Evolution

Two huge chalicotheres worked their way slowly across the plain, plucking at shrubs with their huge paws. They picked only fresh shoots, and put them into their mouths, delicate as pandas. The taller, the male, was nearly three meters high at the shoulder. They had bulky bodies and stocky hind legs, but their forelegs were long and surprisingly graceful. But, because of their long claws, they could not put their front feet on the ground, and walked on their knuckles. In their bodies they looked a little like huge, short-haired gorillas, but they had long equine heads. These ancient animals were cousins of the horses. Once they had been widespread, but now the shrubs on which they depended were becoming scarce; this species was the last of the chalicothere kind.

Closer to hand, the apes could hear a steady, noisy rustling. Hesitant, they peered out. A family of a kind of elephant was working at the trees at the forest clump’s edge, using their trunks to pull away branches and cram foliage into their mouths. These were gomphotheres, massive creatures. Each had four tusks, a pair protruding from both upper and lower jaws, giving its face the look of a forklift.

This was the heyday of the proboscideans. The very successful elephantine body plan had spun off a whole range of species across the world. In North America the mastodons would survive until humans arrived. Another family was the shovel-tuskers like these gomphotheres, with their hugely expanded and flattened lower tusks. And, walking through Africa and southern Asia, there were the stegodons, with long, straight tusks. They were the ancestors of the true elephants and the mammoths, who had yet to appear.

The sound of the gomphotheres’ calls, carrying far in the cold morning air and echoing deep into the infrasonic, was eerie. These particular proboscideans were omnivorous. They were scarcely fleet-footed hunters. But on the whole a meat-eating elephant was best avoided.

That was when Frond, the spindly male, unexpectedly knuckle-walked out of the forest’s shade and into grass tall enough to come up to his shoulders. The grass waved around him, stirred by a breeze, languid waves crossing the empty acres.

Hesitantly Frond got to his hind legs. For a heartbeat he stood upright, peering out into a world beyond the primates’ reach, out into the green emptiness where animals walked, the antelopes, elephants, and chalicotheres grazing the abundant grass.

Then he dropped back to all fours and scuttled back into the forest’s shadows, his nerve gone.

Capo gave him a sound beating about the head for taking such a risk. Then he led his troop back into the deeper forest.

Capo hauled himself up an acacia tree, seeking fruit and flowers. Capo climbed steadily. He used a kind of shimmying style, pulling himself up with his arms while gripping the tree trunk with his feet to provide a platform.

It was a feat Roamer could not have achieved — or indeed any monkey. Capo’s apes had flat chests, short legs, and long arms. They had achieved greater flexibility by moving their shoulder blades to the backs of their bodies, which enabled Capo to reach up above his head. All this was equipment for hauling oneself up a tree trunk. Where Roamer had spent much of her life running along branches, Capo was a climber.

And this re-engineering for climbing had had another side effect, easily visible in Capo’s long, narrow body. Working vertically, with a new bone structure and system of balance, Capo was already preadapted to walking on two feet. Sometimes he did this in the trees, holding on to branches for balance, trying to reach the highest fruit — and sometimes his kind would stand up out in the open, as Frond had demonstrated.

As their bodies had been redesigned, the apes had become smarter.

In these tropical climes fruit trees rarely fruited simultaneously. Even when you found a fruiting tree, you might have a long way to travel to the next. So the apes needed to spend much of each day searching for patchy resources, foraging alone or in small groups, collecting together again to sleep in the treetop refuges. This basic architecture of food gathering had shaped their social lives. For one thing they needed to understand their environment very well if they were to find the food they needed.

And, given the way they lived their lives, their bonding was loose. They could split and recombine, forming special relationships with other members of the community, even though they might not see them for weeks at a time. Keeping track of a multileveled, fissile social complexity required increasing smartness. As the apes juggled their relationships, it was as if they were living through a soap opera — but it was a social maelstrom that honed their developing minds.