So does this mean men with big beer bellies are tippy?

I don't know, I'm just asking. After all, this study presumes women have evolved to better handle the front loaded abdominal weight of pregnancy.

Pregnant women do not tip over, and the reason has a lot to do with an evolutionary curve, researchers say.

Anthropologists studying the human spine have found that women’s lower vertebrae evolved in ways that reduce back pressure during pregnancy, when the mass of the abdomen grows by nearly a third and the center of mass shifts forward considerably.

Even without the benefit of advanced study in biomechanics, women tend to deal with the shift — and avoid tumbling over like a bowling pin — by leaning back. But the solution to one problem creates another, since leaning puts even more pressure on the spine and muscles.

And that, report researchers from Harvard and the University of Texas in the current issue of the journal Nature, is where evolution enters the story.

Anthropologists have long known that the lower spine in humans developed a unique forward curve to help compensate for the strains that arose when the primate ancestors began walking upright. Researchers looked for a mechanism that compensated for pregnancy’s additional burden as well.

What they found, said Katherine K. Whitcome, a post-doctoral fellow at Harvard and the lead author of the paper, was evidence that evolution had produced a stronger and more flexible lower spine for women.

So by this logic, when I head out to the malls to finish my Christmas shopping, I should be seeing massively beer bellied men spontaneously tipping over left and right like those scare goats that pass out when startled. After all, men don't have the evolutionary advantage that women have in this regard. Right? If so, maybe it is time to ban Santa due to the tipping hazard he presents around small children.