The colorful extravagance of some birds, the deliberately excessive horns, manes, and tusks of some mammals, the complex courting behavior of many animals, the very existence of sex itself - and by extension the love songs on the radio, and all the love-addled poems ever written - all likely evolved because of parasites, because all organisms must run as fast as they can just to stay in place. - Moises Velasquez-Manoff “An Epidemic of Absence”