The reptiles had chosen the slow, collective option. In their early times, they had played a lot on many variations, and things like growing fins on one’s back, or a disproportionate neck, was considered at worst as amusing whims. So: trying to fly? Suit yourself. Alright, happenstance cut this approach short, and seriously upset climatic conditions, and a great number of prototypes from this time were lost forever.
But chief among the qualities of reptiles is assuredly is their coolheadedness. Did the catastrophe upset them? Nope. They just changed their tactics. Goodbye to haphazard additions, hello to progressive, mass-tested modifications. Once they grasped the laws of squares and cubes, they began to reduce their size. For most of them, their front legs were already too short for catching things, so they gradually stretched them out (the feathers were a happy coincidence).
Eventualy, the reptiles turned birds reached the ability to leave the ground… only to find that they had based their whole strategy on the continuous presence of air. But air, which had its own opinion on the matter, had huddled into a thin film around the planet, so that our birds were not likely to go much further this way.
Terrestrial mammals, who had proliferated upon the misfortunes of reptiles, adopted another strategy based on two angles. On the one hand, rather than adapting to their environment, they started adapting the environment. Realizing that to get off the planet they had to propel themselves fast and hard, and quickly convinced that their muscles alone would not be enough, they built machines to push for them. On the other hand, instead of trying to get everyone to fly a little, they opted to get a few of them to fly a lot. The approach paid off, for soon a handful of them were able to leave the atmosphere and take a few uneasy steps into space, but most of them had to return to the ground (and the few who did not return could not, with the best will in the world, be stated as “having freed themselves from their homeland”).
Hands-down victory, however, went to the whales.
They were first seen leaving the depths, swiming near the surface, in unusual straight lines. Then they slowly emerged while still moving forward. Some went out to sea, others straight towards the coast. They wer witnessed lazily overhanging seaside residences, flying inland, following old railway tracks for a while, and, for some, even drifting, nonchalantly, between buildings in some cities. But above all, gradually, they were rising. The sky was studded with blue spots of various sizes depending on the distance, but they all rose, shooting stars upside down, faster and faster, farther and farther away, smaller and smaller, until they all disappeared.
And no one ever found out how they’d done it.