Did they? Did they really? Evolve something for a certain purpose, is that even possible? Did the 'good old boys' of the dinosaur age sit down one evening and have a conversation about it..
*that wiggly thing that shows there is about to be a flashback*
T.Rex : I'm getting so fed up, I never seem to get a girl friend these days, my short arms put them off.
Allosaurus : man I know what you mean, I tried to take out an ankylosaurus and she just wanted to go clubbing with her girl friends, not interested in coming back to my place at all
T.Rex : seriously dude we are gonna go extinct if we don't get some loving soon.
Avaceratops : (butting in) look at the tail on that Apatosaurus!
T.rex : shut up, concentrate how do we improve our chances!?
Allosaurus : we should grow some feathers, I saw an Ornithomimosaur down at the tar pit, he's evolved feathers and the babes were all over him!
T.Rex : ok lets give it a go, lets grow feathers, grab your coats - lets pull!
*wavy thing again, we are back in the present*
So I think maybe they didn't evolve something 'for' something. I think maybe feathers happened, like weird stuff does, and those lady dinosaurs just liked it...so the males got lucky more.
Any way, this is why I'm not a scientist.
