- Experts at Aberdeen University concluded that penguins started to 'fly' through the ocean instead of the air as they developed diving skills
- Added that birds cannot have wings that are good at flying and swimming
- Scientists studied guillemots which resemble ancient penguin ancestors
PUBLISHED: 14:51, 21 May 2013 | UPDATED: 15:02, 21 May 2013
Penguins cannot fly because they are such good swimmers - and no bird can excel at both, said scientists.
They started to fly through the ocean instead of the air as they developed wing-propelled diving skills that allowed them to forage for food at increasing depths.
The evolution of flightlessness in penguins has mystified scientists for decades.
But now a study of guillemots - which closely resemble penguins in their diving and swimming, but can still fly - shows there is no such thing as a wing that's good for both.
Scientists discovered that guillemots on Coats Island, Northern Canada, used substantially less energy than most other birds when they were diving.
But the energy they needed for flight was the highest ever reported for a flying bird - 31 times greater than expended when at rest.
Professor John Speakman, of Aberdeen University, said: 'Like many people, I wondered why on earth they lost the ability to fly.
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