Men Don't Have Backbone for Pregnancy (No, Really)

We’re just sayin’ …

Heidi Ledford writes at Nature News:

The next time you see a pregnant woman teetering under the awkward weight of her growing belly, remember this: if she were a man, it would be even worse.

Researchers have found that the vertebrae that make up a woman’s spine have evolved to give her more support, probably to help her cope during pregnancy. The results hold true for modern mothers as well as those of their ancient ancestors, Australopithecus, who lived more than two million years ago. Vertebrae in men lack these features.

Without this added support, women would have to draw more on their back muscles to stay upright. Over the course of nine months, that could lead to muscle fatigue and back injury.

The study involving 19 pregnant women was conducted by Katherine Whitcome and Daniel Lieberman of Harvard and Liza Shapiro of the University of Texas at Austin, and the findings were published in this week’s issue of Nature. A summary is available without registration.

Here’s more from the Boston Globe:

The female-male difference in spinal curvature does not appear in chimpanzees, meaning it was an adaptation that occurred after human ancestors started walking upright – a fact of significance for understanding human evolution.

“This broadens our understanding of how our success as a species came to include the vertebral column,” Whitcome said. “These changes not only made females more comfortable, they provided an evolutionary edge.”