Women in Science and Technology:

>Although women’s representation in many scientific fields is lower than that of men, it is not uniformly low. Rather, it varies widely from field to field. It is a reasonably accurate generalization to say that the ‘softer’ the scientific field, the higher the frequency of women. In the U.S., for example, women in 2002 earned 16 per cent of physics doctorates, 18 per cent in engineering, 29 per cent in mathematics, 34 per cent in chemistry, 45 per cent in biology, and 67 per cent in psychology (National Science Foundation, 2003). In the social sciences, women are relatively scarce in economics but abundant in anthropology and sociology. Even within fields, there is marked differentiation by subfield.Women earn relatively few doctorates in mining/mineral engineering, biophysics, and psychometrics, but considerably more in bioengineering, nutritional sciences, and developmental and child psychology.

... The fields in which women are scarce tend to have the lowest social dimension, while those attracting larger numbers of women tend to have a higher social dimension. Lubinski, Benbow, and Morelock (2000) have characterized this distinction as being between the ‘organic’ and the ‘inorganic.’ The fields avoided by women tend also to be the most mathematically and spatially demanding. Given the relative positions of the sexes on the ‘people-things’ dimension and the abundance of men at the highest levels of mathematical ability, it would be surprising not to find differing sex ratios in these widely differing fields, at least if people sort into occupations based upon their interests and abilities.<

K. R. Browne, Evolved sex differences and occupational segregation, 2006
http://faculty.law.wayne.edu/browne/Documents/Articles/Evolved%20Sex%20Differences%20and%20Occupational%20Segregation_Browne.pdf