Tag Archives: gene

by

Did God Create Biodiversity via Genetic Engineering and Climate Control?

See the source image

Did God Create Biodiversity via Genetic Engineering and Climate Control?

James R. Aist

Then God said…–Genesis 1:11, 20-26

The theory of evolution is a materialistic concept to explain biological diversity. It is comprised of two basic components: 1) the enormous body of valid, scientific evidence related to how biodiversity may have came about; and 2) the assumption that this “evolution data set” can only be explained by random, natural forces and processes inherent in the material world. This assumption is based largely upon the initial assumption that a creator (God) does not exist. However, it is not sound, objective, scientific protocol to begin an investigation by eliminating one of two tenable and competing theories based on a mere assumption. That is what we call “junk science”, and it is not really science – the objective search for truth – at all. The so-called “science” of evolution is a prime example of how a body of valid scientific information – the evolution data set – can be misused to give the impression that a mere assumption (e.g., that a Creator God does not exist) is actually proven fact.

In this article, I explore alternate, viable scenarios that can explain the evolution data set by invoking the involvement of an “intelligent designer”, otherwise known as God. As you read further, please keep in mind that the God of the Bible is sovereign over all of creation, knowing the end from the beginning (Isaiah 46:9-11) and, therefore, He knew from the beginning where He intended to take biological diversity, as well as all of the intermediate steps and processes He was going to use to take it there. For a fuller background on these proposed scenarios, click HERE.

The evolution data set and “divine genetic engineering”

The first intelligent design scenario I want to discuss begins with the acknowledgement that a valid evolution data set does exist and that the God of the Bible is no dummy. Don’t you suppose that when God set about creating biological diversity, He would be smart enough to not “reinvent the wheel”, so to speak, every time He wanted to create a new “kind” or a new “species?” Would He not start with a creature He had already made and genetically modify it to make the new one? So then, of course, at the morphological, anatomical, genetic and biochemical levels, the closely “related”, but different, newly created form would have considerable commonality with the form from which it was derived, having been “genetically engineered” by God Himself. And that’s exactly what the evolution data set may be showing us, minus any atheistic assumptions. What I’m saying here is that the same body of evidence that is used to support the materialistic theory of evolution can just as easily be seen to support the theory of “intelligent design” by way of “divine genetic engineering”, if one does not begin with the assumption that an intelligent designer does not exist. This scenario would involve intelligent design from start to finish, and it would look to us just like materialistic evolution.

Random mutations, natural selection, survival of the fittest, and “divine climate control”

In the previous section, I presented a “genetic engineering” scenario for the direct involvement of God in the creation of the spectacular biological diversity we see in the world around us. In this section, I will present a scenario for an intelligent designer working indirectly to guide or direct the evolutionary process. The materialistic theory of evolution involves, at its most fundamental level, random mutation (natural, molecular modification) of genes, a resultant sub-population of organisms carrying mutated genes that are beneficial, and selective survival of the organisms that are carrying the beneficial gene(s) because they are best adapted (most fit) for the existing or impending environmental conditions that develop naturally from time to time. Over millions of years, such a process, repeated over and over again, is believed to have produced new species and “kinds” (e.g., dogs, cats, horses, fish, reptiles, grass, trees, seaweed, etc.) of animals and plants. It is assumed that this process occurred “naturally”, without the influence of an intelligent designer. But wait a minute, who is it that controls the climatic conditions that drive natural selection and result in survival of the fittest? The God of the Bible is sovereign over all of His creation (Genesis 1:1-27; Isaiah 46:9-11; Revelation 19:6). It is He who placed the moon and the stars in the heavens and maintains them in their respective orbits (Genesis 1:14). He caused the earth to pause in it’s rotation for a full day, giving the impression that the sun had stood still (Joshua 10:12-13). He commands the wind and the waves, and they obey (Exodus 14:21; Mark 4:39), and He calls forth drought to scorch the land (Haggai 1:11), and it is dry. And, it is He who sends the rain as He pleases (Genesis 7:4, 11-12; Matthew 5:45). The relevant conclusion here is that the God of the Bible is sovereign over (i.e., in control of) the so-called “natural” climate changes that evolutionary theory credits with driving the “natural selection” process leading to the appearance of new species and kinds and the extinction of others through “survival of the fittest.” Thus, by exerting “divine climate control” again and again over millions of years, God could have steered what we refer to as “evolution” in any direction He desired, thus controlling and directing both the extinction of old species and kinds and the development of new species and kinds, using the very mechanisms of random mutations, “natural” selection and survival of the fittest that are so fundamental to the materialistic theory of evolution. This scenario also would involve intelligent design from start to finish, and it would look to us just like materialistic evolution. Thus, the same evolution data set used by evolutionists to support the popular theory of materialistic evolution, could just as well be seen as validating this “divine climate control” mechanism of evolution.

