"Love" is a bad word to use in this instance. I love my son, my parents, my siblings, my friends and I don't think I could put them all into those 3 "forms".
And no, I don't think humans are physically monogamous, I think you have to be monogamous spiritually - it's your heart and brain that keeps you from straying.
And the fear of getting your ass whooped by your spouse's attorney. :P