How porn evolved

From The Economist: "Ever since Palaeolithic humans worked out how to paint and carve, new media have been used for sexually explicit representations. Some of the earliest photographs and films depicted disrobing or nude women. But they were pricey: in the mid-1800s, before the advent of negatives and half-tone printing, a photo of a naked prostitute cost more than engaging her for sex. Not until 1953, when Hugh Hefner launched Playboy with a nude photograph of Marilyn Monroe, did porn go mass-market."