Conclusions

There are at least three alternate and viable scenarios for the involvement of intelligent design (God) in the development of the vast biodiversity present on planet earth. One scenario has God, by a process of “divine genetic engineering”, directly modifying genes in a previous creature to produce a closely related and similar new creature. Another scenario has God indirectly causing both the extinction of existing creatures and the proliferation of new creatures by exerting “divine climate control” to drive the evolutionary process by way of “natural selection” and “survival of the fittest.” A third scenario would be a combination of the first two scenarios, in which God “genetically engineers” the genome of a species or “kind” and then exercises “divine climate control” to give the new creature a competitive edge going forward. This may be the most likely scenario, because it would probably be a more effective and efficient way for God to satisfy and manifest His spectacular creative drive as recorded in Genesis 1:11, 20-26. All of these scenarios would involve intelligent design from start to finish, and they would look to us just like materialistic evolution. Many students of biodiversity reject the unnecessary, atheistic assumptions of the materialistic theory of evolution and believe that theistic mechanisms offer better, more objective, explanations of biodiversity than does the more popular materialistic mechanism.

Recommended reading

If you want to read further and deeper into these and related matters, I strongly recommend the following book: Geisler, N. and F. Turek. 2004. I Don’t Have Enough Faith to Be an Atheist. Crossway, Wheat, IL. 447 pp.

(To read more of my articles on biblical topics, click HERE)

by

Born-Gay Hoaxes “Outed” by Real Science!

See the source image

Born-Gay Hoaxes “Outed” by Real Science!

 James R. Aist

“You cannot prove a point by appealing to an assumption. Proof requires objective evidence.”

Since the early 1970s, homosexual people have increasingly claimed that they were “born gay” and that, therefore, they could not change even if they wanted to. By repeating this claim over and over again for decades now, gay activists have managed to win over a large percentage of heterosexual “believers” to their cause, without any substantial basis in fact to validate the claim that they were “born that way.” And yet, this hoax remains deeply ingrained in our culture at all levels. Therefore, it is necessary to re-examine carefully the scientific and other documentable facts concerning the origins and development of homosexuality to see if there is any truth at all to the “born gay” claim and its spawn, the “immutability” claim. The critical questions are 1) is homosexuality already determined at birth by biological factors and 2) is homosexuality, immutable (unchangeable). We now have several recent research and review articles to help us to arrive, once again, at the correct answers to these questions.

Is Homosexuality Already Determined at Birth by Biological Factors?

By far, the most powerful and reliable way to test the claim that homosexuals are born gay is to conduct scientific studies on data taken from large “twin registries.” The data in these large data bases are obtained randomly with little or no sample bias and are relatively representative of twins in the general population. In twin studies, the “concordance” answers the simple question, “Where one twin of an identical pair is homosexual, what percentage of co-twins is also homosexual?” The concordance of the twin pairs is a measure of the level of influence of biological factors (generally assumed to be the genetic influence) on whatever trait is being studied, in this case, homosexuality. If homosexuals are born gay, then whenever one twin of an identical pair is homosexual, the co-twin will also be homosexual, giving a concordance value of ~ 100%, indicating a very strong, determinant genetic influence. A concordance value of ~ 20%-30%, on the other hand, would indicate a weak, non-determinant influence of genetics.

