By about 5,000 BC, therefore,30 humanity had learned to domesticate a wide diversity of edible plant species in a variety of climatic zones and landscapes, from the river floodplains of Mesopotamia to the high terrain of the Peruvian Andes and the tropics of Africa and New Guinea. By far the most significant plants we cultivated are the cereal crops. Grains like wheat, rice and maize, along with millet, barley, sorghum, oats and rye, have supported millennia of human civilisation. And the three most important systems of agriculture that have spread across most areas of the globe are wheat originating in the Fertile Crescent, rice in China, and maize in Mesoamerica.31 Today, these three cereals alone provide around half of all the human energy intake around the world.
Cereal crops are all species of grass. The astonishing truth is that we are no different from the cattle, sheep or goats that we leave out to pasture – humanity survives by eating grass.
Many grasses are hardy species of plant that can colonise land after pre-existing forest has died back with increasingly arid conditions, after fire has torn through an area, or in fact after any other disruption to the established ecosystem. Their survival strategy is to grow fast and put most of the energy they gather from the sun into their seeds, rather than building stout frames like trees – which is what lends them to cultivation. And this is the fundamental ecological reason that so many of us eat a slice of toast or a bowl of cereal for breakfast – wheat bread, cornflakes, rice crispies and porridge oats are all derived from fast-growing species of grass (and cereal crops of course also form the staple of other meals too).
But to make use of grassy cereal crops we are still faced with a biological problem. We don’t have four stomachs like a cow that would enable us to break down tough plant matter to release its nutrients. We therefore picked plant species that produce a concentrated dollop of energy in their grain – which, botanically speaking, is a fruit – and applied our brains to the problem rather than our stomachs. The millstone we use for grinding grain into flour (and the mechanisms we invented through history to drive its rotation, like the waterwheel or the windmill) is a technological extension of our molar teeth. And the oven we use for baking that flour into bread, or the pot we use for boiling rice and vegetables, are like external pre-digestive systems. We have applied the chemically transformative power of heat and fire to break down the complex plant compounds so that we can absorb the nutrients.
Origins of crop domestication.
POINT OF NO RETURN
The development of agriculture offered huge advantages to the societies that adopted it, despite the continuous labour involved in working the land and nurturing the crops. Settled peoples are capable of much faster population growth than hunter-gatherers. Children don’t have to be carried long distances and babies can be weaned off breast milk (and fed with milled grain) much earlier, which means that women can give birth more often. And in agricultural societies, more children are an advantage for they can help care for crops and livestock, mind their younger siblings and process food at home. Farmers beget more farmers very effectively.32
Even with primitive techniques, an area of fertile land can produce ten times more food for humans when under cultivation than when used for foraging or hunting.33 But agriculture is also a trap. Once a society has adopted cultivation and its numbers have grown, it’s impossible to revert to a simpler lifestyle: the larger population becomes entirely dependent on farming to produce enough food for everyone. There’s no turning back. And there are other consequences too. High-density, settled populations supported by farming soon develop highly stratified social structures, resulting in reduced equality and a greater disparity in wealth and freedom compared to hunter-gatherers.34
When farmers first moved down from the hills of modern-day Turkey into the plains of Mesopotamia in the sixth millennium BC, bringing with them their domesticated cereal crops, the Earth was entering the warmest, wettest phase of the Milankovitch cycles. The marshy ground of lower Mesopotamia was extremely fertile, its thick alluvial soil eroded out of the highlands to the north and deposited by the rivers as they flowed into the Persian Gulf. (Mesopotamia runs along a tectonic trough, as we saw in Chapter 1.) Productive agriculture fuelled a population boom, but by 3800 BC the climate was becoming cooler again and the rains less reliable: the fecund land between the rivers began to dry out. In response village farmers pooled their resources and manpower and congregated into larger and larger settlements from where they could operate more extensive irrigation systems.35 Building and maintaining these canals for both agriculture and transportation required, and in turn fostered, a centralised administration and increasingly complex systems of social organisation.36 So it was here in Mesopotamia that agriculture gave birth to the world’s first urbanised society. By 3000 BC more than a dozen large cities had been founded,37 their names still persisting in our cultural memory: Eridu, Uruk, Ur, Nippur, Kish, Nineveh, and later Babylon. The land between the rivers had become a land of cities, known to its inhabitants as Sumer.38 By 2000 BC, 90 per cent of the Sumerian population were living in cities.fn4
Mesopotamia lies in the tectonic trough formed alongside the Zagros mountains.
