Rapid Deevolution Creates Lake of Fully-Armored Fish in Just 50 Years

Lake Washington, the largest lake in the Seattle area, has long been home to a soft-skinned fish called the threespine stickleback. But over the past fifty years, the lake's population of sticklebacks has changed dramatically: today, most of the fish sport partial or full body armor, a throwback to their origins as saltwater fish covered in bony plates. (In the picture here, you can see an armored stickleback on top, with plates in red; a non-armored one is on the bottom.) What caused the rapid shift in the fish's morphology? It sounds bizarre, but the mutation is the result of pollution being cleaned up in Lake Washington. A program started in the late 1960s to clear the lake of toxic sludge made the sticklebacks de-evolve. More »