The reader is referred to Aist, 2012 (click HERE), Diamond and Rosky, 2016 (click HERE) and Whitehead and Whitehead, 2012 (click HERE) for more extensive reviews of the pertinent scientific literature on twin studies. The recent study by Zietsch, et al., 2012 (click HERE) can be used to illustrate representative research results obtained with large samples from twin registries. They used a very large sample (9,884) of twins from the Australian Twin Registry, one of the largest samples to date for twin studies of homosexuality. In this sample, there were 1,840 identical twin pairs (1,133 female and 707 male). Their calculated value of 24% concordance for homosexuality indicates a weak genetic influence. Moreover, their calculated figure of 31% for heritability of homosexuality also indicates a weak genetic component. This leaves around 68% of the variance in the data set represented by post-natal, “shared environment” and “residual” environmental influences combined.

That brings us to the conclusion that homosexuality is not already determined at birth by biological factors (e.g., genetics). Simply put, these results not only do not provide scientific evidence to support the “born gay” claim, they provide definitive and conclusive, scientific proof that “born gay” is, in fact, a hoax. Real science has “outed” the born-gay hoax.

Is homosexuality immutable (unchangeable)?

The claim that homosexuality cannot change is a direct extension of the claim that homosexuals are born gay, and, as we have seen above, “born gay” is, itself, a total hoax. Nevertheless, it is possible to evaluate this claim scientifically on its own merit. Previously, several authors have assembled extensive and persuasive evidence to show that sexual orientation, including homosexual orientation, is not fixed, but is, instead, amazingly fluid (Aist, 2012, click HERE; Sorba, 2007, click HERE; and Whitehead and Whitehead, 2016, click HERE). A new and comprehensive review article written by two supporters of so-called “gay rights”, Diamond and Rosky (click HERE), focuses on four relatively new scientific studies that demonstrate conclusively that homosexuality is, in fact, a fluid trait. These studies all used large data bases that followed the self-identified sexual orientation of individual subjects over long periods of time. Such “longitudinal” studies are the only way that the fluidity of sexual orientation in a representative sample of people can be documented and quantified. All four of these studies gave similar results regarding the considerable fluidity of sexual orientation. Here are some of the highlights, as reported by Diamond and Rosky:

  • In just 7 years, 30% of young adults with same-sex attraction changed to opposite-sex attraction;
  • Most, but not all, of this change involved bisexuals;
  • Of the homosexual young adults whose sexual orientation changed, 66% changed to heterosexuality;
  • All of these changes in sexual orientation occurred spontaneously;
  • Sexual orientation involved some degree of choice for many (10% of gay men, 30% of lesbians and 60% of bi-sexuals), according to one of the studies cited;
  • Homosexuality is fluid, not immutable;
  • The “born gay” claim is unscientific (i.e., not supported by the scientific research).

Perhaps the most often utilized and reliable of the several databases employed in such studies is the one called “Add Health.” Using this database, Udry and Chantala (Journal of Biosocial Science 37:481-497) found that 83% of 16-year-old, adolescent gay boys were neither gay nor bisexual one year later, at age 17. This same figure can be arrived at by doing the math on the data published by Savin-Williams and Joyner (Archives of Sexual Behavior 43:413-422), also from the Add Health database. Finally, Whitehead and Whitehead (click HERE) used the same Add Health data set to calculate that 98% of the 16-year-olds who were either homosexual or bisexual moved towards heterosexuality by age 17. In these studies, there was also a small percentage that moved from heterosexuality toward homosexuality. All of these changes in sexual orientation were spontaneous.

Whitehead and Whitehead (click HERE) also made the following pertinent observations from the published scientific literature:

  • Homosexuality is much more fluid than is heterosexuality, as 50% of homosexuals become heterosexual, but only 1.9% of heterosexuals become homosexual;
  • One study reported that 63% of lesbians and 50% of gay men, from age 18 to age 26, changed sexual orientation at least once;
  • Because of the higher levels of sexual orientation fluidity among homosexuals, at any given time there are more ex-gays than actual gays in the general population;
  • All of these reported changes in sexual orientation were spontaneous.

