Here, the aviators are reptiles too. They begin as little flapping things the size of a mouse, barely larger than the insects they so gamely attack on the wing. Nesting sites are few and far, and so they form jostling, screeching colonies wherever they can lay their eggs safely. Like many bird species in other branches, they are shoehorned into socialization by the sheer necessity of putting up with the neighbours. Defending their eggs from predators and peers who want their land leads to strong pair bonding and egalitarian parental care. Each generation spends longer in the nest and learns more from their parents. They learn flight, what to eat, how to interact with others. They learn that this sound means danger, that sound is a challenge, this other is an entreaty. Soon enough, a language.

Fortune favours bigger brains and bigger wings. To a human eye the creatures they become are goblinish: stick-thin limbs wrapped in leathery cloaks of patagia, one long finger swept back behind them like a gentleman’s sword even as the other clever digits are at work building nests or working stone. Their heads are outlandish, too large for the rest of them—pushing the physics of flight to the limit to allow for more thought.

In this parched world, the desert is a riot of thermals to aid them in expeditions, and below are a thousand ecosystems that can never breed a predator to threaten them. They skewer swimmers with barbed sticks, winkle burrowers from holes. They bring larger animals down with rocks dropped from a height and butcher them with sharp stones.

In our own far more recent history, a clever kind of upright ape broke nodules of flint apart—creating keen, serrated edges to take apart the world. It was a fundamental building block of our success, and yet for a long time there was no more to it than that. When our handy ape ancestors had finished with the task, they finished with the tool, discarded it into the brush. Next time they would knap a new one from whatever was at hand. There is a place in our minds now that tools—made things, things of value—occupy, and there was a time when our ancestors’ minds had no such place. Nothing was ever for keeps, and there was no tomorrow for the tool-makers.

The pterosaurs have the same limitation, but ruthlessly imposed by physics. They can make things quickly, envisage what tool they need for what task, but they cannot carry a toolkit around. If they hunt, then their little capacity must be saved for the prize, not the means of getting it. They are trapped in a cycle of transience, and their technology is limited by what they can make here and now. Perhaps one of them thinks, every so often, Did I not have a better stone last time I did this? If only I had that stone today…