why can't penguins fly

Penguins can't fly mainly because their wings evolved to be strong, short, and stiff flippers adapted for swimming rather than flying. Unlike flying birds, penguins have dense bones (which are heavier than the light, hollow bones of flying birds) and bodies built for diving and swimming at high speeds underwater rather than for flight through air. Their wing bones are fused straight, making the wings rigid and powerful paddles for efficient underwater propulsion, but unsuitable for generating lift in the air. Over millions of years, penguins lost the ability to fly as an evolutionary trade-off to become better swimmers, enabling them to dive deeper, swim faster, and stay underwater longer to catch prey in aquatic environments where they live and feed.