Why did the pope say gender is a property of essence? In his 2012 Christmas address, Pope Benedict XVI said:


  According to the biblical creation account, being created by God as
  male and female pertains to the essence of the human creature.


The use of the word "essence" puzzles me here. I wonder whether gender is a property of essence or existence. Does gender still exist in Heaven? Isn't gender a property of the body rather than an attribute of each being?  If so, gender is tied to existence. What is official Catholic teaching on this?
In his teaching, The Theology of the Body, Pope John Paul II argues that the essence of being human is both body and spirit.  He asserts that a human spirit without a body is as much an aberration as is a body without a spirit.  Therefore, either without the other is not entirely human.

He makes the very good point that Jesus was raised bodily, and that Paul taught that we will be raised bodily, that indeed that Christian afterlife is a translation into another realm of material existence and not a purely spiritual one.

He also makes the argument that gender is an essential aspect of what it means to be human.  We will not be raised genderless, but as male and female.  Jesus taught only that there will not be marriage in heaven, not that there would not be male and female. According to JP II the reason for that is because we will be experiencing the fullness of relationship that the Trinity share and the marital relationship, being simple a fore-shadowing of that unity with God, will be superfluous.

So all of that to say, yes, as I understand John Paul II's teaching, our sexuality (but not the sexual act) is essential to our being as humans.  That is, to be perfectly clear, sexuality, that is the state of being male or female is, according to JP II (and I agree), essential to being human; the expression of love in sexual intercourse may not be.  The latter may only be a temporal sign of the marriage of Christ and the Church which will be redundant in the eternal state.