The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis (9 page)

If control of fire is uniquely human, and toolmaking occurs throughout the animal kingdom, then communication with symbols and words might fall somewhere in between. Many animals communicate with each other in some way. Humpback whales famously send sound waves through the water to attract mates. Honeybees waggle in a dance to tell other bees where to find nectar, and the African native vervet monkey screeches alarm calls to warn their fellow vervet monkeys of predators. But there is a big step between communication to signal approaching danger, to tell others where to find food, or to make offers for sex and the complex, often abstract ideas and emotions communicated through human language.

For culture to develop through cumulative learning, parents need a way to communicate with children to transmit ideas and
identify right from wrong. Language can compensate the costs of learning. Parents can communicate disapproval of harmful information, such as incorrect or flawed ideas drawn from trial-and-error experiments or picked up from peers. The Kelloggs would not have expected Gua, the
chimp, to become a well-behaved member of society, but they would have expected as much from their son, Donald. The ease with which children pick up language, with no particular teaching of grammatical rules and vocabulary, signals a significant survival benefit somewhere in our evolutionary past accruing to those who could
communicate via language. Our early ancestors may have initially developed a simple prototype language to communicate where to find food, or to alert offspring to danger. Then, as human brains got bigger and more adept at processing information, and human tongues acquired the ability to make many sounds, spoken language capable of combining a limited number of words into unlimited meanings became a part of the human toolkit.

Scrapes on bones or marks in the ground to count the days or the numbers of animals killed in a hunt may have expanded our early ancestors’ communication toolkits, as well. These symbols paved the way for more sophisticated systems. The Incas tied knots in color-coded cords, for example, to record which property belonged to whom. Ultimately, such innovations made bureaucracies possible, as they enabled societies to store information in a more permanent form instead of relying on
the powers of memory.

Except for
Homo sapiens
, all of the species in the human lineage eventually went extinct, but their early tools, their control of fire, and their use of language charted the course for their descendants. Why the other species in the human family flickered out—from what combination of changing climates, competition for resources, inability to adapt, and other calamities—is an intriguing and unanswered question. Regardless, the knowledge and culture we inherited from them gave our species a running start to expand across the world and twist nature to feed an expanding population. With that endowment, ours became the only human species to practice agriculture and harness the planet’s endowments on a grand scale.

Forager to Farmer

After many, many generations of early humans who foraged for seeds and fruits and hunted for meat, an unnamed person in an unknown place took a momentous step in our species’ short tenure on this planet. Somewhere in the Fertile Crescent, the arc of land that stretches across the valleys and hills around the Tigris, Euphrates, and Jordan rivers, a forager first collected the seeds of two grasses that would eventually give rise to wheat. These grasses, einkorn and emmer, still grow in northern Syria and southeastern Turkey.

On first glance these wild wheat relatives do not look like good candidates for cultivation. The seeds, the edible part of the plant, are small, and they disperse easily with the wind. These traits made it unlikely that anyone would have been able to collect the seeds en masse, but long-ago foragers must have spotted some grasses with seeds that stayed on the stem rather than blowing away. For humans, that was a valuable trait. They could harvest the seeds by hand and later with a sickle. By repeatedly collecting and then planting the seeds that did not blow away, the chances improved that the offspring would have seeds with this beneficial trait. People selected seeds with other desirable traits as well—large seeds, husks that come off easily with threshing, and seeds that ripen at the same time. Over thousands of years, einkorn and emmer
evolved into domesticated species. Humans, not the wind, controlled where and when the grass grew. Barley, chickpeas, lentils, peas, flax, figs, dates, and the less widely known vetch legume followed a similar process. Later, people bred sheep, goats, pigs, and cattle from wild species to produce more docile animals. Domesticated animals could eat food that people could readily supply. In return for the care and the food—and the protection against predators—that their human owners provided, the animals supplied meat, milk, and labor. People were at the helm of natural selection for these plants and animals. Our
ancestors transformed these species to be more and more at the service of humanity. And domesticated plants and animals, in turn, also transformed people, who went from being foragers to becoming farmers and herders.
Agriculture was born.

The story of wild species domesticated to suit human desires recurred independently in multiple places around the world beginning roughly 12,000 years ago. The seeds and skills spread outward from these centers as people migrated across the landscape. Updates on the pathways emerge as geneticists and archaeologists continue to unravel the past. As currently known, domestication first occurred in the Fertile Crescent and arose in China, South Asia, the Mediterranean, Ethiopia, Mesoamerica, the Andes, eastern North America, and perhaps New Guinea and the Amazon within a window between roughly 12,000
and 4,500 years ago. The pivotal progression, though spanning several thousand years, was little more than a flash of an instant compared with the 200,000-year span of our species’ existence on Earth or the millions of years that our cumulatively learning ancestors walked the planet.

Rice, the mainstay for billions of people today, got its start from wild grasses in the valley of China’s Yangtze River. Over time, people coaxed the genes of wild relatives of rice to produce plants with bigger edible seeds, fewer bristles, and seeds that did not fall off the stem before harvest. Many varieties of millet, soybeans, and peaches owe their existence to early Chinese foragers who
domesticated these crops from wild species.

