Evolution

Without the Tree’s support, such large hot-blooded mammals as Ultimate’s postpeople could never have survived so long. They were like throwbacks to easier times, out of place in this marginal environment. As the Earth warmed relentlessly, as the great desiccation continued, even the Tree-based communities shrank back and died, one by one. And yet they were here: And yet here was Ultimate, the latest link in a great chain that now passed back through a hundred million grandmothers, morphing and changing, loving and dying, back to Purga herself, and into the formlessness of the still deeper past beyond.

Ultimate and Cactus watched the tiny scramblings in the dirt. Then, hooting, the posthumans fell on the scrambling lizards. Most of them were too small to catch — you would close your hand around them only to see them squirming out the other side — and even when Ultimate managed to cram one into her mouth it was too small a morsel to be satisfying.

But they didn’t need to eat the lizards. They were playing. Even now you could have fun. But in the silence of New Pangaea their whoops and hooting cries echoed from the bare rocks, and as far as could be seen they were the only large creatures moving, anywhere.

The sunset came quickly.

The air was scrubbed clean of dust by the rains. As soon as the sun touched the horizon, darkness striped across the flattened land, small ridges, dunes, and pebbles casting shadows tens of meters long. The light in the sky faded from blue to purple, quickly sinking to black at the zenith. It was like a sunset on the airless Moon.

Ultimate and Cactus huddled together, the baby between their bodies. Every night of her life Ultimate had spent in the Tree’s enfolding vegetable embrace. Now the shadows were like raptor fingers reaching out for them.

But as the temperature fell, so Ultimate’s adaptations to the desert came into operation.

Her skin was actually hot to the touch. During the day her body stored heat, in layers of fat and tissue. In the cooler air of night, her body was able to radiate a lot of the heat back to the environment. If she had not been able to perform this trick of refrigeration she would have had to lose the heat by sweating — and that would have used up water she couldn’t afford to waste. And Cactus and Ultimate were breathing, deeply and slowly. That way a maximum amount of oxygen was extracted from each lungful of air, and a minimum amount of water was lost. Meanwhile Ultimate’s body was manufacturing water from the carbohydrates in the food she had eaten. She would finish the night with more water in her body’s stores than when she had started.

But still, for all this remarkable physiological engineering, the two of them could do little but sit and endure the night, breathing slowly, lapsing into a kind of dull half dream as their bodies’ functioning slowed to a crawl.

While above them a bewildering sky unfolded.

Ultimate had a grandstand perspective view of the Galaxy. The huge spiral arms were corridors of brightness that spanned the sky, studded with pinpricks of sapphire-blue young stars and ruby-red nebulae. At the center of the disk was the Galactic core, a bulge of yellow-orange stars like the yolk of a fried egg: the light had taken twenty-five thousand years to travel here to Earth from that crowded core.

In human times the sun had been embedded in the body of the huge flat disk, so that the Galaxy had been seen edge-on, its glory diminished by the obstructing dust clouds that littered the disk. But now the sun, following its slow orbit around the core, had sailed out of the Galaxy’s plane. Compared to the random scattering of a few thousand lamps that had marked man’s sky, this was like glimpsing the lights of a hidden city.

Ultimate cowered.

A bony hook rose in the sky. It was the Moon, of course, an old Moon, tonight a narrow crescent. The same patient face that had peered down on Earth since long before the birth of man was all but unchanged across half a billion years. And yet this thin crescent Moon shone more brightly over the new supercontinent than it had over the more equable lands in the past. For the Moon shone by reflected sunlight — and the sun had grown brighter.

Had she known where to look Ultimate might have made out a dim smudge in the sky away from the Galaxy’s disk, easily visible on the clearest nights. That remote smudge was the great galaxy known as Andromeda, twice the size of its neighbor. It was still a million light-years distant from Earth’s Galaxy — but in human times it had been twice as far away as that, and even then it had been visible to the naked eye.