized genitalia due to being non-responsive to the masculinizing hormones, and thus develop psychosexually as women (Dixson 1998, 288). Both of these are generically inherited traits, and often such individuals become homosexuals in later life, thus underscoring a possible biological (and genetic) basis for same-sex attraction (Dittmann et al. 1992; Zucker and Bradley 1995, 146; Ellis 1996b; Savin-Williams and Cohen 1996; Pattatucci 1998b; LeVay 2000a).
There is some evidence that the greater number of older brothers a man has, the possibility increases that such an individual will develop a same-sex attraction. However, the number of older sisters apparently has no effect on sexual orientation. Whether this points to some maternal immune reactions to male fetuses is not clear, but the hypothesis does suggest some interesting lines for further studies (Dixson 1998, 167).
6. Childhood gender nonconformity. Careful studies of young children show that young boys with highly feminine traits (such boys are often known as sissies) frequently become males in later life with a same-sex attraction (Pillard and Bailey 1998; Bailey et al. 2000; Bem 2000; Dawood et al. 2000; Kirk et al. 2000). These childhood gender nonconformity differences typically show up in a child’s life long before any sexual awareness occurs. Different roles associated with gender include “… participation in aggressive activities, rough-and-tumble play, and competitive athletics, toy preferences, imagined roles and careers, cross-dressing, preference for same- or opposite-sex playmates, gender identity, and social reputation as ‘sissy’ or ‘tomboy.’ The group differences are generally larger for men (gay versus straight) than for women (lesbian versus straight)” (LeVay 2000a).
Daryl Bem (2000) has proposed an interesting theory (Exotic-Becomes-Erotic or EBE), which suggests that “individuals can become erotically attracted to a class of individuals from whom they felt different during childhood.” Thus whatever the biological basis for same-sex attraction might be, the causation is not direct, but is mediated instead by gender nonconformist factors (see Bailey et al. 2000 for some support for this hypothesis). Moreover, Bem (2000) suggests that “childhood gender conformity or nonconformity [is…] the only significant childhood predictor of later sexual orientation for both men and women.” In fact, one study (cited in Bem 2000) concluded that roughly seventy percent of both men and women reported that “they had felt different from their same-sex peers during childhood.” There is some evidence that these gender nonconformist traits may be linked to different male hormone levels during fetal development (Berenbaum and Hines 1992; Berenbaum and Snyder 1995; LeVay 2000a). As LeVay stated, “[g]ay people frequently experience anti-gay discrimination for years before they realize that they are in fact gay” (LeVay 2000a). For more on this important topic, see Rottnek (1999), a book of essays discussing childhood experiences of both males and females.
7. Throwing skills. When comparing accuracy in throwing a ball to a target, straight men usually did better than straight women, a difference already exhibited in young children. However, gay men performed about as well as straight women, but much worse than straight men, a difference possibly the result of different patterns involving neuronal connections developed in the brain due to variations of male hormonal levels (Hall and Kimura 1995; LeVay 2000a).
8. Fingerprint ridge differences (dermatoglyphy). Studies of discordant identical twins (one gay, one straight) show that the number of fingerprint ridges are left-shifted (i.e., there are more ridges on the left hand than on the right hand) in the gay twin as compared with the straight brother. Because fingerprint ridges are determined in the second trimester of pregnancy, such differences have a biological basis. The reasons for these differences remain unknown, but they cannot be due to post-natal environmental factors (Hall and Kimura 1994; LeVay 2000a; for a review of the possible importance of fingerprint patterns, see Zucker and Bradley 1995, 185).
9. Otoacoustic emissions. Levels of weak sounds produced by the inner ear during the process of transforming incoming external sounds into electric signals appear to be different between men and women. The relative strength of the emissions appears to be correlated with testosterone levels such that the higher the level of testosterone the weaker the signal, with men having generally weaker signals than women. However, in lesbians and bisexual women, the signals appear to be significantly weaker when compared to heterosexual women. These differences also appear to be correlated with the differing levels of male hormones during fetal development (McFadden and Pasanen 1999; LeVay 2000a).
