Penguins evolved from birds that didn’t need to fly and so their wings changed and now penguins can’t fly. Wings and your ability to fly. Use it or lose it.
On the other hand, flying fish escape predators by leaping out of the water, flying for several yards, and reentering the water at a safer place. This is nothing short of amazing. This is the opposite of “use it or lose it” that we don’t hear about much. The rhymes don’t work out as well but it’s something like “Grow it and show it.” If you need it, you should breed it.
Before birds like penguins lost their ability to fly, there was some wingless creature walking around, wishing it could fly. And then it grew some wings.