Transsexuals may be right in saying they feel different, because they have brains more like a woman's than a man's, according to scientists in The Netherlands.
Dr Dick Swaab, from the Netherlands Institute for Brain Research, Amsterdam, found a part of the brain important for sexual behaviour is larger in men than in women. The region was of female size, or smaller, in six male-to-female transsexuals whose brains were examined post-mortem.
Dr Swaab said yesterday: "Transsexuals are right that they feel different. There is something different about them." He said society should accept transsexuals' requests to have their birth certificates and passports changed to reflect what they feel to be their true gender. Holland permits official documents to be changed after someone has had a sex-change operation.
Dr Swaab found that the difference in the brain persisted regardless of the person's sexual preferences. It is related solely to whether one feels oneself to be male or female.
The discovery, reported in today's issue of Nature, confirms that the most important human sexual organ is the brain. In the US, the neuroscientist Simon Le Vay showed in 1991 that a region of the brain related to sexual preference was smaller in women and homosexual men than in heterosexual males.
Earlier this week, other US researchers claimed they had confirmed there are genetic differences between male heterosexuals and homosexuals.
But Marc Breedlove, a neurobiologist from the University of California, said the lay public should not "assume that a structural difference in the brain is the immutable signature of purely biological forces".
Only if a difference between the genders were found in newborn or foetal brains could it safely be ascribed to non-social factors, he said.
Dr Swaab rejected a genetic cause, saying: "There is no indication that it runs in families."Reuse content