I find this subject provided shows some valuable insights, especially into why we differ in what we look for in a partner. It’s a little complex in places, but if you are really interested in learning more about yourself and your friends it is worth printing it and reading it in slow time.
It might help put in terms some of the fears and questions we all really have under the fun and frivolity. It might also stop us from attacking one another for being different!
Subject: the Five-Layer Model of Gender
This is the best explanation I have ever found of gender from the medical profession, apologies if you have already read it.