Pregnant women may wobble but they don't fall down: Mystery solved

Despite often having to deal with an offcentered load, most pregnant women are remarkably stable. They don't seem to fall with any more regularity that non pregnant females.

Scientists have discovered that about 2 million years ago the spine in women gradually evolved to be more flexible and supportive than in men. This in turn allwed thier bodies to adapt during pregnancy. The changes were nessesary to evade predators and forage for food while pregnant. Those that did not have the variation quickly sucumbed to darwinian processes

news.yahoo.com...

Interesting that it is only bipeds, and a shame only females: I could use the back support for my beer gut.