Evolution Goes Wild in Once-Polluted Lake

May 15, 2008 -- The cleanup of a polluted Washington lake appears to have driven evolution backwards for the threespined stickleback fish living there.

Marine-dwelling versions of these fish are covered in bony plates, but as sticklebacks migrated into freshwater, a strong selection pressure caused them to lose their armor.

But comparing genetic patterns in fish from the sound with those in the lake showed migration of plated marine fish into the lake was not enough to account for the shift.

"We would love to have fish from the 1900s before the ship canal was built," Peichel said.