Harvard and MIT Scientists: Genetics and same-sex sexual behavior

Scientists from the UK, USA, Netherlands, Australia, Sweden & Denmark have studied the relationship between genetics and same-sex sexual behavior.

Their research was published in the August 2019 edition of Science. Its title is "Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior".

The report sets out the study’s purposes saying, ‘While the relationship between genetics and human same-sex sexual behavior has been studied in the past, this previous research has often lacked a high degree of precision.

For the first time, new largescale datasets afford sufficient statistical power to identify genetic variants associated with same-sex sexual behavior (ever versus never had a same-sex partner), estimate the proportion of variation in the trait accounted for by all variants in aggregate, estimate the genetic correlation of same-sex sexual behavior with other traits, and probe the biology and complexity of the trait.”

For this study, the researchers, representing six institutions, wanted to use rigorous genetic and statistical methods to study existing data that have been made available for scientific research worldwide. Beginning in 2017, they performed genome-wide association studies (GWAS) using genetic data from nearly 500,000 participants in UK, USA and Sweden. The researchers received permission to analyze the datasets. Participants were also asked questions about engaging in same-sex behaviour.

 

Summary of the study findings

1) There is no gay gene

Ben Neale, an associate professor in the Analytic and Translational Genetics Unit at Massachusetts General Hospital and one of the lead researchers on the international team, said, “There is no single gay gene, and a genetic test for if you’re going to have a same-sex relationship is not going to work. It’s effectively impossible to predict an individual’s sexual behavior from their genome.”

While the general public may find this surprising, the scientists doing the study and the scientific community that reviewed the study do not find this surprising.

 

2) Genes influence but do not cause same-sex behaviour. Environmental factors also influence same-sex behaviour

The report states that genetics does play a role in same-sex behaviour. The influence comes not from one gene but many, each with a tiny effect. Social or environmental factors also influence same-sex behaviour.

A person's developmental environment - the influence of diet, family, friends, neighbourhood, religion, and a host of other life conditions - was twice as influential as genetics on the probability of engaging in same-sex behaviour.

Genetic factors account for, at most, 8 - 25% of same-sex behaviour. Ben Neale said: "Genetics is less than half of this story for sexual behaviour, but it's still a very important contributing factor.”

 

3) 5 specific genetic variants were found to be particularly associated with same-sex behaviour

The report says, “These 5 markers do not define someone’s sexual behaviour. Behavioral traits, like sexual behavior and orientation, are only partially genetic in nature. They are shaped by hundreds or thousands of genetic variants, each with a very small effect, yet they are also shaped in large part by a person’s environment and life experiences."

The report says, “Each marker has a very small effect individually — that is, each contributed very little to a person’s sexual behavior. This is not unusual for complex human outcomes. Common genetic variants (typically defined as variants that appear in at least 1% of the population) often contribute only a tiny amount to the variation in the overall outcome.”

The report says, “It is important to remember that these genetic variants alone do not define someone’s sexual behavior. Behavioral traits, like sexual behavior and orientation, are only partially genetic in nature. They are shaped by hundreds or thousands of genetic variants, each with a very small effect, yet they are also shaped in large part by a person’s environment and life experiences. The study can therefore say with confidence that there is neither a single genetic determinant of nor single gene for same-sex sexual behavior or sexual orientation. To the extent that sexuality is influenced by genetics, it is more likely that hundreds or thousands of genetic variants are involved. These variants, together with the environment and experiences, shape outcomes like same-sex sexual behavior.”

The report also says, “These results do not make any conclusive statements about the degree to which “nature” and “nurture” influence sexual orientation or behavior, but indicate that both are likely to play a role.”

 

4) Using genetic data, the study found evidence that sexual behavior is a highly complex trait and that there is not a single dimension of sexuality

The study found that the genetic influences that contribute to the chance of having exclusively same-sex partners are largely distinct [different] from the genetic influences that contribute to having mostly opposite-sex partners.

The report says, The genetics suggest that it is an oversimplification to assume that the more someone is attracted to the same sex, the less they are attracted to the opposite sex. The study findings call into question the validity of single continuum measures like the Kinsey scale.

 

5) Caution in Making Broad Conclusions

The report itself and other commentaries on the study caution readers in making broad conclusions from the report. Considering the large sample size and power of Ganna et al.’s dataset, the small number and weak effect sizes of the GWAS hits identified seem to reflect the limitations of such studies. A caveat to GWAS exists in its acronym: association studies identify correlations, and correlation does not necessarily equal causation. This study reinforces the finding that same-sex sexuality is complicated. Simplistic statements such as people are born gay or people choose to be gay distort what people actually experience. Both genetics and non-genetic factors play important roles. It is time to stop asking is this caused by nature or nurture. Science has shown this is not a valid question because both likely play a role.

 

How does this report help?

We are so influenced by the myth that our genes and our past experiences control who we are that we often have difficulty thinking that we can make choices. We can struggle with faith in God when experiencing same-sex attractions. Our faulty thinking says, “God made me a certain way, I have no choice”. The Bible says differently, saying that we are truly free to choose God's way or our way. This is an awesome thing. It is one facet of being made "in the image of God". This study says that a person's developmental environment--the influence of diet, family, friends, neighbourhood, religion, and a host of other life conditions--was twice as influential as genetics on the probability of engaging in same-sex behaviour. These factors can be adjusted by our choices.

The Bible and science tell us that we can make choices. Twin studies show that identical twin brothers, growing up with the same parents, in the same time and place, at the same point in history, can experience different outcomes. This study reports that sexual behaviour and orientation are only partially genetic in nature. And the decisions we make have an impact on such outcomes. We need to stress here, as we do so often, that no one chooses to experience same-sex attractions. But our decisions have consequences that go far beyond what we can anticipate. We can choose how we will respond to our life situation. There is an element of choice in who we become.

This is indeed good news, because we can make new choices, and we can have new experiences of growth and healing that offer the possibility of very significant change for people experiencing same-sex attractions or involved in same-sex behaviour. Scriptures describe Christian life as being born again, becoming a new creation and changing from being dead to alive. God invites people, including those with same-sex attractions, to have an intimate relationship with Christ and develop a capacity for living with integrity in Christ. Don’t let misrepresentations about genetics persuade you that God’s invitation doesn’t apply to you or that your experience of same-sex attractions prevents you from experiencing it.

 

 

References

Study: Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior. Science. DOI: 10.1126/science.eaat7693.

Study Website: https://geneticsexbehavior.info/

Reference: https://www.broadinstitute.org/news/perspectives-complex-genetics-same-sex-sexual-behavior