Corn, the crop known as maize in many parts of the world, hails from the dry forests of southwestern Mexico. Corn’s wild grass relative, teosinte, is nothing like the corn we eat and feed to animals today. Teosinte is much smaller and has fewer kernels. The casings around the kernels are rock hard, and they inconveniently fall off the cob at different times. It might have taken several hundred to a thousand years for
the pioneering plant breeders to transform teosinte from its wild form to its fully cultivable domestic descendent.

Domestic species (right) and wild relatives (left) of corn, wheat, tomatoes, and rice clockwise from top left.

New World peoples domesticated squash, beans, and sunflowers in North America and Mesoamerica and
potatoes and cassava in South America. Sometime several thousands of years ago, probably in southern Mexico or northern Central America, a foraging ancestor must have noticed an exceptionally large specimen from a wild tomato plant clinging to a hill slope. They planted the seeds and perhaps saved the ones from the largest and fleshiest tomatoes to plant the next year. The process continued year after year. Over time, the cultivated tomato shared little likeness to its
coat-button-sized and bitter wild counterpart.

Each time human ingenuity succeeded in cajoling the genes of a wild species into cultivation, the roster of cultivated plants to feed humanity grew. But the roster did not grow very long. Only about 100 of the hundreds of thousands of wild plant species and 14 of the almost 150 species of large, terrestrial mammals came under humanity’s control.
These are essentially the same species that feed humanity today, with rice, corn, and
wheat dominating today’s diets.

What motivated hunter-gatherers to pivot toward becoming farmers and herders is a question that can only be answered with conjecture. Surely they could not have foreseen the multipronged repercussions of their decisions, how the act of guiding natural selection to meet human needs would change the course of human history and the planet. With farming, people could produce more food concentrated in one place. More people could be fed. And stored food meant more security against the vagaries of the weather. They started down the path toward settled life in towns and cities. Social stratification was set in motion. But so was the path toward diseases such as tuberculosis, measles, smallpox, and influenza. People crowded together were targets for pathogens to spread from cattle, pigs, dogs, and other domestic animals. Nutrition was worse after the switch from nuts, seeds, berries, and meat to a less-varied diet laden with newly domesticated starchy grains. The remains of skulls, bones, and teeth show that farmers had more tooth decay from a diet high in carbohydrates, a greater incidence of iron deficiency, and on average a
shorter stature than their hunting and gathering ancestors.

The transition from forager to farmer brought massive changes in lifestyle. Instead of moving across the landscape in more-or-less egalitarian groups in search of food, people remained in one place to sow the fields, thresh the grains, and stay near their stores of food. It’s difficult to say whether one way of life is better than the other. Certainly the pivotal switch had its drawbacks for health and nutrition.

Perhaps the changing climate prompted the shift from foraging to farming. The transition coincided with the retreat of the glaciers about 13,000 years ago and the beginning of the relatively warm, stable Holocene period. Large, complex brains, the argument goes, put humans in a prime position to develop agriculture and create complex cultures once the
swings in climate calmed down. It’s possible that dry
conditions and wild swings in climate from one decade to the next during the glacial Pleistocene simply made the evolution to farming untenable. Years that were unexpectedly too wet, too dry, too cold, or too hot would disrupt the slower process of domestication from forager to farmer. With the end of the glacial period and a more stable climate, perhaps the process could
move forward more smoothly. Or maybe the warming climate nudged plants to expand out from refuges where they had hidden during colder, drier times. People might have experimented with the spreading grasses.

Another conjecture as to why foragers became farmers speculates that the numbers of people grew too high in the places most endowed with plants for gathering and animals for hunting. Big game had become less abundant as technologies for hunting improved and the number of mouths to feed increased. Maybe food was in short supply. The population pressure could have edged some people from the best places for hunting and foraging into more marginal grounds. These refugees might have had no choice but to eat less favored foods such as cereals. Or perhaps the push toward domestication was fostered by some who saw prestige and social status in controlling stored food, a feat difficult to accomplish in hunting and gathering cultures. Conversely, people might have desired a sedentary way of life to bond communities and gain assurance that food would be available. The motivations were likely some combination of multiple factors, each playing out differently in the many centers of domestication that arose during
these pivotal times.

Regardless of the reasons, the transition to settled life changed the world forever. The number of people soared, with population growth rates jumping fivefold after farming became a way of life. In western Africa, for example, population growth increased sharply beginning about 4,600 years ago—the time that corresponds with the date of archaeological evidence for the origin of agriculture—and numbers continued to
swell for many centuries. Deaths increased from disease and
poor nutrition, but women had children more often. Soft foods made it possible to wean infants from breastfeeding at a younger age, so pregnancies occurred more often. More children may have been a bonus, as they meant more hands available to help in the fields and homes. And with settled life, women had no need to carry their young during their early childhood years, so it became possible to manage more children. With little motive to keep the number of children in check, and without prolonged breastfeeding, each family had more children,
and farming populations grew.

Farming cultures spread their knowledge, or simply pushed out hunter-gatherers, in places where climate and topography made agriculture tenable. Wheat, barley, and other crops domesticated in the Fertile Crescent spread rapidly east as far as Pakistan and west through Greece within a few thousand years, and then
traveled further into Europe. The stable climate of the Holocene continues to the current day with only a few bumps, such as the cold summers of the centuries-long Little Ice Age that hit Europe, Eurasia, and
North America in the fourteenth century. The relative constancy of climate has been the backdrop for all the twists of nature that followed the extraordinary ingenuity of the first farmers.