Homosexuality in men corrolated to birth order

WASHINGTON - Men who have several older brothers have an increased chance of being gay — whether they were raised together or not — a finding researchers say adds weight to the idea that sexual orientation is based in biology.

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The increase was seen in men with older brothers from the same mother, but not those who had stepbrothers or adopted brothers who were older.

"It's likely to be a prenatal effect," said Anthony F. Bogaert of Brock University in St. Catharines, Canada, who did the research. "This and other studies suggest that there is probably a biological basis" for homosexuality.