Evolution

Ignoring the pain in his chest Capo leapt to his feet with a roar. He couldn’t let Boulder get away with this. He scrambled up into the lower branches of a tree, drummed ferociously, hooted loudly enough to disturb birds that roosted high above him, and vaulted back to the ground. He let anger surge through him so that he bristled, and a proud pink-purple erection stuck out before him: a nice touch that, his trademark.

But Boulder kept his nerve. With the monkey limb wielded in his hand like a club, he began his own display, his stamping, leaping, and drumming just as impressive as Capo’s.

Capo knew he couldn’t afford to lose this one. If he did, given Boulder’s circle of blood-stained hunters, he might lose not just his status but his very life.

With an agility that belied his years, he leapt forward, knocked Boulder flat, and sat on his chest. Then he began to batter Boulder about the head and chest as hard as he could. Boulder fought back. But, save for youth, Capo had all the advantages: surprise, experience, and authority. Boulder couldn’t shift Capo’s weight, and he couldn’t bring his own powerful arms and legs fully into play.

Gradually, Capo saw, he was winning the battle in the minds of the rest of the troop, which was just as important as subduing Boulder. The young male’s followers seemed to have melted away into the trees, and the whoops of excitement and approval Capo heard now seemed to be directed at him.

But even as he battled to subdue Boulder, a slow deduction worked through Capo’s roomy mind.

He thought of the dying trees he had glimpsed beyond the fringe of the forest island, the speedy return of Boulder and his wanderers, their apparent hunger, their need to hunt.

Boulder had found nowhere to go. The forest patch was shrinking.

That had been true all of Capo’s life, and now it was becoming unavoidable. There was no longer enough room for them here. If he tried to keep the group here, the tension between them, as they competed for dwindling resources, would become too intense.

They would have to move.

At last Boulder gave in. He lay limp under Capo, cupped the older male’s buttocks, and even briefly stroked his still-erect penis, all gestures of submission. To drive home his point Capo kept battering at Boulder’s head for long minutes. Then he clambered off the prone younger male. Still bristling, he made his way into the forest, where he could afford to limp and massage the pain in his chest and nobody could see how he hurt.

Behind him the others fell on the vervet. Their stomachs could not digest flesh well, and later they would pick through their feces for lumps of meat to eat again. It was a digestive system that was going to have to improve, if the descendants of these rummaging creatures were to prosper on the savannah.

II

Since Roamer’s time, grass had remade the world.

The great epochal cooling of the Earth continued. As water was locked up in the Antarctic ice cap, sea levels diminished, and inland seas shrank or became landlocked. But with more continental landmass exposed, there was less sea to buffer the climate from extremes of heat and cold, and the weathering rock drew carbon dioxide from the air, making it less able to retain the sun’s heat. Cooler and drier: The planet had developed a vast feedback mechanism, driving its surface to still more arid, chilly conditions.

Meanwhile tectonic collisions created new mountain ranges: the Andes of South America, and the Himalayas of Asia. These new uplifts cast gigantic rain shadows across the continents; the Sahara Desert would soon be born in such a shadow. In the new desiccation, great belts of broad-leaved deciduous woodland spread from south and north toward the equator.

And the grasses spread.

Grass plants — huddling in their great crowds, able to rely on fertilization by windblown pollen — might have been designed for the new open, dry conditions. Grass was able to subsist on the sporadic rainfall that now fell, whereas most trees, with their roots delving ever deeper into the ground, found only dryness and could not compete. But the real secret of grass lay in its stems. The leaves of most plants grew from the tips of shoots, but not grass’s. Grass blades grew from underground stems. So grass could be cropped by a hungry animal, right down to the ground, without losing its power to regenerate.

These unspectacular properties had enabled grass to take over a world, and to feed it.