Failures

The People Of The Wind, IV.

On Ythri, probably:

warm-blooded organisms evolved directly from amphibians, not from reptiloids;

successful land animals lost their gill;

"More primitive animals kept it." (p. 482);

one primitive animal left the swamps, climbed trees and glided with a membrane;

the membrane became a wing;

the gill became a supercharger for aerial use;

hence, Ythrians.

"'As usual,' Wa Chaou observed. 'The failures at one stage beget the successes of the next.'" (p. 483)

See also Mountains And Boat.