Carl Sagan famously said "we are all star stuff" in his 1980s TV series Cosmos. The stuff theme stuck. Lawrence Krauss wrote in New Scientist for February's Darwin Bicentennial that we should all "celebrate evolution as only star children can." He said, "Since the days of Galileo, astronomy has established a fundamental connection between humans and the cosmos.

Evolution, the concept that each type of animal arose from some other sort of animal, faces many daunting challenges. Among the more difficult hurdles for evolution to clear is the formation of turtles from non-turtles, and the development of snakes from non-snakes. Darwin was fascinated by them both, and openly wondered what path they took on their evolutionary journey.

by Brian Thomas, M.S. and Frank Sherwin, M.A.*