The history of straightness is much shorter than you’d think. An expert explains its origins

If you met Hanne Blank and her partner on the street, you might have a lot of trouble classifying them. While Blank looks like a feminine woman, her partner is extremely androgynous, with little to no facial hair and a fine smooth complexion. Hanne’s partner is neither fully male, nor fully female; he was born with an unconventional set of chromosomes, XXY, that provide him with both male genitalia and feminine characteristics. As a result, Blank’s partner has been mistaken for a gay woman, a straight man, a transman — and their relationship has been classified as gay, straight and everything in between.

Blank mentions her personal story at the beginning of her provocative new history of heterosexuality, “Straight,” as a way of illustrating just how artificial our notions of “straightness” really are. In her book, Blank, a writer and historian who has written extensively about sexuality and culture, looks at the ways in which social trends and the rise of psychiatry conspired to create this new category in the late 19th and early 20th century. Along the way, she examines the changing definition of marriage, which evolved from a businesslike agreement into a romantic union centered around love, and how social Darwinist ideas shaped the divisions between gay and straight. With her eye-opening book, Blank tactfully deconstructs a facet of modern sexuality that most of us take for granted.