Evolution

Their feet, no longer required to grip branches at odd angles, became simplified into compact pads that lost much of their flexibility, and their big toes no longer worked as thumbs — but their new arched feet served as shock absorbers that enabled them to walk long distances without injury. Knee joints and thigh bones were redesigned to absorb the new upright load. The uprights’ spines became longer and curved to push their centers of gravity forward so it lay over their feet, and on the center line of their vertical bodies. New, specialized hip joints arose, a design that enabled them to lift one leg off the ground without losing their balance, as chimps would, so that they could walk without swaying. Their hands no longer had to combine manipulation with support and so became more flexible: their knuckles slimmed; their thumbs were freed up for more complex and delicate grasping. They became less strong, weight for weight, now that they didn’t need to haul themselves through the trees all the time.

Bipedalism helped the new savannah apes by allowing them to walk or run long distances between scattered sources of food and shelter, and by enabling them to reach fruit and berries at higher levels. As time went on they became more upright and taller, succumbing to the same pressures that had shaped giraffes. Bipedalism was such a major advantage, in fact, that it had already evolved independently in other ape lineages — although all of those creatures would succumb to extinction long before true humans appeared.

The graciles, the skinny pithecines who had hunted Far, were like upright chimps. They were more upright than Capo or any ape. But their heads were like those of apes, with protruding muzzles, small brain pans, and flattened nostrils. Their posture, even when standing upright, was bent, the head thrust forward, and their arms were long, their grasping hands reaching almost to their knees. When they walked, they had to use more steps than Far would have done to cover the same ground, and they could not move so fast. But over the short distances they usually covered they were efficient and effective movers.

They had stuck to the forest fringe. But they had learned to exploit the resources of the savannah: especially the carcasses of the great herbivores laid low by predators. When the opportunity presented itself, they would rush out of the cover of their forest to a carcass, clutching their simple flake tools, and slice through tendons and ligaments. Stolen limbs could quickly be brought back to the safety of the forest for butchery and consumption, and hammer-stones could be used to crack the remnant bones for marrow.

All of this forced a selection for smartness. Hominids lacked the teeth of hyenas or the beaks of the carrion birds; if they were to scavenge effectively they needed better tools than Capo’s rudimentary kit. Meanwhile their bodies had gotten better at processing meat. Many pithecine types had teeth capable of shredding uncooked flesh, and a more efficient digestive system able to tolerate such rich fodder.

Still they were marginal scavengers, at the bottom of the hierarchy of meat eaters; they had to wait their turn until the lions and hyenas and vultures had taken what they wanted from the larger kills. And scavenging, and even their rudimentary hunting, wasn’t the only pressure on the savannah apes.

The savannah was predator hell. The leopards and bears of the forests had been bad enough. Out on the savannah there were huge flesh-shearing hyenas, and saber-tooths, and dogs the size of wolves. Small, slow, and defenseless, the hominids, walking blinking out of their forests, were an easy target for such creatures. Soon some of the predators, like the dinofelis, even learned to specialize in taking hominids.

It was a ruthless attrition, a relentless pressure. But the hominids responded. They learned to understand the predators’ behavior, and how to seek effective refuge. They learned to cooperate better with one another, for there was safety in numbers, and they used tools to drive off their assailants. Even the development of language was driven, in part, by these pressures, as the specialized alarm cries that dated back to the forests of the notharctus slowly morphed into more flexible words.

The savannah shaped the hominids. But they were not hunters; they were the hunted.

The pithecines had their limitations. They needed the shelter of the forest as their base, for they were not built to withstand long periods out in the open. And they were tied to rivers, lakes, and marshes, for their bodies had little fatty tissue and so were not resilient to long periods without water.