Mayer and McHugh (click HERE) recently published an extensive review of the scientific literature on sexual orientation. They supported the conclusions of others that:

  • There is strong scientific evidence that sexual orientation is fluid;
  • Women’s sexual orientation is consistently more fluid than men’s;
  • The sexual orientation of adolescents is more fluid that that of young adults;
  • Choice is a factor in the development of homosexuality.

So, in view of the sound, scientific evidence discussed above, we can conclude that the answer to this question is, “No, homosexuality is not immutable, but is, in fact, quite fluid.” Whitehead and Whitehead (click HERE) even went so far as to state that, “Rather than homosexuality being an unalterable condition, it is actually a good example of a changeable condition.” Thus, as with the born-gay hoax, real science has “outed” the immutability hoax.

Sexual Orientation Change Efforts (S.O.C.E.)

In view of the considerable amount of spontaneous fluidity of homosexuality, it should not be surprising that dissatisfied homosexual people can, in fact, change through S.O.C.E., the deceitful denials of gay activists notwithstanding. The success of efforts to help dissatisfied homosexual people change their sexual orientation toward heterosexuality through therapy and counseling is an integral part of the evidence against the “born gay” and the “immutability” claims. Such changes in sexual orientation have been amply documented for both secularly (click HERE) and religiously (click HERE) mediated efforts. Both approaches can be successful at a rate (~ 25%-30%) that is comparable to that for psychological disorders and for behavioral problems, such as alcoholism. While most of the individuals seeking S.O.C.E. have not experienced a 100% reversal in all aspects of sexual orientation, many, by their own testimony, have achieved substantial and meaningful changes in their sexual orientation that enable them to live celibate or exclusively heterosexual lifestyles that satisfy their personal goals. For the originally dissatisfied homosexual person, that is real, substantial and meaningful change. And there are thousands of former homosexuals who testify that they have changed (for examples, click HERE).

If homosexuality were determined by biological factors and immutable, then such transformations would not be possible. Thus, S.O.C.E. have “outed” both the “born gay” and the “immutability” hoaxes.

What Difference Does It Make?

The short answer is, it makes a huge difference, as discussed by Mayer and McHugh (click HERE) and Whitehead and Whitehead (click HERE). The homosexual movement has used the “born gay” hoax and its correlate, the “immutability” hoax, to not only deceive the public and gain popular support for their “gay agenda” (click HERE), but they have managed to deceive also medical societies, church leaders, teachers, politicians and judges at all levels. The result is that, based largely on these and other hoaxes perpetrated by the homosexual movement (click HERE, HERE, HERE, HERE and HERE), many churches, teachers and politicians have come to believe (erroneously) that homosexual behavior is not only normal, but also natural, healthy, desirable and moral. This development represents a serious spiritual and moral decay in America.

Furthermore, politicians and judges are hard at work codifying homosexuality into laws (e.g., so-called “gay marriage” and anti-discrimination laws). Laws criminalizing the practice of S.O.C.E. to help children and adolescents overcome unwanted homosexuality (click HERE and HERE) are particularly heinous, because they selectively deny professional help to people who are at the most sexually confusing and unstable phase in their lives. This gives gay activists an “open season”, as it were, to target these vulnerable minors for recruitment into a life of homosexuality without interference from contrary influences, such as professional counselors and therapists. And, in the process, children and adolescents are denied their right to self-determination and parental rights are trampled underfoot, all in the name of sexual liberty.

If not checked soon, the homosexual movement will seriously erode our First Amendment right to the “free practice of religion” in America. Already, sexual liberty is being put ahead of religious freedom, and laws have been passed forcing even churches, under penalty of law, to accommodate homosexuals and transgenders on their terms (click HERE and HERE). The “gay agenda” is a mammoth social experiment – based largely on lies, myths and hoaxes – that is reaping dire consequences for America and proving to be a mistake of biblical proportions.

