Feathers probably evolved for insulation in flightless dinosaurs, but they turned out to be useful for flight in birds, the dinosaurs' descendants. Feathers are considered _________ because feathers did not evolve for that purpose.

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Quizplus · Accepted Answer

Feathers are considered by-products in this context because they originally evolved for insulation, not for flight, indicating they were not initially an adaptation for flying but became useful for that purpose later.

Feathers Probably Evolved for Insulation in Flightless Dinosaurs, but They