- Joined
- May 31, 2012
- Reaction score
- 6,172
- Age
- 46
Short answer: because they're superior swimmers.
Prof Speakman explained: "Basically the hypothesis is that as the wings became more and more efficient for them to dive, they became less and less efficient for them to fly.
"At some point it became so 'expensive' for them to fly, that it was better to give up flying all together and make the wings into small flippers."