Imagine whales on land - what once was

Researchers have revealed the genetic basis behind one of the best-documented examples of evolutionary change in the fossil record: how whales lost their hind limbs. Writing in this week's Proceedings of the National Academy of Sciences, scientists report that ancient whales - four-footed land animals not unlike large modern dogs - evolved into graceful, streamlined swimmers through a series of small genetic changes during the whales' embryonic development.

A gene called "Sonic Hedgehog," named by a creative scientist, was in effect between 41 million and 50 million years ago when whales' hind limbs shrank greatly as the former land animals began a return to the sea. But their legs showed no change in the basic arrangement and number of bones, which proved that Sonic Hedgehog was in effect. Read more great science findings at the National Science Foundation.