Mice and men

Mice lacking oestrogen do not show aggression

source: New Scientist December 2 2000 p23

Male mice lacking an enzyme which turns male hormones into oestrogen do not exhibit aggression when their territory is encroached on by other mice, Japanese researchers report. This changed if the mice had oestrogen supplements just after they were born, though they were not aggressive if there was a delay until seven days after birth before they had oestrogen supplements. The research was carried out at Japan's Kochi Medical School, and is to be reported in 'Journal of Endocrinology'.