Q: Bisexuality: (82:0.1) and (87:5.2)—implies bisexualtiy is the biologic norm, and marriage is the social response to managing this—is that correct?
A: It's always helpful to consider not only the context of what's written but the historical perspective of the words used. In the instances here, the topic of Paper 82 is the evolution of marriage and Paper 87, ghost cults. Clicking on these links will open up the text of the references you cite. In the nearly 80 years since the text of The Urantia Book was written both the culture and the language have evolved....we say and do things today that weren't said or done at that point in history and therefore, to understand what's being related we actually have to make ourselves sensitive to historical context.
Bisexuality means two sexes, which is the norm for material sex creatures in the created universe. Marriage between a man and a woman is the norm in social evolution since it becomes the foundation for the family, the stable base for the rearing of children and the continuing evolution of culture.