When the water was gone, it got so hot that the carbon dioxide was baked out of the rocks. Under air as dense as an ocean, the dried seabeds grew hot enough to melt lead. Even the thermophiles wilted. It was the last extinction event of all.
But on rocky ground as hot as the floor of an oven, the bacteria had left behind desiccated spores. In these toughened shells, virtually indestructible, the bacteria, dormant, rode out the years.
There were still convulsions as asteroids and comets sporadically fell onto the parched land, more unremarked Chicxulubs. Now there was nothing left to kill, of course. But as the ground flexed and rebounded, huge quantities of rock were hurled into space.
Some of this material, taken from the edge of each impact zone, was not shocked, and therefore it reached space unsterilized. That was how the bacterial spores left Earth.
They drifted away from Earth and, propelled by the gentle, persistent pressure of sunlight, they created a vast diffuse cloud around the sun. Encysted in their spores, bacteria were all but immortal. And they were hardy interplanetary travelers. The bacteria had coated their DNA strands with small proteins that stiffened the helical shapes and fended off chemical attack. When a spore germinated it could mobilize specialized enzymes to repair any DNA damage. Even some radiation damage could be fixed.
The sun continued its endless circling of the Galaxy’s heart, planets and comets and spore cloud and all.
At last the sun drifted into a dense molecular cloud. It was a place where stars were born. The sky was crowded here; dazzling young stars jostled in a great swarm. The fiercely hot sun with its ruined planets was like a bitter old woman intruding in a nursery.
But, just occasionally, one of the sun’s spaceborne spores would encounter a grain of interstellar dust, rich with organic molecules and water ice.
Battered by the radiation of nearby supernovae, a fragment of the cloud collapsed. A new sun was born, a new system of planets, gas-stuffed giants and hard, rocky worlds. Comets fell to the surface of the new rocky planets, just as once Earth had been impact-nourished.
And in some of those comets were Earthborn bacteria. Only a few. But it only took a few.
Still the sun aged. It bloated to monstrous proportions, glowing red. Earth skimmed the diffuse edge of the swollen sun, like a fly circling an elephant. The dying giant star burned whatever it could burn. The final paroxysms lit up the great shell of gas and dust that lingered around the sun. The solar system became a planetary nebula, a sphere shimmering with fabulous colors, visible across light-years.
These glorious spasms marked the final death of Earth. But on a new planet of a new star, the nebula was just a light show in the sky. What mattered was the here and now, the oceans and the lands where new ecosystems assembled, where creatures’ changing forms tracked changes in their environment, where variation and selection blindly worked, shaping and complexifying.
Life always had been chancy. And now life had found ways of surviving the ultimate extinction event. In new oceans and on strange lands, evolution had begun again.
But it had nothing to do with mankind.
Exhausted, dust-laden, her body covered by a hundred minor scrapes, bruises and prickles, her baby cradled in her arms, Ultimate limped to the center of the ancient quarry.
The land seemed beaten flat, with the sun poised above, a great glowing fist. And at first glance there was no sign that anything still lived on this desert world, none at all.
She approached the Tree itself. She saw the big pendulous folded-over shapes of cocooned people, inert and black. The Tree stood there, silent and still, neither reproving nor forgiving her small betrayal.
She knew what she had to do. She found a folded-up ball of leaves. Carefully she prized the leaves open, shaping them into a makeshift cradle. Then she placed her baby carefully inside.
The baby gurgled and wriggled. She was comfortable, here in the leaves; she was happy to be back with the Tree. But already, Ultimate saw, the belly-rope had snaked into its orifice in the child’s stomach. And white tendrils were pushing out of pores in the cradling leaves, reaching out for the baby’s mouth and nose, ears and eyes.
There would be no pain. Ultimate had been granted that much knowledge, and comfort. Ultimate stroked the child’s furry cheek one last time. Then, without regret, she folded up the leaves and sealed them up.
She clambered off the ground, found her own favorite cocoon, and snuggled inside, neatly closing up the big leathery leaves around her. Here she would stay until a better time: a day miraculously cooler and moister than the rest, a time when it might be possible for the Tree to release Ultimate from this protective embrace, to send her out into the world once more — even to seed her belly with another generation of people.
But there would never be another impregnation, never another birth, never another doomed child.
One by one the cocoons would shrivel as their inhabitants, sealed in green, were absorbed back into the bulk of the borametz — and in the end the borametz itself, of course, would succumb, thousands of years old, tough and defiant to the last. The shining molecular chain that had stretched from Purga through generations of creatures that had climbed and leapt, and learned to walk, trod the dirt of another world, and grown small again, and mindless, and returned to the trees — at last that great chain was broken, as the last of Purga’s granddaughters faced an emergency she could not withstand.
Ultimate was the last mother of all. She couldn’t even save her own child. But she was at peace.
She stroked the belly-root and helped it worm its way into her gut. The Tree’s anesthetic and healing chemicals soothed her aching body, closed her small wounds. And as psychotropic vegetable medications washed away the sharp, jagged memory of her lost baby, she was filled with a green bliss that felt as if it would last forever.
It wasn’t such a bad way for the long story to end.
Epilogue
There had been a sighting of another band of feral kids, this time on Bartolome Island. So Joan and Lucy had loaded up the nets and tasers and hypo rifles, and here they were limping over the Pacific in their sun-powered launch.
The flat equatorial sunlight reflected off the water onto Joan’s pocked skin. She was fifty-two now but looked a good deal older, such was the damage that had been done to her skin, not to mention her hair, by the environment she had endured since Rabaul. But Lucy had met very few truly old people in the course of her short life, and she had few points of comparison; to her, Joan was just Joan, her mother, her closest companion.
The day was bright, the few clouds high and streaky. The sun beat hard on the big solar cell sail spread over Lucy’s head. Still, they had packed their heavy-duty ponchos, and every few minutes the women glanced at the sky, fearful of rain that might wash down more of the high dust onto them, the toxic, sometimes radioactive grit that had once been fields and cities and people that was now wrapped around the planet like a thin gray blanket.
And, as always, Joan Useb talked, and talked.
“I always had a soft spot for the British, you know, God rest them. In their heyday they didn’t always behave well, of course. But the human story of the Galapagos was otherwise pretty unhappy: mad Norwegian farmers, Ecuadorian prison camps, everybody eating the wildlife as fast as they could. Even the Americans used the islands as bombing ranges. But all the Brits did to the Galapagos was send over Darwin for five weeks, and all they took away was the theory of evolution.”
Lucy let Joan’s chatter wash through her head, these random echoes from a world she had never known.