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In northern Ghana, a region where male primogeniture predominates, rich households favoured sons over daughters. It is likely that first born sons would have been prefered as they would inherit the wealth and therefore have higher reproductive prospects.<ref>{{cite journal | title=Socioeconomic status determines sex-dependent survival of human offspring | author=van Bodegom, David; Rozing, Maarten P.; May, Linda; Meij, Hans J.; Thomése, Fleur; Zwaan, Bas J. and Westendorp, Rudi G. J. | journal=Evolution, Medicine, and Public Health | year=2013 | volume=2013 | issue=1 | pages=37-45 | doi=10.1093/emph/eot002}}</ref>
=== Possible relationship with male sexuality ===
The more older brothers a man has, the greater the probability is that he will have a homosexual orientation (the famous [[fraternal birth order effect]]). This is because, with each preceding pregnancy of a boy, a mother increases the release of antigens that feminize the brain of the next boy.<ref>Fraternal Birth Order and the Maternal Immune Hypothesis of Male Homosexuality Ray Blanchard 1 Centre for Addiction and Mental Health—Clarke Site, and Department of Psychiatry, Faculty of Medicine, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada http://classes.biology.ucsd.edu/bisp194-1.FA09/Blanchard_2001.pdf</ref> According to evolutionary explanations, mothers do this to prevent competition for resources between sons.<ref>Homosexuality, birth order, and evolution: towards a equilibrium reproductive economics of homosexuality; Edward M. Miller University of New Orleans http://scholarworks.uno.edu/cgi/viewcontent.cgi?article=1018&context=econ_wp&sei-redir=1&referer=http%3A%2F%2Fscholar.google.es%2Fscholar_url%3Fhl%3Des%26q%3Dhttp%3A%2F%2Fscholarworks.uno.edu%2Fcgi%2Fviewcontent.cgi%253Farticle%253D1018%2526context%253Decon_wp%26sa%3DX%26scisig%3DAAGBfm2ZvDPlWHkBIiS6bSvSR6R-pkFrwg%26oi%3Dscholarr%26ei%3Du1jQUZSOHsjJOa2sgegI%26ved%3D0CC0QgAMoATAA#search=%22http%3A%2F%2Fscholarworks.uno.edu%2Fcgi%2Fviewcontent.cgi%3Farticle%3D1018%26context%3Decon_wp%22</ref> Only having maternal elder brothers increases a male's chance of being homosexual; paternal elder brothers alone have no effect on a male's sexuality. According to Spanish chroniclers, among some Indigenous American peoples mothers used to make the youngest of various brothers dress and behave like a female. In many villages in northern Thailand, when a family had no daughters, the youngest son would sometimes become homosexual, dress and behave like a woman and fulfill some social obligations customarily ascribed to the youngest daughter, like performing ritual dances or remaining home unmarried caring for the parents. These gay youngest sons were called kathoey.<ref>Ladyboys and Good Sons: Contemporary Mediums and Gender Identity in northern Thailand http://escholarship.org/uc/item/23d2b5d8</ref> The custom of making the youngest of various sons homosexual also existed in many other places where mothers had high status, like Madagascar (sarombavy),<ref>Patterns of Sexual Behaviour http://books.google.es/books?id=WgsOAAAAQAAJ&pg=PA139&lpg=PA139&dq=%22Sarombavy%22+%22younger+sons%22&source=bl&ots=D5EnyvoVuD&sig=Zb62pd602FH5Lys2cRtEunGqpa0&hl=es&sa=X&ei=z1nQUeHQMceiO-jhgbgC&ved=0CC0Q6AEwAA#v=onepage&q=%22Sarombavy%22%20%22younger%20sons%22&f=false</ref> Tonga (fakafefine),<ref>Birth Order in the Fakafefine options KENNETH J. ZUCKER & RAY BLANCHARD http://www.tandfonline.com/doi/abs/10.1080/00926230390195489#.UdBaHOSIGZ8</ref> Samoa (fa'afāfine),<ref>Male Sexual Orientation in Independent Samoa: Evidence for Fraternal Birth Order and Maternal Fecundity Effects Doug P. VanderLaan, Paul L. Vasey http://link.springer.com/article/10.1007/s10508-009-9576-5</ref><ref>Birth order in transgendered males from Polynesia: a quantitative study of Samoan fa'afāfine. Poasa KH, Blanchard R, Zucker KJ. Source Department of Psychology and Professional Counseling, Northwest Christian College, Eugene, Oregon. http://www.ncbi.nlm.nih.gov/pubmed/14660290</ref> or Burma (accault). Although no such custom existed anywhere in the more patriarchal cultures of the West, a positive correlation between number of maternal elder brothers and a male's chance of being homosexual exists among many human groups for whom a historical negative correlation between number of elder brothers and reproductive success is attested, such as [[North Americans]],<ref>Birth Order and the Maternal Immune Hypothesis of Male Homosexuality Ray Blanchard http://classes.biology.ucsd.edu/bisp194-1.FA09/Blanchard_2001.pdf</ref> English,<ref>Lancet. 1962 Jan 13;1(7220):69-71. Birth order and maternal age of homosexuals. SLATER E. http://www.ncbi.nlm.nih.gov/pubmed/13913808</ref><ref>Birth order and ratio of brothers to sisters in transsexuals. Green R. http://www.ncbi.nlm.nih.gov/pubmed/11037086</ref> Welsh,<ref>Parental age and birth order in homosexual patients: a replication of Slater's study. Hare EH, Moran PA. http://www.ncbi.nlm.nih.gov/pubmed/427334</ref> Italians,<ref>Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity Andrea Camperio-Ciani http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691850/pdf/15539346.pdf</ref> Spanish,<ref>Birth Order and Ratio of Brothers to Sisters in Spanish Transsexuals http://portal.uned.es/pls/portal/docs/PAGE/UNED_MAIN/LAUNIVERSIDAD/UBICACIONES/02/DOCENTE/ANTONIO_GUILLAMON_FERNANDEZ/GOMEZ-GIL%20ET%20AL%202010A.PDF</ref> [[Dutch language|Dutch]],<ref>Birth order and sibling sex ratio in two samples of Dutch gender-dysphoric homosexual males Ray Blanchard Ph.D., Kenneth J. Zucker Ph.D., Petty T. Cohen-Kettenis Ph.D., Louis J. G. Gooren M.D., Ph.D., J. Michael Bailey Ph.D. http://link.springer.com/article/10.1007/BF02437544</ref> Japanese<ref>Sexual orientation in men and avuncularity in Japan: implications for the kin selection hypothesis. Vasey PL, VanderLaan DP. http://www.ncbi.nlm.nih.gov/pubmed/21656333</ref> and Han Chinese.<ref>Tsoi, W. F., Kok, L. P., & Long, F. Y. (1977). Male transsexualism in Singapore: A description of 56 cases</ref> Among all these peoples, the more older brothers a man has, the greater the probability is that he will have a homosexual orientation, probably because elder brothers historically reduced the reproductive success of younger brothers.<ref>Interfamily Conflict, Reproductive Success, and the Evolution of Male Homosexuality. By Apostolou, Menelaos Review of General Psychology, Aug 26, 2013 http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=2013-30303-001</ref> However, the contrary pathiarchal custom of a father depriving his elder sons of his patrimony, thereby decreasing their reproductive opportunities, and making his youngest son heir with the intention of delaying his age of retirement also existed among some peoples. It was typical of some [[Tibeto-Burman]] groups like the [[Lushei]]. In Europe it was most common among the [[Sami people|Sami]] and most German-speaking groups.
== Cultural patterns of child-preference ==
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