At last Gwerei had to show her. She bent over the dirt, clasping the tool, and stuck the blade deep into the ground. Then she began to walk backward, legs stiff, bent over, dragging the blade through the earth. She had made a furrow a hand’s length deep in the ground.

Juna saw that other people were doing just as Gwerei had, dragging their curved axes through the ground. She remembered seeing people do this yesterday. It was so simple a task a child could have done it, with enough strength. But it was hard work. After engraving furrows just a few paces long they were all grunting, their faces slick with sweat and dirt.

Still Juna had no idea why they were doing this. But she took the tool from Gwerei and rammed the blade into the ground. Then she bent as Gwerei had done and hauled the handle backward, until she had scraped a furrow just like Gwerei’s. One woman clapped ironically.

Juna handed the tool back to Gwerei. “I’ve done that,” she said in her own language. “Now what?”

The answer turned out to be simple. She had to do the same thing again, a little further on. And again after that. She, and the rest of the people here, had nothing to do but scrape these marks in the ground.

All day.

Where was the skill in this muck-scraping compared to even the simplest hunt, the setting of a rabbit snare? Did these people have no minds, no spirits? But perhaps this was part of the magic that the shamans here used to make their heaps of food, the abundance that allowed them to gather in great maggoty swarms and litter the ground with children. And besides, she reminded herself, she was a stranger here, and she must learn Gwerei’s ways, not the other way around.

So she bent to her dull, repetitive work. But before the sun had risen much higher, she longed to get away from this tedium, to be running on the high plain. And after a day of forcing her body — a machine exquisitely designed for walking, running, throwing — to endure this repetitive hard labor, the aches became so overwhelming that all she wanted was for it to stop.

The next day, she was taken to another field, and put to the same dull plowing. And the next day was the same.

And the day after that.

It was agriculture: primitive, but agriculture. This new way of living had never been planned. It just emerged, step by step.

As far back as Pebble’s time, even before true humans had emerged, people had been gathering the wild plants they favored and eliminating others that competed for resources. The domestication of animals had also begun accidentally. Dogs had learned to hunt with humans, and been rewarded for it. Goats had learned to follow human bands for the garbage they left behind — and the humans in turn learned to use the goats not just for their meat, but for their milk. For hundreds of thousands of years, there had been an unconscious selection of those plant and animal kinds most useful to humans. Now it had become conscious.

It had begun in a valley not far from here. For centuries the people there had enjoyed a steadily warming climate, and a rich diet of fruit, nuts, wild grains, and wild game. But then there had been a sudden drier, colder spell. The forests had shrunk back. The sources of wild food had begun to vanish.

So the people had focused their efforts on the grains they favored — the ones with big seeds that were easy to remove from the seed coats, and with nonshattering stalks that held all the seeds together — trying to ensure their growth at the expense of the less desirable plants around them.

Peas were another early success. The pods of wild peas would explode, scattering the peas on the ground to germinate. People preferred the occasional mutants whose pods failed to pop because they were easier to gather. In the wild such peas would fail to germinate, but they flourished under human attention. Similar nonpopping varieties of lentils, flax, and poppies were also favorites.

And so, by spreading the seeds of their preferred plants and eliminating those they did not favor, the people had begun to select. Very quickly the plants began to adapt. Within just a century, fatter-grained cereals, like rye, had begun to emerge. Some plants were favored for the large size of their seeds, like sunflowers, and others for the smallness of their seeds, like bananas, which became all fruit and no seed. Some genes that would once even have been lethal were now favored, like those for the nonpopping pea pods.

The first rye growers had not settled down immediately. For a time they had still collected their wild staples alongside their thin harvests. The new fields had served as dependable larders, a hedge against starvation in difficult times: As with all innovations, farming had grown out of the practices that had preceded it.

But the new cultivation had proved so effective that soon they devoted their lives to it. Most of what grew wild was inedible; nine-tenths of what a farmer could grow could be eaten. That was how these people were able to afford so many babies; that was what fed the great anthill heaping of the town.

It was the most profound revolution in hominid living since Homo erectus had left the forest and committed themselves to the savannah. Compared to this phase shift, the advances of the future — even genetic engineering — were details. There would never be so significant a change again, not until humans themselves disappeared from the planet.

But the farming revolution did not make Earth a paradise.

Farming meant work: endless, bone-cracking drudgery every day. As the ground was cleared of everything except what people wanted to grow, humans had to do all the work that nature had once done for them: aerating the soil, fighting pests, fertilizing, weeding. Farming meant the sacrifice of your whole life — your skills, the joy of running, the freedom to choose what you would do — to the toil of the fields.

It was not even that the food they so laboriously scraped from the ground was rich. While the old hunter-gatherers had enjoyed a varied diet with adequate amounts of minerals, proteins, and vitamins, the farmers took most of their sustenance from starchy crops: It was as if they had exchanged expensive, high-quality food for nutrition that was plentiful but poor in quality. As a result — and because of the relentless hard work — they had become significantly less healthy than their ancestors. They had worse teeth, and were plagued by anemia. Women’s elbows were wrecked by the constant work of grinding. Men suffered vastly increased social stress, resulting in frequent beatings and murders.

Compared to their tall, healthy ancestors, people were actually shrinking.

And then there were the deaths.

It was true that the mothers here did not have to sacrifice their babies. Indeed, the women were encouraged to have children as rapidly as possible, for children fulfilled the endless demand for more laborers for the fields: By the age of thirty, many of the women were exhausted by the endless drain of nursing and caring for weaned infants.

But where many were born, so did many more die. It did not take long for Juna to see it. Disease was rare among Juna’s folk, but it was not rare here, in this crowded, filthy place. You could almost see it spreading, as people sneezed and coughed, as they scratched weeping sores, as their diarrhea poisoned the water supply of their neighbors. And the myriad afflictions targeted the weakest, the oldest and youngest. Many, many children died, far more than among Juna’s folk.

And there was barely a handful of people her grandmother’s age. Juna wondered what happened to all the wisdom when the old died so cheaply and so early.

The days wore by, identical, meaningless. The work was routine. But then everything here was a routine, the same thing, day after day.