So, it occurred to me: if chickens (and some other birds) have wings but cannot fly,
Dont know if this helps but...
As I understand it the domestication of chickens is what attributes to their current flightless abilities. One would have to know the history of the modern chicken to know that had it not be for this domestication the chicken could very will be a bird of flight.
Genetic evidence shows that the chicken is family of the junglefowl, which is of the pheasant family, which do fly.
Selection pressure could also add to the inability to fly. Species who are newly flightless may show signs of being better equipped for flight since they would be close to the seperation from flight to flightless but would still be flightless none the less. However, it has been a while since I've read up on the evolution of flight so I'm speculating.
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