Summary

Multiple, scientific studies of homosexuality in identical twin pairs have demonstrated conclusively that biological factors (including genetics) do not determine the development of homosexuality. “Born gay” is a hoax. Several large-scale, longitudinal, scientific studies, numerous personal testimonies and the success of both secularly and religiously mediated sexual orientation change efforts prove that homosexuality is, in fact, quite fluid, not immutable. “Immutability” is also a hoax. Unfortunately, the homosexual movement has been able to dupe our society and its religious leaders, politicians, medical societies and judges into believing their lies, myths and hoaxes. This charade is causing serious damage to the spiritual and moral condition of American society, and it is eroding the constitutional provision to practice religion freely, as sexual liberty is increasingly being placed above religious freedom in the formulation and application of anti-discrimination laws and ordinances. The homosexual movement is a social experiment that will have dire consequences, unless America repents and God intervenes.

(For more articles on homosexuality by Professor Aist, click HERE)

by

Cultures without Homosexuality: They Do Exist!

See the source image

Cultures without Homosexuality: They Do Exist!

James R. Aist

(Note: the numbers in parentheses refer to specific references listed at the end of the article)

Introduction

Homosexual activists often claim that homosexuality is universal among the cultures of the world. They do this to convince the heterosexual majority that homosexuality is normal, that it has a biological (genetic) basis and that it is immutable (unchangeable). To the extent that they can convince the heterosexual majority that this claim is true, they can garner support for the “gay agenda.” But is this claim really true? Do all of the cultures of the world really have homosexuality, and is homosexuality always a stable cultural characteristic? Let’s have a look at the evidence.

The Evidence

There are several kinds of cultural evidence indicating that homosexuality is not genetically determined, but is, instead, strongly influenced by post-natal events and factors. Much of this evidence was reviewed by Whitehead and Whitehead (1), and I will first mention some of the highlights of their review before moving on to other evidence. If causation of homosexuality were to be genetically determined, then it would appear in about the same percentage in all cultures, but this is clearly not the case. The prevalence of homosexuality has varied considerably in different cultures. For example, Ford and Beach (23) found that in the 79 cultures they surveyed, homosexuality was rare or absent in 29 and lesbianism was found in only 17. Homosexuality is also historically and exceptionally rare among Orthodox Jews. And among the genetically related tribes of the New Guinea Highlands, homosexuality was mandatory among one tribe, practiced by 2-3% of a second tribe and completely unheard of in a third tribe. A significant number of cultures appear not to have practiced homosexuality at all. Moreover, if causation of homosexuality were to be genetically determined, then its occurrence in any given culture would be stable over very long periods of time (e.g., 1,000 years or more), but in some cultures, homosexuality disappeared within several generations. Anthropologists attribute many such sudden changes in the occurrence of homosexuality to Christian influences, which represent a set of post-natal, non-biological, cultural factors.

Two original scientific studies merit particular mention in this regard. Broude and Greene (2), anthropologists from Harvard University, used the Standard Cross-Cultural Sample of 186 societies representing different and independent culture clusters within major areas of the world. This data base is considered to be the best representative sample of world cultures (3). They found that 12% of these cultures had “No concept of homosexuality.” Moreover, in 59% of these cultures, homosexuality was “Absent or rare.” A necessary conclusion from these results is that homosexuality does not exist in a great many of the cultures of the world. More recently, Hewlett and Hewlett (3), anthropologists from Washington State University, interviewed 35 members of an Aka forager band and 21 members of a Ngandu farmer village of the Central African Republic. The Aka had no concept of homosexuality, and it was absent from their culture. The Ngandu were familiar with the concept of homosexuality from visits by some village members to the capital city, but they had no word for it in their language. And homosexuality was absent in and around their village. In both of these cultures, sex was considered to be of paramount importance for the purpose of procreation and was highly valued primarily for that purpose alone. Furthermore, from a review of the relevant literature, these authors concluded that the Euro-American human sexuality literature, including some college textbooks, gives the false impression that homosexuality is a human universality. Whereas, in fact, the Euro-American patterns of homosexuality are quite unusual by cross-cultural standards; homosexuality is more common in this demographic than it is elsewhere in the world. By contrast, sexual practices of the Aka and Ngandu are not unusual by the same cross-cultural standards.

