First aired on The Current (22/06/12)
Thanks to modern advertising, movies and television shows, we spend a lot of time looking at breasts in our society. But do we really understand why women have breasts? And do we recognize how our environment affects them? Science journalist Florence Williams has immersed herself in the world of breasts, investigating the biology behind this complex, life-giving body part. In her new book Breasts: A Natural and Unnatural History
, she highlights some fascinating details about women's chests and some startling things she learned about her own.
"It turns out that humans have very unique breasts in the animal kingdom," Williams said on The Current recently. "All mammals have mammary glands, but in humans they are surrounded bt these particularly, what I'll call fetching packages, these rounded, sort of, attractive fatty orbs. In other primates, those fatty orbs actually disappear when you're not lactating, but in humans we have them in puberty all the way through our adult lives. And so the question is, how did we get so lucky? Why do we have these?"
Williams says there are a lot of competing theories. Many anthropologists have long believed that breasts exist...for men.
"And it sort of justifies why men are so interested in them. They think they must be conveying information somehow to a potential mate, you know, about your fertility status or your youth or health."
However, more recent anthropological research about suggests a different evolutionary purpose for breasts. It's hard to argue that lots of men enjoy female breasts, but "we don't even know if it's universal." Instead, Williams tends to side with the theory that breasts evolved to help women and their infants survive.
"The breast is mostly made up of fat," she said, adding, "humans, compared to all other primates, need a lot more fat. We need a lot more fat in order to reach puberty. We need more fat in order to gestate a baby, and then to lactate, and that's because of the unique fatty requirements of the human infant."
Williams also believes the shape of the breast evolved for the purpose of feeding children.
"The human infant, again, is incredibly unique in that it can't hold its head up for example. And so a woman has to hold the infant in the crook of her arm, and the breast sort of has to come down to meet the baby. So it's a question of ergonomics in some ways," she explained. "And of course the human palate and mouth co-evolved with the nipple, and so in the book I look to say that we really have breasts to thank for kissing."
Another aspect of the book is Williams' mission to learn more about her own breasts and how environmental factors like pollution are affecting them. To that end, Williams, who was breastfeeding her second child at the time, sent off samples of her breast milk to a research lab to test for traces of toxins. What she found was eye-opening.
"We found flame retardants, which are particularly common in North American women," she revealed. "We also found some pesticides, and incredibly, jet fuel."
In modern times, men and women have hundreds of industrial chemicals present in their bloodstreams, and most of these exist at low levels. But Williams says breasts are unique body parts in that they utilize what's in a woman's body to produce nourishment for infants.
"They sort of manage to concentrate some of these chemicals and they're masterful at converting them into food for babies. So we don't really understand what the health effects are for infants."