A Walk Through Water Before Reaching Land

"While biologists have long thought that the digitized limbs came first, followed by the move to a terrestrial habitat, new research suggests a different sequence. “It’s possible that walking evolved before feet or hands or digits or toes — or even being on land,” said Heather King, a biologist at the University of Chicago and a member of the research team, whose work appeared in Proceedings of the National Academy of Sciences. Ms. King and her team studied the movement patterns of an African lungfish, a modern-day lobe-finned fish that shares many features with the ancient precursors of the tetrapods: It has four nondigitized fins, lungs and no sacrum — the triangular bone that joins the hips to the spine and, in tetrapods, conveys energy from a stepping leg to the rest of the body. The team observed a few fish taking alternating steps with their rear fins along the bottom of a test aquarium or pushing off with both rear fins at the same time in a hopping motion. Even though the fish lack a sacrum, Ms. King suspects they are able to push themselves forward because their lungs make them buoyant."
  By RITCHIE S. KING / The New York Times