10. Anthropological data. Following extensive field work in the United States, Guatemala, Brazil, and the Philippines, Whitam and Zent (1984) concluded there is strong evidence that “… early cross-gender behavior may appear in all societies, and is consistent with later adult sexual orientation” (see also Diamond 1993). Furthermore, many of these societies have institutionalized gender-discordant behavior (Dixson 1998, 164; Murray 2000). Moreover, Whitam and Zent (1984) believed that the “…pattern of the distant and hostile father…is the result of strong negative sanctions toward homosexuality in the Anglo-Saxon world, [and is] not the cause of homosexuality.”
11. Domesticated animals: Gay ram studies. In her doctoral study at the University of California at Davis, Anne Perkins found that of 2100 rams she studied, about 10 percent have a same-sex attraction. Sheepherders knew for a long time that not all rams were equally interested in mating with ewes-those rams that were not were dubbed “dud studs.” As Perkins and Fitzgerald (1997) state, “(w)hat is unique and special about rams as a research animal is that variations in sexual expression occur without human intervention. Domestic rams are the first animals to be used for studying both physiological and social correlates to sexual orientation occurring naturally within a population.”
Perkins observed that after repeated exposure to females, sexually inactive rams (about 16 percent) may remain inactive, may become a low sexual performer, or may be exclusively male-oriented (about 10 percent). Thus, the basic biological question is to uncover what factors are correlated with ram sexual performance. Ram sexual behavior and reproduction are quite complex and are “mediated through sensory, perceptual, endocrine, neural, and social systems,” which are “under the influence of both genetic and environmental controls.” Ram genes thus “work indirectly via physiological systems.” Perkins found that the brain structures capable of sensing potential mates differ between heterosexual rams and homosexual/nonsexual rams, and that in heterosexual rams the activity level of aromatase (an enzyme in the medial preoptic area) is twice that found in homosexual rams. Moreover, in homosexual rams and ewes the estrogen receptor levels in the amygdala (small brain structure necessary for integrating sensory information underlying ram sexual behavior) are about 25 percent that of heterosexual rams. Furthermore, Perkins noted that homosexual rams do not convert to heterosexual rams; they copulate only with other rams.
Perkins concluded her study with this cautionary note: “human sexuality is far more complicated than sex in nonhuman species. Yet, we hold much in common with other mammals. We must not dismiss the notion that genes initiating physiological processes may greatly influence our choice of mates as well” (Perkins and Fitzgerald 1997). However, it is clear from Perkins’ study that some rams are attracted only to other males, and that this orientation is rooted in the biology of the animal. There are gay sheep and they remain that way, despite all attempts at cures.
12. Natural history of animals. One might properly ask whether any same-sex orientation and behavior occur naturally in animals. As Simon LeVay (1996) states, this question “has been debated for centuries, most often in the context of efforts to stigmatize homosexuality,” and there have been answers: none, few (but it is bestial), many (those that do are unclean). However, recent studies of animal behavior reveal that same-sex attraction is hardly uncommon. In fact, as Helen Fisher (1992, 167) claims, “homosexuality is so common in [nonhuman] species-and it occurs in such a variety of circumstances-that human homosexuality is striking not in its prevalence but in its rarity.”
In a monumental work on animal homosexuality, Bruce Bagemihl (1999, 12) states that “[h]omosexual behavior occurs in more than 450 different kinds of animals worldwide, and is found in every major geographic region and every major animal group.” Moreover, based on known in-depth studies of animal sexuality, Bagemihl (1999, 31) estimates that 15 to 30 percent of all animal species likely would reveal homosexual behavior. Bagemihl thus lays to rest the view that animals are always strictly heterosexual, and in fact claims that “in many cases homosexual pairings, particularly companionships, actually exceed heterosexual ones in their stability and duration” (Bagemihl 1999, 23). Animals and humans are not so different after all, whatever moral conclusions one might draw from this observation. However, animal ethologists have observed that “animals with ‘different’ sexualities and/or genders are completely integrated into the social fabric of the species, eliciting little of the attention, hostility, segregation, or secrecy that we are accustomed to associating with homosexuality in our society” (Bagemihl 1999, 54).
Consequently, whatever one may think of human homoerotic practices, it cannot be stated that they are “against” nature because only humans supposedly engage in same-sex erotic practices. According to Bagemihl (1999), a partial list of animals with homoerotic behavior includes various primates (including bonobos, who share more than 98 percent of their genes with humans), dolphins, whales, seals, deer, giraffes, buffalo, goats, zebras, wild pigs, elephants, lions, foxes, bears, kangaroos, squirrels, bats, geese, ducks, herons, gulls, swallows, warblers, finches, bluebirds, sparrows, crows, ostriches, penguins, hummingbirds, woodpeckers, various reptiles and amphibians, fish, many insects, spiders, and various domesticated animals (see also LeVay 1996, 197ff., ch. 6; Wilson 1978, ch. 6; Fisher 1992, 166ff.; for research on homosexuality in Drosophila melanogaster, see Pattatucci and Hamer 1995a).
