Question explored with the scientific record
what is the cause of homosexuality
The evidence retrieved does not contain a single study that investigates the cause of human sexual orientation.
The fifteen records you provided cover plant sex chromosomes [1], disorders of sexual development [3, 4], fruit fly starvation genetics [6], bird clutch size [7], HIV resistance [10, 11], STI epidemiology [2, 12], cervical cancer [8], erectile dysfunction [9], OCD and sexuality [15], and one brain-volume study comparing homosexual and heterosexual women [14]. That 2007 brain study found less grey matter in the perirhinal cortex of homosexual women [14], but it is a correlation, not a cause. It does not tell you whether the brain difference preceded orientation or resulted from it.
The hypothesis you stated—complex interaction of genetic, prenatal hormonal, neurodevelopmental, and environmental factors—is the consensus view in the scientific literature. But the evidence set you gave me does not test it. None of these studies was designed to answer the question of what causes homosexuality. The gap is not subtle. It is total.
My call: the evidence retrieved does not address the cause of sexual orientation. Confidence: not applicable—the question cannot be answered from these records.
Sources examined 15
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Mercurialis: Old problems, new perspectives
This study investigates the genetic control and geographic distribution of sexual variants in dioecious and monoecious plants of the genus Mercurialis, revealing a complex polyploidy system and its implications for adaptation to various climates.
DOI: 10.1080/11263509609439503 -
Epidemiological and Genetic Correlates of Incident Chlamydia trachomatis Infection in North American Adolescents
This study investigates the epidemiological and genetic factors associated with Chlamydia trachomatis infection in a cohort of high-risk North American adolescents, revealing significant predictors such as age, number of sexual partners, and specific HLA gene variants.
DOI: 10.1086/425077 -
Diagnostic Application of Targeted Next-Generation Sequencing of 80 Genes Associated with Disorders of Sexual Development
This study evaluates the diagnostic yield of targeted next-generation sequencing of 80 genes associated with disorders of sexual development (DSD) in a cohort of 32 patients, revealing a significant increase in diagnostic rates compared to traditional single gene tests.
DOI: 10.1038/srep44536 -
The clinical diversity and molecular etiology in 46, XY disorders of sex development patients without uterus
This study investigates the clinical diversity and molecular etiology of 46, XY disorders of sexual development (DSDs) without a uterus, identifying novel genetic variants through whole exome sequencing and reverse phenotyping.
DOI: 10.1186/s13023-025-03719-y -
The handicap principle—A comment
A critical, theory-based re-evaluation of Zahavi's handicap principle by Maynard Smith, using a three-locus diploid genetic model (handicap, choosiness, and fitness) and monogamy variants, concluding that the proposed mechanism is not universally convincing and that the original…
DOI: 10.1016/0022-5193(78)90351-x -
Pervasive sex-dependent effects in the genetic architecture of starvation resistance in Drosophila melanogaster
A population cage sorting and sequencing (PCSS)–based, polygenic screen in natural Drosophila melanogaster reveals widespread sex-dependent and sexually antagonistic genetic influences on starvation resistance, with functional validation of key genes (including Lnk V58M via CRIS…
DOI: 10.1126/sciadv.adt3560 -
Genome-wide association mapping in a wild avian population identifies a link between genetic and phenotypic variation in a life-history trait
This study employs genome-wide association mapping in a wild population of collared flycatchers to identify genetic variants associated with clutch size, revealing a significant SNP on chromosome 18 that explains 3.9% of the phenotypic variance and suggesting the presence of sex…
DOI: 10.1098/rspb.2015.0156 -
Inherited alterations of TGF beta signaling components in Appalachian cervical cancers
This study investigates the genetic variants of transforming growth factor beta (TGFB) signaling in Appalachian women with cervical cancer, revealing significant associations between specific polymorphic alleles and cancer risk, influenced by lifestyle factors such as smoking an…
DOI: 10.1007/s10552-019-01221-y -
T01-P-09 MTHFR gene and erectile dysfunction
This article reports two studies: an online cross-cultural survey comparing sexual attitudes and behaviours in Australian and Polish adults, and a case report suggesting a possible link between a thermolabile MTHFR variant and erectile dysfunction, including response to folic ac…
DOI: 10.1016/s1158-1360(08)72678-1 -
Functionally-informed fine-mapping identifies genetic variants linking increased CHD1L expression and HIV restriction in monocytes
This study employs a functionally-informed fine-mapping approach to identify genetic variants associated with increased CHD1L expression that may restrict HIV replication in monocytes among individuals of African ancestry.
DOI: 10.1038/s41598-024-84817-y -
The pilot study of the features of HIV-1 resistant variants spread using molecular clusters
This pilot study in the Oryol region of Russia validates the use of HIV-1 molecular clustering to understand the spread of drug resistance, revealing predominant sub-subtype A6 with rising CRF63_02A6, substantial drug resistance among ART-experienced individuals, limited cluster…
DOI: 10.36233/0372-9311-565 -
Immunogenetic Correlates of Neisseria gonorrhoeae Infection in Adolescents
This study investigates the immunogenetic correlates of Neisseria gonorrhoeae infection in adolescents, revealing significant associations between specific genetic variants and cytokine responses related to gonorrhea.
DOI: 10.1097/olq.0b013e31816b6593 -
Deep comparative genomics among Chlamydia trachomatis lymphogranuloma venereum isolates highlights genes potentially involved in pathoadaptation
This study conducts a deep comparative genomic analysis of Chlamydia trachomatis lymphogranuloma venereum isolates, revealing significant genetic variability and identifying genes potentially involved in pathoadaptation and virulence.
DOI: 10.1016/j.meegid.2015.02.026 -
Homosexual Women Have Less Grey Matter in Perirhinal Cortex than Heterosexual Women
This study investigates the structural brain differences between homosexual and heterosexual women, revealing that homosexual women have less grey matter in the perirhinal cortex compared to heterosexual women.
DOI: 10.1371/journal.pone.0000762 -
Sexuality and Related Disorders in OCD and Their Symptoms
This narrative review synthesizes two decades of research on sexuality in OCD, detailing high prevalence of sexual dysfunction and sexual obsessions in OCD, their neurobiological and cognitive correlates, effects on treatment and prognosis, and the need for targeted, individuali…
DOI: 10.3390/jcm14196819