If you knew then why did you ask? That violates discourse ethics to give if not request information.
Familial relationships evolved. A lot of that evolution is dependent on the woman bearing the long burden of birth to allow the baby enough development time to survive. Then there is the care after the baby is born. Men as mates who would form a long-lasting monogamous relationship would be selected for evolutionarily. thus is the beginning of the family. Add to that division of labor and specialization. Anthropologically these are all the beginnings of civilization.
Some good reads that delve into this and explain it far better than I can are Haidt's The Righteous Mind, Wright's The Moral Animal, and Ridley's The Rational Optimist.
Tradition is not the worship of ashes, but the preservation of fire. ― Gustav Mahler
WORK AND FIGHT FOR THE REVOLUTION AND AGAINST THE INJUSTICE.