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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Birth order | 3/3 | https://en.wikipedia.org/wiki/Birth_order | reference | science, encyclopedia | 2026-05-05T15:31:34.215227+00:00 | kb-cron |
== Sexual orientation == The fraternal birth order effect is the name given to the theory that the more older brothers a man has, the greater the probability is that he will have a homosexual orientation. The fraternal birth order effect is said to be the strongest known predictor of sexual orientation, with each older brother increasing a man's odds of being gay by approximately 33%. (One of the largest studies to date, however, suggests a smaller effect, of 15% higher odds.) Even so, the fraternal birth order effect only accounts for a maximum of one-seventh of the prevalence of homosexuality in men. There seems to be no effect on sexual orientation in women, and no effect of the number of older sisters. In Homosexuality, Birth Order, and Evolution: Toward an Equilibrium Reproductive Economics of Homosexuality, Edward M. Miller suggests that the birth order effect on homosexuality may be a by-product of an evolved mechanism that shifts personality away from heterosexuality in laterborn sons. According to Miller, this would have the consequence of reducing the probability of these sons engaging in unproductive competition with each other. Evolution may have favored biological mechanisms prompting human parents to exert affirmative pressure toward heterosexual behavior in earlier-born children: As more children in a family survive infancy and early childhood, the continued existence of the parents' gene line becomes more assured (cf. the pressure on newlywed European aristocrats, especially young brides, to produce "an heir and a spare"), and the benefits of encouraging heterosexuality weigh less strongly against the risk of psychological damage that a strongly heteronormative environment poses to a child predisposed toward homosexuality. More recently, this birth order effect on sexuality in males has been attributed to a very specific biological occurrence. As the mother gives birth to more sons, she is thought to develop an immunity to certain male-specific antigens. This immunity then leads to an effect in the brain that has to do with sexual preference. Yet this biological effect is seen only in right-handed males. If not right-handed, the number of older brothers has been found to have no prediction on the sexuality of a younger brother. This has led researchers to consider if the genes for sexuality and handedness are somehow related. Not all studies, including some with large, nationally representative samples, have been able to replicate the fraternal birth order effect. Some did not find any statistically significant difference in the sibling composition of gay and straight men; this includes the National Longitudinal Study of Adolescent to Adult Health, the largest U.S. study with relevant data on the subject. Furthermore, at least one study, on the familial correlates of joining a same-sex union or marriage in a sample of two million people in Denmark, found that the only sibling correlate of joining a same-sex union among men was having older sisters, not older brothers.
== Research == Adler's theory of birth order has been used for further research. It has been discovered at a historically Black university, a significant difference was found between the drinking habits of firstborn versus last-born children, who were at a higher risk for alcohol-related behaviors. A study entitled "The Relationship of Birth Order and Gender with Academic Standing and Substance Use Among Youth in Latin America" used many test models, including Adler’s Birth Theory. The researchers determined that being a firstborn, regardless of gender, created "a protective factor against substance use" and an improved academic standing compared to subsequent children. These tests in Latin America revealed a real difference across multiple categories of life based on sibling order.
== Traditional naming of children according to their birth order == In some of the world's cultures, birth order is so important that each child within the family is named according to the order in which the child was born. For example, in the Aboriginal Australian Barngarla language, there are nine male birth order names and nine female birth order names, as follows:
Male: Biri (1st), Warri (2nd), Gooni (3rd), Mooni (4th), Mari (5th), Yari (6th), Mili (7th), Wanggooyoo (8th) and Ngalai (9th). Female: Gardanya (1st), Wayooroo (2nd), Goonda (3rd), Moonaga (4th), Maroogoo (5th), Yaranda (6th), Milaga (7th), Wanggoordoo (8th) and Ngalaga (9th). To determine the suitable name for the newborn child, one first finds out the number of the newborn within the family, and only then chooses the male/female name, according to the gender of the newborn. So, for example, if a baby girl is born after three boys, her name would be Moonaga (fourth-born, female) as she is the fourth child within the family. In some modern-day Western cultures, it is common for parents to give their children the same name as them. This tradition dates back to the 17th century and is most prevalent in fathers and sons, where the son will receive the same first name, middle name, and surname with either a "Jr.", "II", "III" or "IV", etc. attached after the family surname. This practice started as a symbol of status for "upper-class" citizens, but is now more commonly used as a family tradition, not necessarily implying that they are of a "higher status" than their peer(s), sibling(s) or other family members. The tradition of a father naming his son after himself or a male relative from an earlier generation (grandfather, great-grandfather) is referred to as "patronymic", while the tradition of a mother naming her daughter after herself or a female relative from an earlier generation (grandmother, great-grandmother) is referred to as "matronymic".
== See also ==
== References ==
== External links == "Development of the Firstborn Personality Scale". Self-report scale developed empirically to predict first born status. Includes open-access dataset. Birth order and intelligence The Independent article USA Today article on CEOs Investigating the effects birth order has on personality, self-esteem, satisfaction with life and age