Note: This is completely BOGUS. It has to do with the fact that some immature older brothers do haze their younger siblings, sometimes causing permanent emotional damage, it has nothing to do with biology. Families with half-brothers are fractured, and there are, evidently, reasons why the hazing is not as bad (the older brother is more likely to be insecure having lost his father, will be closer to his mother, and won't haze as much). This is a propaganda story that ignores those social factors.
http://newsvote.bbc.co.uk/mpapps/pagetools/print/news.bbc.co.uk/2/hi/health/5120004.stm
Womb environment 'makes men gay'A man's sexual orientation may be determined by conditions in the womb, according to a study.Previous research had revealed the more older brothers a boy has, the more likely he is to be gay, but the reason for this phenomenon was unknown.
But a Canadian study has shown that the effect is most likely down to biological rather than social factors.
The research is published in the journal of the Proceedings of the National Academy of Sciences.
Professor Anthony Bogaert from Brock University in Ontario, Canada, studied 944 heterosexual and homosexual men with either "biological" brothers, in this case those who share the same mother, or "non-biological" brothers, that is, adopted, step or half siblings.
These results support a prenatal origin to sexual orientation development in men
Professor Anthony BogaertHe found the link between the number of older brothers and homosexuality only existed when the siblings shared the same mother.
The amount of time the individual spent being raised with older brothers did not affect their sexual orientation.
'Maternal memory'
Writing in the journal, Professor Bogaert said: "If rearing or social factors associated with older male siblings underlies the fraternal birth-order effect [the link between the number of older brothers and male homosexuality], then the number of non-biological older brothers should predict men's sexual orientation, but they do not.
"These results support a prenatal origin to sexual orientation development in men."
He suggests the effect is probably the result of a "maternal memory" in the womb for male births.
A woman's body may see a male foetus as "foreign", he says, prompting an immune reaction which may grow progressively stronger with each male child.
The antibodies created may affect the developing male brain.
In an accompanying article, scientists from Michigan State University said: "These data strengthen the notion that the common denominator between biological brothers, the mother, provides a prenatal environment that fosters homosexuality in her younger sons."
"But the question of mechanism remains."
Andy Forrest, a spokesman for gay rights group Stonewall, said: "Increasingly, credible evidence appears to indicate that being gay is genetically determined rather than being a so-called lifestyle choice.
"It adds further weight to the argument that lesbian and gay people should be treated equally in society and not discriminated against for something that's just as inherent as skin colour."