Noth wrinkled his nose. This adapid used urine as its scent marker; every time it toured its range it would carefully urinate on its hands and feet to leave its signature. As a result, to Noth’s sensitive nose it stank badly.

Noth found a fallen beehive. He inspected it curiously, hesitantly. Hive bees were relatively new arrivals, part of an explosion of new forms of butterflies and beetles and other insects. The hive was abandoned, but there were whole handfuls of delicious honey to be had inside it.

But, before he attacked the honey, Noth listened carefully, sniffing the air. His sensitive nose told him that the others, high in the trees above, were still far away. He ought to be able to devour this food before they reached him. But he shouldn’t. There was a calculation to be made.

Noth was low-ranking among the males in his group. What Noth was expected to do was to call out, letting the rest know he had found food. Then the other males and the females would come, take as much honey as they wanted, and — if Noth was lucky — leave him a little for himself. If he stayed silent and was caught with the honey, he would be severely beaten, and any food left would be taken away, leaving him nothing at all. But on the other hand if he got away with it he might get to eat all the honey, and be spared any punishment…

The choice was made. Soon he was working the honey with his small hands, licking it down as fast as he could, eyes flicking around to check on the others. He had finished the honey and wiped away any traces on his muzzle by the time his mother reached the ground.

She still had her pup, Left, clinging to her belly. She began to scrabble at the floor, her fat-ladened tail held out behind her, silhouetted against the bright shafts of light that pierced the forest’s higher layers. She quickly uncovered more chunks of the fallen hive. Noth made a play of grabbing at the honey, but his mother pushed him away with a sharp shove and fell on it herself.

Noth’s father now tried to join in the bounty, but his mate turned her back on him. Here came two of Noth’s aunts, his mother’s sisters. They immediately rushed to their sister’s side and, with screeches, bared teeth, and handfuls of thrown leaves, drove Noth’s father away. One of them even grabbed a chunk of honeycomb from his hand. Noth’s father fought back, but, like most adult males, he was outsized by any one of the females, and his struggles were futile.

It was always the way. The females were the center of notharctus society. Powerful clans of sisters, mothers, aunts, and nieces, together for life, excluded the males. All this was a behavioral fossil: The dominance of females over males, and the tendency of male-female pairings to endure after mating, were more common in nocturnal species than those able to live in the light. This powerful matriarchy was making sure that the sisters had first call on the best of the food, before any male.

Noth took his own exclusion calmly. After all, the taste of illicit honey still lingered in his mouth. He loped away in search of more food.

Purga and Plesi had lived isolated lives, usually as females with pups, or as half of a mating pair. Solitary foraging was a better strategy for nocturnal creatures; not being part of a noisy group made it easier to hide from night hunters, who would wait in silent ambush for their prey.

But animals active by day did better to keep to groups, with more eyes and ears on the alert to spot attackers. The notharctus had even evolved alarm calls and scents to warn each other of different classes of predators — birds of prey, ground predators, snakes — each of which required a different defensive response. And if you were part of a group there was always the chance that the predator would take the next guy, not you. It was a cold-blooded lottery that paid off often enough to be worthwhile adapting for.

But there were disadvantages to group living: mainly, if there were large numbers of you, there was increased competition for food. As that competition resolved itself, the inevitable result was social complexity — and the size of the adapids’ brains had increased so that they were capable of handling that complexity. Then, of course, they were forced to become even more efficient at searching for food to fuel those big brains.

It was the way of the future. As primate societies became ever more complex, a kind of cognitive arms race would continue, increasing smartness fueled by increasing social complications.

But Noth wasn’t that smart. When he had found the honey, Noth had applied a simple behavioral rule: Call out if the big ones are close by. Don’t call if they aren’t. The rule gave Noth a good chance of getting away with maximum food and minimal beating. It didn’t always work, but often enough to be worth trying.

It looked as if he had lied about the honey. But Noth was incapable of telling genuine lies — planting a false belief in the minds of others — for he had no real understanding that others had beliefs at all, let alone that their beliefs could be different from his, or that his actions could shape those beliefs. The peekaboo game played with human infants — if you want to hide, just cover your eyes; if you can’t see them, they can’t see you — would have fooled him every time.

Noth was one of the most intelligent creatures on the planet. But his intelligence was specialized. He was a great deal smarter concerning problems about the others of his kind — where they were, their potential for threat or support, the hierarchies they formed — than about anything else in his environment. He couldn’t, for example, associate snake tracks with the possibility that he might stumble on a snake. And though his behavior looked complex and subtle, he obeyed rules as rigidly as if they had been programmed into a tribe of robots.

And still the notharctus spent much of their lives as solitary foragers, just as Purga had. It was visible in the way they moved: They were aware of each other, avoided each other, huddled for protection, but they did not move together. They were like natural loners forced to cooperate, uncomfortably imprisoned by necessity with others.

As Noth worked the forest floor, a troop of dark little creatures scurried by nervously. They had ratlike incisors, and a humble verminous look compared to Noth and his family, their black-and-white fur patchy and filthy. These little primates were plesiadapids: all but identical to Purga, even though she had died more than fourteen million years before. They were a relic of the past.

One plesi came too close, snuffling in its comparative blindness; Noth deigned to spit a seed at it; the seed hit the scuttling creature in the eye, and it flinched.

A lithe body, low-slung, slim, darted from the shade of the trees. Looking like a hyena, this was a mesonychid.

Noth and his family cleared off the ground quickly.

The plesi froze. But it was hopelessly exposed on this open forest floor.

The mesonychid hurled itself forward. The plesi squirmed and rolled, hissing. But the meso’s teeth had already taken a chunk out of its hind leg. Now more of the meso’s pack, scenting blood, came jostling toward the site of the attack.

The mesonychid was a kind of condylarth, a diverse group of animals related to the ancestors of hoofed animals. The meso was not an expert killer or a meat specialist but, like a bear or wolverine, it was an opportunistic feeder. All the condylarths were doomed to extinction ten million years before the age of mankind. But for now they were in their pomp, top predators of the world forest.

The other inhabitants of the forest floor reacted in their different ways. The lorislike adapid had a shield of thickened skin over bony bumps on its back, beneath which it now tucked its head. The big, dull barylambda concluded it was under no threat even from a pack of these small hunters; like the hyenas of later ages, the mesos were primarily scavengers and rarely attacked an animal much bigger than themselves. The taeniodont, however, decided that caution was called for; pompously it trotted away, its gaping mouth showing its high teeth.