You certainly won’t regret reading Breasts: A Natural and Unnatural History. The historical vignettes are droll and judiciously few. “The reasons why the breasts of women are on the chest,” Henri de Mondeville wrote to the King of France in the 14th century, “whereas other animals more often have them elsewhere, are of three kinds. First, the chest is a noble, notable and chaste place and thus they can be decently shown. Secondly, warmed by the heart, they return their warmth to it so that this organ strengthens itself. The third reason applies only to big breasts which, by covering the chest, warm, cover and strengthen the stomach”. It’s like asking a three-year-old what he thinks of the sun.
There is much more uncharted territory in the world of breasts than there is mature debate, but where the latter has emerged, Florence Williams’s book makes a solid, readable précis of it. The story begins with evolutionary biology: why do we have breasts in the first place? The sex-selection theory is that breasts signify health and youth, so a man who is prepared to survey them quite closely will be less likely to waste his seed on barren ground. This might explain why men supposedly prefer large breasts, since they show the sag; small breasts, less susceptible to gravity, might lead one egregiously to suppose a 45-year-old is 35, and that’s 300 million swimmers you’ll never get back, caveman. It’s hard to falsify, especially since – unlike opposable thumbs – breasts leave no fossil record.
But there are clearly holes in the argument, since studies have shown no consistent male preference for one size over another. Furthermore, “if big, firm breasts tell a man that a woman is fertile and ready for sex, then why would her breasts be at their biggest and firmest when she’s already pregnant or lactating?” Once Williams has asked that question, almost any competing theory becomes likelier than the breast as a seed-and-time-saving signal for men. The anthropologist Gillian Bentley has developed the “flat face” theory – “in order for newborns to get through our unusually narrow bipedal hips, their faces need to be flat. Flat faces and flat chests don’t work well together.” There’s the camel theory, that breasts are fat deposits, which render a woman’s fertility and lactation more resilient to a bout of famine. There’s a theory about the specific suckling technique the breast engenders, which develops the muscles needed for speech. Williams becomes convinced – and has convinced me – that breasts evolved as a driver of female and infant survival, and men’s obsession with them arrived not “in lockstep”, but some time later. “Perhaps, all along, the breasts were calling the shots,” she concludes.