These ethological studies of animal behavior show two important facts: no (or very little) homophobia among animals occurs, and same-sex attractions and behavior are simply not “against nature.” As Bagemihl (1999, 59) states, “the vast majority of other creatures have an approach to sexual and gender variance that is decidedly humane, rather than human-and they might even offer us models of how our societies could integrate differently oriented or ambiguously gendered individuals into the fabric of social life.” Both Perkins’ study and Bagemihl’s review illustrate that same-sex attraction is not confined to humans, nor can it be said to be unnatural, whatever moral lessons one extrapolates from these examples (see also McKnight 1997, and Dixson 1998, 146ff.). In a word, nature is prolific, diverse, and not easily subject to human classification.
Some Broad Observations
As Simon LeVay remarked, “[g]enes and prenatal factors have only so much to say about our sexuality: there still could be some role for parenting, for life experiences or even for that bugaboo of many gay activists-choice” (LeVay 2000c). In an arresting summary, psychiatrist Richard Pillard (1998) maintained that “[i]n the end, it may turn out that even the most exact knowledge of sexual orientation development will give us no more than a guess about the outcome in a particular individual. There is now evidence that neural connections in the brain are imprecisely directed. As neurons in a fetus sprout and grow, there appears to be only a statistical chance of their hooking up at an exact destination. Thus, it seems plausible that we may never be able to predict, even knowing the specific genes, the particular family circumstances, and the cultural milieu, what will be the sexual orientation of a specific individual. The outcome for any particular person may always be, in some measure, a matter of chance” (italics ours). And Alan Dixson (1998, 314) agrees: “At this time we are far from understanding all the factors which govern the development of gender identity and sexual orientation in human beings. In the current state of knowledge it would…be premature to conclude that a single developmental pathway leads to homosexuality.”
Finally, Pattatucci (1998b) points out that “[a]lthough investigating genetic sources of variation in sexual orientation is a crucial endeavor for understanding the role of families, perhaps the most exciting frontier for family research lies in studying nonshared environmental sources of variation.” Children are often very different, even within the same family, but the question is why. Why does one child become a gay or lesbian and another child a heterosexual adult? Increasingly, it is now apparent that the nonshared environment, such as different friends, sports interests, food and clothing tastes, hobbies, etc., as experienced by children, is a far more important influence in a child’s life than the shared environment such as going to the same church, living at the same address, etc. Disentangling these components (genetic factors, shared and nonshared environments) is complicated, but constitutes important directions for future research (for more on this, see Pattatucci 1998b, and Bailey et al. 2000).
Implications for the Christian Community
Persons with same-sex attractions are very much a part of the church. The question now exercising Christian communities is how to respond to our GLBTIs-our gay, lesbian, bisexual, transgendered and intersexed sisters and brothers. Without exploring fully this question, this study points the way toward a more humane view with respect to our sexuality. First, we suggest that we respect the self-identity of nonheterosexuals. When such persons claim they were born gay or lesbian, we should respect their views. Second, we should cease from claiming that same-sex attraction in itself is pathological or evil, that gays and lesbians should seek some sort of cure, and then marry a person of the opposite sex. As Lawrence Hartman noted, we have seen a shift in how same-sex orientation has been regarded: “from sin, to crime, to illness, to difference. The difference has many mental health aspects…[b]ut the conceptual shift from sin to crime to illness to difference is large” (Hartman 1996,. xxxi).
If our review has any merit, it should give us extreme pause before we hunt for dubious alternative explanations why people are gay or lesbian. Our acceptance of nonheterosexuals should never be based on their attempts to find a workable cure of their orientation (see Drescher 1998 a, b). To be sure, much research needs to be done, especially in establishing clear genetic links to human sexuality, whatever its variation, as well as investigating the role of the nonshared environment in the psychobiological development of persons within a family. Still, the direction of any future research should not dictate how we respond to the mandate from Jesus to love all persons. The Body of Christ will always be remarkably diverse.
Where to From Here?
