Evolution

Now the diplo matriarch came to a grove of ginkgoes, quite tall, ripe with green growth. She raised her head on its cable neck for a closer inspection. Then she dipped her head into the leaves and began to browse, tearing at the leaves with her stubby teeth. The other adults joined her. The animals began simply to barge down the trees, snapping trunks and even ripping roots out of the ground. Soon the grove was flattened; it would take decades for the ginkgoes to recover from this brief visit. Thus the diplos shaped the landscape. They left behind a great scribble of openness, a corridor of green savannah in a world otherwise dominated by forest, for the herd so ravaged the vegetation of any area that it had to keep moving, like a rampaging army.

These were not the mightiest herbivores — that honor went to the giant, tree-cropping brachiosaurs, who could grow as massive as seventy tons — but the brachiosaurs were solitary, or moved in small groups. The diplo herds, sometimes a hundred strong, had shaped the land as no animal had before or since.

This loose herd had been together — traveling forever east, its members changing, its structure continual — for ten thousand years. But there was room for such titanic journeys.

Jurassic Earth was dominated by a single immense continent: Pangaea, which meant "the land of all Earth." It was a mighty land. South America and Africa had docked to form a part of the mighty rock platform, and a titanic river drained the heart of the supercontinent — a river of which the Amazon and Congo were both mere tributaries.

As the continents had coalesced there had been a great pulse of death. The removal of barriers of mountain and ocean had forced species of plants and animals to mix. Now a uniformity of flora and fauna sprawled across all of Pangaea, from ocean to ocean, pole to pole — a uniformity sustained even though vast tectonic forces were already laboring to shatter the immense landmass. Only a handful of animal species had survived the great joining: insects, amphibians, reptiles — and protomammals, reptilian creatures with mammalian features, a lumpen, ugly, unfinished lot. But that handful of species would ultimately give rise to all the mammals — including humans — and to the great lineages of birds, crocodiles, and dinosaurs.

As if in response to the vast landscape in which they found themselves, the diplos had grown huge. Certainly their immensity was suitable for these times of unpredictable, mixed vegetation. With her long neck a diplo could work methodically across a wide area without even needing to move, taking whatever ground cover was available, even the lower branches of trees.

In the clever orniths, though, the diplos faced a new peril, a danger for which evolution had not prepared them. Nevertheless, after more than a century of life, the matriarch had absorbed a certain deep wisdom, and her eyes, deep red with age, betrayed an understanding of the nimble horrors that pursued her kind.

Now the patient orniths had their best opportunity.

The diplos still crowded around the wrecked ginkgo grove, their great bodies in a starburst formation. Their heads on their long necks dipped over the scattered foliage like cherry picker mechanical claws. Youngsters clustered close, but for now they were excluded by the giant adults.

Excluded, forgotten, exposed.

Stego ducked his head toward one of the diplo young. She was a little smaller than the rest — no larger than the largest African elephant, a genuine runt. She was having trouble forcing her way into the feeding pack, and she snapped and prowled at the edge of the formation with a massive birdlike twitchiness.

There was no real loyalty among the diplos. The herd was a thing of convenience, not a family grouping. Diplos laid their eggs at the edge of the forest, and then abandoned them. The surviving hatchlings would use the cover of the forest until they had grown sufficiently massive to take to the open land and seek a herd.

The herds made strategic sense: Diplos helped protect each other by their presence together. And any herd needed new blood for its own replenishment. But if a predator took one of the young, so be it. In the endless Pangaean forests, there was always another who would take her place. It was as if the herd accepted such losses as a toll to be paid for its continuing passage through the ancient groves.

Today it looked as if this runty female would pay that toll.

Listener and Stego took their whips of diplo leather from around their waists. Whips raised, spears ready, they crept through the rough scrub of saplings and ferns that crowded the edge of the forest. Even if the diplos spotted them they would probably not react; the diplos’ evolutionary programming contained no alarm signals for the approach of two such diminutive predators.

A silent conversation passed in subtle movements, nods, eye contacts.

That one, said Stego.

Yes. Weak. Young.