Narrator: This is Science Today. American women have a 1 in 2 chance of fracturing their bones after the age of 50. In fact, osteoporosis is almost expected in older women. But biological anthropologist Sabrina Agarwal of the University of California, Berkeley, says fragile bones are a relatively recent phenomenon. Agarwal studies skeletons from ancient populations to understand diseases such bone loss and osteoporosis.
Agarwal: One of the things that we've seen is that when we've looked at all kinds of different historical and prehistoric populations is that bone loss really depends on what's going on in terms of all these other factors — what you're eating, what you're doing.
Narrator: In one past population in rural England, Agarwal discovered that women experienced bone loss gradually during their reproductive years and those 50 or older had little or no bone fragility.
Agarwal: I think part of that's because they've had this dramatically different hormonal environment all their lives. And so the women that do go on to old age have had this very dramatically different hormonal environment, so that when they hit menopause, they don't have the big plummeting drop that we do.
Narrator: For Science Today, I'm Larissa Branin.