Altering a mouse's sense of smell can seriously mess with its gender identity

http://discovermagazine.com/2007/sep/girls-gone-boys-gone-wild
Altering a mouse's sense of smell can seriously mess with its gender identity

...life may not be quite that simple—at least for mice. A new study in Nature suggests that the brain pathways for male sexual behavior are also present in female mice, and with those pathways comes the potential for male behavior. Even more intriguing is that the activation of these pathways appears to be regulated by the animal's sense of smell.