"Physicists studying the flight of the fruit fly have concluded that the tiny creature's wing motions are much closer to the movement of swimming organisms than previously thought. This surprising result lends credence to the controversial suggestion put forward by some evolutionary biologists that flight could have evolved gradually from swimming as life left the oceans.
The wings of birds and insects are structurally quite similar to the fins and paddles of aquatic animals. However, flying and swimming seem to involve completely different physical processes. Flying organisms propel themselves using the lift forces generated as a wing slices through the air, while swimming organisms paddle forward using the viscous drag of water. As a result, some biologists have doubted that flight could have evolved from swimming."
