My Year of Darwin 4/14/2014: Shared but not shared

"Thus we find in South America three birds which use their wings for other purposes besides flight; the penguin as fins, the steamer as paddles, and the ostrich as sails." Charles Darwin, Voyage of the Beagle

Homologous features exist as a result of common ancestry and can take on various roles in different lineages. Darwin doesnt state this explicitly but i know he's thinking about it.

Written on my phone.  Not easy.