Like hippos, their closest living relatives, whales are descended from an ancestor that had four legs and walked on land, a transition explored in the upcoming exhibition Whales: Giants of the Deep, opening March 23.

It's Darwin Day, 2013, and readers around the world can digitally peruse scientific manuscripts Charles Darwin wrote, thanks to the Darwin Manuscripts Project at the American Museum of Natural History, directed by David Kohn. 

In the late 1960s, Curator Emeritus Niles Eldredge was a graduate student with a passion for trilobite eyes. He had been taught to expect slow and steady change between the specimens of these Devonian arthropods he collected for his dissertation. Only his trilobites were doing one of two things: staying the same, or evolving in leaps.