Why did God create man male and female?
God, who is love and the archetype of community, created man male and female so that together they might be an image of his nature.
God made man in such a way that he is male or female and longs for fulfilment and completion in an encounter with the opposite sex. Men and women have absolutely the same dignity, but in the creative development of their masculinity and femininity they give expression to the different aspects of God’s perfection. God is not male or female, but he has shown himself to be both fatherly (Luke 6:36) and motherly (Isaiah 66:13). In the love of man and woman, especially in the community of marriage, in which man and woman become “one flesh” (Genesis 2:24), people are privileged to sense something of the happiness of the union with God in which every man finds his ultimate wholeness. Just as God’s love is faithful, so also their love seeks to be faithful; and it is creative, as God is, because from marriage new life comes forth.
From the Catholic Youth Catechism (Question 64)