Many contemporary scientists conclude that human sexual orientation is a complex mix of factors, all of which contribute to a mature development of human sexuality: genetic, hormonal and developmental, psychological, and social. Both genetic and nongenetic factors have important roles, but the exact identity of these nongenetic factors remains uncertain. Yet they probably include various random processes in prenatal development, possible parental relationships, and early sexual experiences (LeVay 1996, 273ff.). Moreover, same-sex orientation appears to be “linked with a broader collection of sex-atypical characteristics,” e.g., many mental traits, brain structures, lateralization of brain function, and dermatoglyphic (skin) patterns, and thus combines a mosaic of various male/female traits (LeVay 1996, 275). Human sexuality includes both a set of behaviors (what we do), and a specific orientation (who we are). As Richard Pillard (1997) remarked, “human sexual orientation has a ‘built-in’ quality. There may be a fundamental bias toward either a heterosexual or a homosexual developmental path, prefigured early in life, neither taught or learned, and profoundly resistant to modification.” This is our view also.
In his magisterial book, The Spirit and Forms of Love, Daniel Day Williams (1968) charges the church with its lack of teaching concerning the “meaning of sexuality in human existence,” and he goes on to state that this “deficiency…in the area of sex is analogous to the theological reaction to the development of scientific knowledge” (Williams 1968, 218). Without question, our knowledge of the cosmos has come largely from secular auspices, with far too little contribution from the religious establishment. Understanding human sexuality in its various dimensions requires a concerted effort involving discoveries in anthropology, psychology, biology, psychiatry, human history, and theology.
Furthermore, we need to develop a Christian sexual ethic if our lives are to become a “creative aspect of the life of agape, the giving of each person in service to God and [one’s] neighbor” (Williams 1968, 235). We believe that in this community of love, a same-sex orientation belongs to the goodness of creation. Indeed, we can recognize our sexuality as a sacrament, and this recognition extends to all persons. Yet “coming out” is often an intensely painful experience for GLBTIs (Glaser 1998). However, it is our hope that the homophobia too often viciously expressed among Christians will be regarded as an evil that simply has no place in the Kingdom of God. Our lives are to be agents of God’s grace to other persons, including the GLBTIs among us.
It is our hope that this essay will contribute to a better understanding that human sexuality has important biological aspects and that these differences can be regarded as a normal variation among humans. We believe that as Christians we have a moral obligation to give our youth the best possible information about human sexuality. If we can celebrate our sexuality in all its dimensions as a gift from God, we can move a long way toward experiencing the depth and richness of agape that the body of Christ requires for its wholeness and well-being. The real test for any denomination is whether we can accept gay and lesbian teenagers and adults into the life of our churches. Can we claim to preach the Good News if we do anything less? Can we claim to be peacemakers if we do anything less?
On the basis of the evidence presented in this chapter, we conclude that same-sex attraction does have a biological basis. This does not mean, however, that one’s environment has no role in influencing our sexual development. But explaining human sexuality is far too complicated for it to be reduced to easy formulations and patterns. Whatever the “cause” of a person’s sexuality, what one does in response to one’s sexuality and sexual attraction is a matter of human choice. But as for the attraction itself, it appears that, for most persons, this is beyond their immediate control. Consequently, we believe that one of the initial steps in understanding same-sex attraction is to examine what is known about the biological bases of homosexuality.
Furthermore, the call to the Christian community is to find enlightened ways to help persons with a same-sex attraction accept themselves as they are, and to discover ways to find fellowship and companionship within a Christian community. As psychoanalyst Richard Isay suggests (1996, 175), “[o]pposing discrimination in a prejudiced society is good for the psyche. It directs anger away from ourselves to where it rightfully belongs. But it is love that makes us know who we are. And let no individual, no organization, and no institution try to take that away!”
The following persons commented on various drafts of this chapter, but all remaining opinions and statements are entirely our responsibility. Special thanks are due to Joe Blowers, Willis Breckbill, Thomas Chamness, Ted Grimsrud, Philip Hertzler, Dorothy Keener, Gladys Keener, Lois Kenagy, Willard Krabill, M.D., Norman Kraus, Roberta Kreider, Barbara Longenecker, Charles Longenecker, Ruth Conrad Liechty, John A. Lapp, Jay Martin, Dorothy Yoder Nyce, Elsie Steelberg, M.D., and Joyce Thompson.
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