Conclusions

Homosexuality does not conform to any genetically prescribed model, but it does appear to have an overwhelmingly cultural component, ebbing and flowing with changes in cultural values, such as the introduction of Christianity, and with different cultural expectations (1). Several cultures do not even have a concept of homosexuality, and a great many have little or no homosexuality at all. Therefore, the claims by homosexual activists that homosexuality is universal among the cultures of the world and is immutable are patently and demonstrably false.

(For more articles on HOMOSEXUALITY, click HERE)

References Cited:

1. Whitehead, N. and B. Whitehead. 2012. Chapter 6. What do different cultures tell us about homosexuality? (click HERE)

2. Broude, G. and S. Greene. 1976. Cross-Cultural Codes on Twenty Sexual Attitudes and Practices. Ethnology 15:409-430.

3. Hewlett, B. and B. Hewlett. 2010. Sex and Searching For Children Among Aka Foragers and Ngandu Farmers of Central Africa. African Study Monographs 31:107-125. (click HERE)

by

What Twin Studies Tell Us about Homosexuality: Nature vs. Nurture

See the source image

What Twin Studies Tell Us about Homosexuality: Nature vs. Nurture

James R. Aist

(Note: Numbers in parentheses refer to specific, numbered references listed at the end of the article.)

Introduction

I presented a much broader treatment of possible causes of homosexuality elsewhere (click HERE). Most of the more recent research on possible biological origins of homosexuality has focused on the degree to which genes, along with other prenatal factors such as hormones and epi-genetics, may influence the development of homosexuality. In this regard, the most conclusive and telling results have come from studies of “identical” twins (who both have virtually the exact same complement of genes). Although it is commonly assumed that identical-twin studies reveal the influence of genes per se on a trait or behavior, the results of such studies have the unique advantage of reflecting, in fact, the combined influence of all possible, pre-natal, biological factors (e.g., genetics, epi-genetics, hormones, etc.) on the development of homosexuality in adults (1). This is because identical twins not only share the same complement of genes, but they also share the same pre-natal environment (their mother’s womb), where biological factors are postulated to operate.

Twin Studies: Overview

The design of research studies using identical twins has improved greatly since the mid-1990s, with the advent of large, twin registries which can afford much larger data bases and less biased sampling procedures. The former approach of recruiting identical twins via advertisements in gay and lesbian publications is now known to have a very strong “volunteer effect” that produced the appearance of relatively large genetic effects (1). Nevertheless, even with the use of large twin registries, the number of identical twin pairs found with homosexuality is often very small in individual studies, resulting in a standard deviation that is greater than the calculated genetic effect, meaning that the results are not statistically different from zero. In other words, the genetic influence or contribution in several of these studies may actually be zero, making definitive conclusions impossible. Whitehead and Whitehead (1) have presented and discussed, in some detail, these and other problems inherent in twin studies of homosexuality and have presented reasons to expect that the genetic influence on, or contribution to, homosexuality will eventually be agreed to be in the 10%-15% range (i.e., weak). One reason for this (anticipated) lower actual genetic influence is that epi-genetic effects operating through identical twins sharing one placenta probably represent about 15% of the total influence that has been attributed to genetics in published twin studies (2). Another reason has to do with the apparently predominant influence of post-natal environmental factors on the development of homosexuality (10). Schumm (9) found that children with homosexual parents are 12-15 times more likely than children of heterosexual parents to be homosexual as adults. This is the strongest environmental influence ever reported for the development of homosexuality, and it involves very close family members, the parent-child relationship. In a family environment, identical twins share a common bond and common experiences more so than do other siblings, including non-identical twins; siblings can’t be any “closer” than that. The results of a study by King and McDonald (8) illustrate how such a close, family relationship could inflate the calculated genetic influence on homosexuality in identical twin studies. They studied 46 twin pairs having homosexuality present in one or both of the twins in each pair and found that 54% of the twin pairs had discussed their sexual orientation with each other, 89% had “shared knowledge” of each other’s sexual orientation, and 30% of these twin pairs had actually had sex with each other. Because identical twins identify so closely with each other, and post-natal experiences  – especially close family relationships – strongly affect the development of homosexuality, it seems plausible, if not likely, that a homosexual member of a twin pair would influence the other member of that pair to embrace and explore homosexuality also, thus inflating the apparent genetic influence reported in identical twin studies. That is to say, a significant portion of what may appear, in identical twin studies, to be a genetic influence on the development of homosexuality may turn out to be, instead, a post-natal, environmental influence involving shared knowledge of sexual orientation and shared sexual experiences within identical twin pairs.

