At conception we either are xx - female or xy- male genetically. however, the body starts out physically as female and is then modified or not due to the influence of hormones. we also go through all the stages of evolution before we start to look like people. the very early embryos of all species look very similar to one another.  at one point in your existance in this world and life you had gills and a tail. at one point you were a single celled organism, at one point you were a simple tube. Perhaps we can embrace this concept as a spiritual connection to all life?
Dualism is a difficult concept to shed because we do tend to define the world by it. Hence the problems when we think of gender as an either/or situation. Gender is a spectrum, though most people do not think about it that way. I have learned a lot about it from dear friends that are gay, bi-sexual, transgender and hermaphrodite. Before I knew these people, it never occured to me that there may be more to gender than boy and girl. It also made me start thinking about other so called 'absolutes' in life and how maybe I needed to think a little more deeply about those as well.

http://www.pbs.org/wgbh/nova/gender/fs.html

Just an article for those interested.