From the beginning of creation, God made them male and female. Jesus then quoted from the second creation account, Genesis chapter two, the Adam and Eve story, part of which we heard in the first reading. For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh. From a trinitarian point of view this may be because God is relational in God s very self a trinity of persons in a unity of being and our nature reflects God s. From a scientific point of view sexual reproduction may be useful to ensure gene variation.
Partner is the key word.
Adam already has plenty of help. God his creator is certainly his helper and some of the other animals of creation are his helpers too the ox, the horse, the dog. Literally made for each other. The point is not whether such a paradise ever existed historically. The point is that this is what God intends for creation and human and divine relationships.