Twin Concordance Studies

The “pair-wise concordance” answers the simple question, “Where one twin of an identical pair is homosexual, what percentage of co-twins is also homosexual”. The mathematical formula for pair-wise concordance of identical twins is C/C+D, where C is the number of concordant (similar) twin pairs and D is the number of discordant (dissimilar) twin pairs found in the study. For example, if C=1 and D=9, then the pair-wise concordance would be 1/1+9=1/10 or 10%. This result would indicate that for every twin pair with both members being homosexual, there are 9 twin pairs with only one homosexual member.

Using data provided in several reports of large, twin registry studies in different countries, I performed a meta-analysis and calculated the range of pair-wise concordance to be 9.9% to 31.6%, with the average being 13.0% for males, 13.3% for females, and 13.2% when the raw data for males and females were combined. These pair-wise concordance values indicate that for every twin pair with both members being homosexual, there are 7 twin pairs with only one homosexual member. Now, compare this result to the range of theoretically possible outcomes where no twin pairs would both be homosexual (= 0%) and where all twin pairs would both be homosexual (= 100%) and you can see, intuitively, that a pair-wise concordance of only 13.2% would indicate a real, but relatively minor, contribution of genetics to homosexuality. This minor role is similar to the estimated level of genetic contribution to virtually any kind of human behavior (3) and is known to be non-determinative and, in many cases, treatable by therapy and/or counseling. For instance, the best example to date of a genetically related behavior (mono-amine oxidase deficiency leading to aggressive behavior) has shown itself remarkably responsive to counseling (3). Therefore, on the basis of pair-wise concordance in identical twins, it seems appropriate to conclude that there is, at the most, only a minor genetic contribution to the development of homosexuality, and that this relatively minor influence can be overcome (i.e., nullified) through behavioral therapy (1), which we know to be a fact (4, 5).

The other measure of concordance in twin studies is “proband-wise” concordance. This estimate of concordance is necessary in order to use both identical and fraternal twins in a study to disentangle the relative contributions to homosexuality of genetic and non-genetic (environmental) factors. The formula used is 2C/2C+D, which, compared to the formula for pair-wise concordance, gives much more weight to the individual twins (probands). The effect is to greatly increase, relative to pair-wise concordance values, the apparent genetic contribution to homosexuality in identical twin studies. To illustrate this point, if we use the example given above where the pair-wise concordance calculates to be 1/10 = 10.0%, the proband-wise concordance calculates to be 2/11 = 18.2%. Although it is less intuitive, proband-wise concordance is generally believed to give a better overall estimate of “genetic influence” than does pair-wise concordance.

Classical Twin Studies

While pair-wise concordance gives an intuitive indication of the genetic influence on homosexuality as expressed in identical twins, it does not provide information on what factors may provide the remaining, non-genetic influence. To answer this question, researchers are using other measures, broader-ranging questionnaires and more sophisticated statistical procedures to evaluate such things as heritability, additive genetic effects and postnatal environmental influences. In order to be able to put the results of classical twin studies into perspective, it is important to keep in mind that, by convention in the twin study literature in general, a genetic contribution of around 25% is considered weak, of around 50% is considered moderate and of 75% or more is considered strong (6).

