There’s a unity to life. Sometimes it’s plain to see, but very often it lurks underneath a distraction of differences. And a  new study shows that there’s even a hidden unity between our slipped disks and the muscles in a squirming worm.

Scientists call this unity “homology.” The British anatomist Richard Owen coined the term in 1843, sixteen years before Charles Darwin published The Origin of Species.  Owen defined homology as “the same organ in different animals under every variety of form and function.” For example, a human arm, a seal flipper, and a bat wing all have the same basic skeletal layout. They consist of a single long bone, a bending joint, two more long bones, a cluster of small