The Science Behind Who We Are
Understanding the Biological Roots of Sexual Orientation and Gender Identity
In my writing on this blog thus far, I focus on topics related to differentiation in relationships - helping people balance connection with others while maintaining their own sense of self. But for this post, I want to talk about something different: the biological origins of sexual orientation and gender identity.
I’m sharing this because, in the current climate, LGBTQIA+ individuals, particularly trans people, are facing unprecedented challenges due to harmful sociopolitical rhetoric, fear-mongering, and outright falsehoods. These attacks often ignore scientific truth, perpetuating stigma and creating barriers to rights, health, and well-being. It is vital to counter these misconceptions with factual information.
This isn’t about politics; it’s about humanity. Understanding that sexual orientation and gender identity are natural and biologically rooted helps to affirm the dignity and worth of LGBTQIA+ individuals. It also provides a path for allies, families, and friends to better support their loved ones with compassion and clarity.
Biological Foundations: Genetics, Hormones, and Development
Sexual orientation and gender identity are not choices or the result of social influences - they are biologically determined before birth. Extensive research highlights the following mechanisms that shape these traits:
Prenatal Hormones: Research on prenatal hormone exposure provides compelling evidence of the biological foundations of sexual orientation. For instance, studies have shown that differences in prenatal androgen levels - hormones like testosterone - can influence later sexual orientation. Individuals exposed to higher levels of androgens in utero are more likely to exhibit same-sex attractions or gender nonconforming behavior, regardless of their assigned sex at birth. This evidence is supported by studies of congenital adrenal hyperplasia (CAH), a condition that increases androgen exposure during fetal development. People with CAH assigned female at birth have a higher likelihood of same-sex attractions compared to the general population. Additionally, differences in androgen exposure affect the development of the hypothalamus, a brain region associated with gender and sexual behavior.
Neuroanatomy: Brain imaging studies consistently show structural differences in cisgender and transgender individuals that align with their experienced gender. For example, the bed nucleus of the stria terminalis (BSTc), a brain region involved in gender identity, is similar in size and activity between transgender women and cisgender women, but not cisgender men, regardless of hormone therapy.
Epigenetics: Environmental factors during pregnancy influence how genes are expressed without altering the underlying DNA. These epigenetic changes can explain how identical twins, with the same genetic code, can sometimes differ in their sexual orientation or gender identity.
Cross-Species Evidence: Same-sex behavior is observed in over 1,500 animal species, from dolphins to penguins to primates. For example, certain rams show a consistent preference for other male rams, a behavior linked to brain differences and hormonal influences. These findings underscore that same-sex attraction is a natural part of biological diversity.
These biological processes mirror how other traits - such as eye color or left-handedness - are naturally determined. Just as left-handedness was once misunderstood and stigmatized, we now understand that diversity in gender and orientation is a natural part of human variation.
Markers of Gender Differentiation Before Birth
Scientific studies have uncovered specific markers of prenatal differentiation that provide tangible evidence of how sexual orientation and gender identity develop:
Finger Length Ratios (2D:4D): A well-documented marker of prenatal androgen exposure, the ratio of the second to fourth fingers is often shorter in individuals exposed to higher levels of testosterone in utero. Research has found correlations between this marker and both sexual orientation and gender identity, providing a measurable link to biological processes.
Pheromone Responses: Studies have shown that homosexual men and women respond differently to pheromones compared to heterosexual individuals. For example, gay men’s hypothalamus reacts to male pheromones in a way that mirrors heterosexual women, indicating a neural basis for sexual orientation.
Behavioral Studies in Early Childhood: Studies have shown that gender-typical play preferences, such as toy selection, often emerge as early as age two and correlate with prenatal hormonal influences rather than parental encouragement. This further supports the biological origins of gender identity.
The Health Impacts of Stigma and the Importance of Affirmation
Despite overwhelming scientific evidence, societal stigma often marginalizes LGBTQIA+ individuals, creating unnecessary barriers to health and well-being. Studies show that rejection, discrimination, and lack of affirming spaces contribute to disproportionately high rates of anxiety, depression, and suicidal ideation among LGBTQIA+ populations.
But there is a clear solution: affirmation. Research consistently demonstrates that when LGBTQIA+ individuals are supported by their families, communities, and healthcare providers, their mental health outcomes improve significantly. For example, a 2016 study found that transgender individuals who receive gender-affirming medical care experience reduced rates of depression and anxiety, often comparable to the general population.
Affirmation is not just about acceptance - it’s about creating environments where individuals feel seen, valued, and celebrated. When we recognize that sexual orientation and gender identity are natural and biologically determined, we can build a world where everyone has the opportunity to thrive.
A Message of Hope
The science is clear: sexual orientation and gender identity are deeply rooted in biology, not choices or social constructs. They are as integral to who we are as our fingerprints or the way our hearts beat. This understanding offers hope for a future where diversity is celebrated, and harmful myths are dispelled.
To LGBTQIA+ individuals: You are perfect exactly as you are. Your identity is valid, natural, and worthy of celebration. To allies, families, and friends: Your understanding and support can dramatically change lives. Together, we can create a world where everyone is free to be themselves and to thrive.
References
LeVay, S. (2011). From mice to men: Biological factors in the development of sexuality. Frontiers in Neuroendocrinology, 32(2), 110–113.
Rahman, Q., & Wilson, G. D. (2003). Sexual orientation and the 2nd to 4th finger length ratio: Evidence for organizing effects of sex hormones. Psychoneuroendocrinology, 28(3), 288–303.
Swaab, D. F., & Garcia-Falgueras, A. (2009). Sexual differentiation of the human brain in relation to gender identity and sexual orientation. Functional Neurology, 24(1), 17–28.