Nature's Back-Up Plan Keeps Pregnant Women Upright

Scientists have found slight differences in the lower back and hip joints of men and women—results of evolution—that help women keep their balance and avoid serious back pain while pregnant, the AP reports. “(Women) are experiencing a pretty impressive challenge. Evolution has tinkered ... to the point where they can deal with the challenge," a Harvard anthropology researcher said.

The study found that women have a differently shaped lower vertebra and a larger hip joint, which helps them adjust their center of gravity and carry extra belly weight. Researchers believe the changes are evolution’s way of compensating for walking on two feet. "It's absolutely beautiful," one said. "A little bit of tinkering can have a profound effect." (More evolution stories.)