As a digression, this insular attitude results in a rare moment when two separate species exist side by side on the Earth, both able to claim a measure of awareness and sentience. Around the equator are great fern and cycad forests, where dwells a species of colonial spider that has been evolving a mind of a very different kind. The forests are dense with their webs, which form an extended sense organ linking all the component parts of the colony. Later, these generations-old and constantly rewoven tapestries become a kind of exported cognitive engine. The spiders do not think, but between them the web they work on becomes a substitute mind—active when they move upon it and update it, falling to oblivion should they ever stop. And when the great tropical storms come to lash the equatorial forests, these weird minds are torn apart and die, and the spiders blindly weave fresh webs the next season until a new thinking being is born, knowing no continuity with what was lost. The Devonians observe this but can only tell that after the webs hit a critical mass of complexity, the conduct of the colony becomes abruptly more purposeful. It seems to be planning ahead beyond the dreams of any of the individual weavers.

Perhaps it is this observed outsourcing of intellect that prepares the Devonians for what must happen next.

It is their ill luck to rise to prominence in the very shadow of obliteration. Even as they perfect their icy difference engines, the world is turning. The continents are already clasped in their death knot; volcanic traps the size of continents vomit poison into the air and sea. The ice that nurtures their civilization retreats north and south; the cold water is warmer each summer. They begin to smother, then boil.

The great dying time, the Permian extinction, is upon them too now, and they are an especially susceptible species. Their thinkers, their scientists and engineers and fish-eyed dreamers, come together to croak and rumble out their theories and plans. They are, after all, masters of their world. Surely there is something they can do? With the aid of their great computers they determine that there is. There are many things, in fact, and they will do all of them. In desperation they set out to wrestle Death for the fate of the world.

United as a species working to the limits of its technology, they fight the warming of their planet at every turn. They alter the currents of the seas, seed clouds with ice and grow structures within the ice caps that alter Earth’s weather patterns beyond recognition. They launch countless more composite satellites into orbit, forming mirrors to parry the rays of the sun. They plant inland mountains with glaciers and accelerate their growth artificially until the ice fields themselves become their armies, marching across the barren land in savage wars of attrition. The Devonian civilization will not go gracefully into anybody’s fossil record.