In a meta-analysis, Whitehead (6), using the results from seven of the recent twin registry studies that were designed to reveal contributions of both genetic and non-genetic factors to homosexuality, found that the mean contribution of genetics to male homosexuality was around 22%, and to female homosexuality, around 33%. Because of the relatively large standard deviations in the data, these two values were not statistically different from each other.  Thus, the mean genetic contribution to male homosexuality in these studies is weak and to female homosexuality is weakly moderate. Such levels of genetic contribution indicate a real but weak-to-weakly moderate and indeterminate role of genetics in the development of homosexuality. For comparison, other traits that have around 50% (moderate and indeterminate) genetic contribution in twin studies include such things as divorce and alcoholism, while puberty has a 90% (strong and determinate) genetic contribution (1). Furthermore, the non-shared, post-natal environmental contribution to homosexuality is moderate to strong, around 64%-78%, has a relatively small standard deviation and is consistently around the same percentage (6), indicating that homosexuality is influenced primarily by post-natal environmental factors and experiences that are not directly related to prenatal, biological contributions of any kind or combination.

The recent study by Zietsch, et al. (7) can be used to illustrate representative research results obtained with large samples from twin registries. They used a very large sample (9,884) of twins from the Australian Twin Registry, one of the largest samples to date for twin studies of homosexuality. In this sample, there were 1,840 identical twin pairs (1,133 female and 707 male). Their calculated value of only 24% for the proband-wise concordance for homosexuality indicates a weak genetic influence. Moreover, their calculated figure of 31% for heritability of homosexuality also indicates a weak genetic component. This leaves around 68% of the variance represented by post-natal, “shared environment” and “residual” environmental influences combined.

Summary

In view of the fact that twin studies have shown that the combined influence of all possible, pre-natal, biological factors (e.g., genetics, epi-genetics, hormones, etc.) on the development of homosexuality in adults is only weak-to-moderate, it is important to understand that all of the biological theories combined can address only this weak-to- weakly moderate amount of influence, while ignoring the far more important post-natal influences (e.g., culture, parental divorce, and having a homosexual parent). Furthermore, twin studies clearly support the inference, based on results obtained through therapy and counseling (4, 5), that post-natal, environmental influences have a far greater role in the development of homosexuality than do pre-natal, biological influences. Thus, where the development of homosexuality is concerned, twin studies have demonstrated that nurture is far more important than nature.

(For more articles on HOMOSEXUALITY, click HERE)

References Cited:

1. Whitehead, N. and B. Whitehead. 2016. Chapter 10. Twin studies: The strongest evidence.(click HERE)

2. Whitehead, N. and B. Whitehead. 2016. Chapter 1. Can genes create sexual preferences? (click HERE)

3. Whitehead, N. and B. Whitehead. 2016. Summary. (click HERE)

4. Whitehead, N. and B. Whitehead. 2016. Chapter 12. Can sexual orientation change? (click HERE)

5. Aist, J. 2012. Homosexuality: Good News! (click HERE)

6. Whitehead, N.E. 2011. Neither Genes nor Choice: Same-sex Attraction is Mostly a Unique Reaction to Environmental Factors. Journal of Human Sexuality 3:81-114. (click HERE)

7. Zietsch, B., et al. 2012. Do Shared Etiological Factors Contribute to the Relationship between Sexual Orientation and Depression? Psychological Medicine 42:521-532.

8. King, M., and E. McDonald. 1992. Homosexuals who are Twins. British Journal of Psychiatry 160: 407-409.

9. Schumm, W. 2010. Children of Homosexuals More Apt to be homosexuals? A Reply to Morrison and to Cameron Based on an Examination of Multiple Sources of Data. Journal of Biosocial Science 42:721-742.

10. Aist, J. 2012. Are Homosexual People Really Born Gay? (click HERE)