Sexual orientation, handedness, sex ratio and fetomaternal tolerance-rejection

Abstract

Fraternal birth order (FBO) appears as a prenatal cause of 15% of homosexual males (gays) through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1) androgenic factors of nonright-handedness neutralize anti-male factors; (2) non-right-handedness and homosexuality are lethal or produce mental impairment; (3) non-right-handed male embryos are insensitive to anti-male factors; (4) mothers of non-right-handed fetuses do not produce antimale factors. Studies of the sex ratio (SR) of older and younger siblings show: (1) a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2) lesbians are born among siblings with high SR; (3) siblings of righthanded gays show a higher SR than non-right-handed gays that present a low SR. Based on our discovery of maternal tolerancerejection processes, associated with genetic systems (ABO, Rh), where zygotes or embryos different from their mother induce better pregnancy and maternal tolerance than do those that share antigens with their mothers, I propose a new explanation for sexual relationships, sexual orientation, handedness and sibling SR. Lesbian embryos could induce tolerance from mothers with anti-female factors. Non-right-handedness could induce maternal tolerance, or change the maternal compatibility of "gay" embryos. Alternatively, gay embryos could be poor inducers of maternal tolerance towards male traits.Key terms: homosexuality, handedness, sex ratio, birth order, fetomoternal tolerance, genetic distortions biological brothers, reared together or apart from the index homosexual case, are responsible for FBO effect. The probability of being homosexual increases as the number of older brothers increases. Handedness interacts with homosexuality and the SR of siblings; homosexuality, due to FBO, affects non-right-handed men less (Blanchard, 2001(Blanchard, , 2004Blanchard and Bogaert, 1996;Cantor et al., 2002;Bogaert, 2003Bogaert, , 2005Bogaert, , 2006, a relationship explained hypothetically by four prenatal mechanisms Lippa, 2006, 2007;Blanchard, 2008): (1) androgenic factors associated with non-right-handedness could cancel maternal anti-male factors leading to homosexuality; (2) homosexuality and non-right-handedness together may lead to death, neuro-psychic impairment or any condition that confers a low probability of being ascertained; (3) non-right handed fetuses my be insensitive to maternal anti-male factors; (4) mothers of non-right handed fetuses do not produce anti-male factors. The FBO was found also in transsexuals whose sexual identity, rather than their sexual orientation, is altered (Green, 2000). These hypotheses are in contradiction with the fact that non-righthandedness is more frequent in homosexual men (gays) and women (lesbians) than in heterosexuals (Lalumiére et al., 2000; this study). A hypothetical reconciliation of these contradictory facts was presented by Blanchard (2008). The authors (of the FBO hypoth...

Evidence for distinct biodevelopmental influences on male sexual orientation

“…Although the aforementioned biomarkers of male sexual orientation have been studied rather extensively in isolation, little research has investigated the relationships among them. A few studies considered both birth order and handedness, finding that the fraternal birth order effect is only related to sexual orientation in righthanded gay men (i.e., not mixed or left-handed men) (45,51,53,54). These results are consistent with the possibility that different male sexual orientation biomarkers delineate distinct biodevelopmental pathways and the existence of subgroups of gay men.…”

Human Sociogenetics

“…This difference is maintained in samples from blood donors, along with the SES, in the English study (Beardmore and Karimi-Booshehri, 1984) and among samples of medical students (high SES), a random sample of children participating in a longitudinal study (low SES), blood donors and blood receptors in Chile (Valenzuela and Harb, 1977;Valenzuela et al, 1980;Valenzuela, 1988). Alternatively a cytogenetic process named consociated chromosome segregation (the Y chromosome may be associated preferentially to one chromosome 9, where the ABO system is coded, see Valenzuela et al, 1980) and a strong association of ABO, Rh and other genetic systems with the sex ratio at birth , Valenzuela, 2010 can partially explain this association in Chile, but not in England. Thus the interaction of the SGC with gender is additional evidence for the true relationship between genetic factors and SES.…”

The Ontogenetic Origin of Human Beings in the Scientific-Ethics Perspective and its Implications on Abortion

“…It is interesting to remark how the huge advances in Physics, Biology (evolution, genetics and genomics), Chemistry, Cybernetics, and other scientific disciplines are not full accepted and incorporated into philosophies, ethics and theologies. Now we know there are genes involved in sexual fidelity, polygamy and monogamy and others behavioral traits with ethical or moral transcendence in animal and humans [44][45][46]; the prenatal conditioning of sexual phenotypes such as trans-sexuality and homosexuality has been also established by studies on the influence of sibling birth order in sexual orientation and sexual identity [47][48][49] and in studies of human mutants for "sexual" hormones [50][51][52][53]; we also found a great sex dimorphism, at birth and the following years, in the serotonergic nuclei of the brain stem involved in sexual dimorphic behaviors [54,55]. However, moral-theologians, ethicists, bioethicists and lawyers do not seem to have included these facts into their analyses.…”