How did birds like penguins evolve into some of the world's best swimmers?

Engineers explain how birds like penguins evolved into such incredible swimmers.

This is an Inside Science story.

The ancient ancestors of penguins gained their ability to swim at the expense of flight, engineers found.

They mathematically compared the swimming efficiency of penguins to the movements and propulsion of birds like puffins and guillemots that haven't lost their ability to fly but can still swim for brief periods while foraging underwater.

"It's kind of an engineering method to look at species as highly sophisticated engines," said Peter Dabnichki, a professor of mechanical engineering at the Royal Melbourne Institute of Technology in Australia. "Basically we tried to understand how flapping wings work in the water."