What causes homosexuality

There is no single known cause. Sexual orientation (including homosexuality) appears to arise from a complex interplay of biological, developmental, and environmental factors: - Genetic influences: Family and twin studies show heritable components. Genome-wide studies find multiple genetic variants with small effects rather than a single “gay gene.” (e.g., Sanders et al. 2017; Ganna et al. 2019) - Prenatal biological factors: Hormonal exposures in the womb (e.g., fetal androgen levels), epigenetic markers, and maternal immune responses have been proposed as contributors. Evidence is suggestive but not determinative. (e.g., Bogaert 2018; Bogaert & Skorska 2011) - Neurodevelopmental differences: Some brain-structure and functional differences correlate with sexual orientation, but causality and specificity are unclear. (e.g., Swaab & Garcia-Falgueras 2009) - Psychosocial/environmental factors: Childhood experiences and social environment do not reliably predict adult sexual orientation; mainstream science rejects simple nurture-only explanations. - Multifactorial and probabilistic: Most researchers conclude sexual orientation emerges from multiple interacting causes and is not a choice. Authoritative summaries: American Psychological Association and National Academies of Sciences note that sexual orientation likely results from a complex mix of factors and cannot be attributed to a single cause.