Natural Selection Is Hard to Measure

Charles Darwin's idea that an unguided natural process led to all the beauty and diversity of the world, including its Undeniable appearance of design, guides scientific thinking to this day. But what if his signature mechanism -- natural selection -- cannot be measured? Without measurement, a theory reduces to anecdote. A recent paper in the Proceedings of the National Academy of Sciences threatens to do that, at least in regard to "the evolution of human body form." The implications go far...