Anthropologist Liza Shapiro and two fellow researchers won an Ig Nobel Prize — dedicated to “achievements that first make people laugh, and then make them think” — for a 2007 study on the evolutionary reasons pregnant women don’t tip over. By studying 19 pregnant women, they discovered that a woman’s lumbar, or lower back, curve extends across three vertebrae. In men, it extends across two. The joints between the vertebrae also are larger in females and angled differently to better support the extra weight.
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