22 October 2004
Male Scientists Not So Manly
by Kate Melville

A survey of academics at the University of Bath in the United Kingdom has found that male scientists typically have high levels of the female hormone estrogen. The levels of estrogen recorded are more usual in women than men, who normally have higher levels of the male hormone testosterone. The study suggests that these unusual hormone levels in many male scientists might cause the right side of their brains, which governs spatial and analytic skills, to develop strongly. The study - submitted to the British Journal of Psychology - also found that male scientists with high estrogen levels were less likely to have children and that women social scientists tended to have higher levels of testosterone, making their brains more masculine.

The study drew on other research which established that the levels of estrogen and testosterone a person has can be seen in the relative length of their index and ring fingers, the ratio of which is set before birth and remains constant. A person with an index finger shorter than the ring finger will have had more testosterone while in the womb, and a person with an index finger longer than the ring finger will have had more estrogen. The difference in the lengths can be small - as little as two or three per cent.

The survey - conducted by Dr Mark Brosnan - examined the finger lengths of over 100 male and female academics at the University. Brosnan found that men teaching hard science like mathematics and physics tend to have index fingers as long as their ring fingers, a marker for unusually high estrogen levels. It also found the reverse: male academics with longer ring fingers than index fingers - the usual male pattern - tended to be in social science subjects such as psychology and education. "The results are a fascinating insight into how testosterone and estrogen levels in the womb can affect people's choice of career and how these levels can show up in the length of fingers on our hands," said Dr Brosnan.

The research suggests that lower than average testosterone levels in men lead to spatial skills that can give a man the ability to succeed in science. This right brain development is at the expense of language abilities and people skills that men with a more usual level of testosterone develop and which can help them in social science subjects like psychology or education. Dr. Brosnan said that men with levels of testosterone very much higher than normal would also create the right hemisphere dominated brain. The extremes of low testosterone and high testosterone for men would create the scientific brain, and the normal range in the middle would create the 'social science' brain.

The research raises the question as to why more women, who have a lower level of testosterone, are not in science, which is male-dominated, with only one in 40 science professors being a woman.