What causes homosexuality

Explanation: Researchers propose that biological events before birth can influence later sexual orientation. Key hypotheses include: - Hormonal exposures: Variations in fetal androgen (male sex hormone) levels during critical periods of brain development may affect sexual attraction patterns. For example, lower prenatal androgens are often hypothesized to be associated with same-sex attraction in natal males, while higher prenatal androgens are considered in some explanations for same-sex attraction in natal females. - Epigenetic markers: Chemical modifications to DNA or its associated proteins that regulate gene expression (epigenetic changes) arising during fetal development may alter how genes involved in brain and sexual differentiation are expressed, potentially shaping sexual orientation without changing the genetic code itself. - Maternal immune responses: The maternal immune hypothesis suggests that maternal antibodies produced in response to male fetuses might, after multiple male pregnancies, influence brain development in later male fetuses in ways linked to increased likelihood of homosexual orientation (a proposed explanation primarily for older-brother effects in men). Evidence status: Empirical findings provide support for some associations consistent with these ideas (e.g., hormone measures, epigenetic patterns in small samples, and the older-brother effect), but results are mixed and effect sizes are often small. No single prenatal biological factor has been shown to deterministically cause homosexuality; current evidence is suggestive but not conclusive, indicating a likely interplay of multiple biological and environmental influences. References: - Bogaert, A. F. (2018). Commentary on prenatal influences on sexual orientation. [See reviews and empirical studies cited therein.] - Bogaert, A. F., & Skorska, M. N. (2011). The maternal immune hypothesis and older-brother effect literature. (References summarized for concision; consult the cited authors’ review articles and empirical papers for detailed evidence and methodology.)