The emergence of civilisation in ancient Egypt is also believed to have been a product of climate change. During previous interglacials North Africa has been substantially wetter, dotted with large lakes and sporting extensive river systems, making the Sahara green with grasslands and woods.39 Roving tribes hunted across this landscape of savannah and woodland, and fished the lakes and rivers. The only signs remaining today of this thriving wildlife in the region are the rock paintings left by the hunters, depicting crocodiles, elephants, gazelles and ostriches.40
This climate optimum was not to last, though. As Mesopotamia began to dry, the monsoons also retreated from North Africa. The remaining pockets of surface water in the Sahara soon disappeared and the area desiccated rapidly by the end of the fourth millennium BC.41 Humans living here saw the environment around them degrading as it slipped into its current hyper-arid state. At first, they may have survived around the remaining oases, but as the region continued to desiccate they abandoned the dying land and retreated into the Nile Valley. Egypt had inherited the crops and animals domesticated in the Near East, with agricultural villages first emerging in the delta, and then along the Upper Nile, from about 4000 BC. Around 3150 BC, just as the Sahara finally dried out, the region was unified under the rule of the dynastic pharaohs.42 The process of increasing population density, social stratification and state control that marked the beginnings of Egyptian civilization was thus driven by climate refugees from the desertifying Sahara crowding into the narrow Nile valley.43
Ancient Egypt offers perhaps the clearest case of how the development of a civilisation is influenced by the combination of constraints and opportunities presented by its geographical setting and climate. A ribbon-like oasis running through the desert, the Nile’s reliable summer floods revitalise the plains either side of its course with mineral-rich sediment eroded out of its headlands in the highlands of Ethiopia. The mighty Nile also provided a simple means of transport. The prevailing north-east trade winds blow reliably in north African latitudes – we’ll return to them in Chapter 8 – which means that boats can sail south to Upper Egypt; and the Nile’s gentle current then allows an easy return downriver with the flow. This natural two-way transit system not only made possible the ready transport of grain, wood, stone and military forces, but the ease of communication along the whole length of Egypt helped consolidate the unified state.44
Egypt is well defended by natural barriers of inhospitable desert on either side of the Nile and so was able to resist invasion for most of its history.45 But this containment also prevented Egypt from extending its territory into a sprawling empire; apart from a late second millennium BC expansion along the Levant coast, Egypt remained a regional power along the Nile. While the river valley was fabulously productive for grain – it helped feed the city-states of ancient Greece an
d later became the breadbasket of the Roman Empire – it lacked an abundance of trees. Cedar timber was imported from the Levant, but it was too expensive to build a large navy to project Egyptian power across the Mediterranean or beyond the Red Sea.46
It was this combination of environmental advantages, simple internal transport, the ecological sustainability of agriculture offered by the Nile, and the natural defensive barrier of the enveloping desert that created the stable and long-lived Egyptian civilisation.47 Above all, it was the river that bestowed prosperity on the region. As the Greek historian Herodotus wrote in the fifth century BC, Egypt is ‘the gift of the Nile’.
So within a few centuries of the first Sumerian urban centres, cities and systems of greater social organisation were also emerging in the Nile, as well as the Indus and Yellow River valleys.48 Bountiful agriculture produced grain surpluses to feed these ever more populous settlements, and rulers coordinated the labour of growing workforces to construct impressive civic engineering projects like expansive irrigation systems, roads and canals, to further increase food production and its distribution. And within the cities, the proportion of the population released from the need to produce food could specialise in other skills: carpentry, metal-working, or even investigating the natural world. Stored surpluses of grain also supported large armies and generals soon consolidated the first empires of the world.
TAMING THE WILD
The birth of civilisation did not just depend on the cultivation of plant species. It also relied on turning wild animals into livestock.
The domestication of the first animal predates humanity’s settling down. Dogs were tamed from wolves by European hunter-gatherers during the last ice age more than 18,000 years ago,49 to help with the hunt or warn people of approaching predators. But the majority of the animals on our farms today were adopted into the care of humans much more recently, alongside the earliest cultivation of crops. Sheep and goats were domesticated in the Levant a little over 10,000 years ago – sheep in the foothills of the Taurus Mountains and goats in those of the Zagros mountain range.50 At around the same time cattle were domesticated from the wild aurochs in the Near East and India. The pig was domesticated in Asia and Europe between 10,000 and 9,000 years ago, and the chicken in South Asia around 8,000 years ago. In the Americas, the llama was domesticated in the Andes about 5,000 years ago, and the turkey in Mexico 3,000 years ago.51 The poultry species domesticated in the Sahel was the guinea fowl.52
In all these cases, domestication would have come at the end of a long process of cohabitation in the wild. People would not have invested time and energy into breeding, feeding, rearing and protecting animals, had they not already been intimately familiar with their habits and uses. So over a long road of humanity’s interaction with the animals around us, we turned from scavenging carcasses, to hunting and then to husbandry.
As we have seen, the transformation of wild plant species into cultivated crops allowed much greater food production, even if it came at the cost of a higher investment of time and effort. At the same time, the domestication of these animal species offered a reliable source of meat without the bother of a long hunt. But the domestication of animals also provided other opportunities that had not been available to roving hunter-gatherers. From an animal that has been killed you can extract its meat, blood, bones and hide. These are all extremely useful products for food, tools and shelter, but you only get them once. If, on the other hand, you care for the animals, rearing and protecting them, you can ensure a more reliable supply of these products as you cull your herd. And once livestock have been domesticated and are tended throughout their life, it is also possible to extract other useful products and services from the animals on a continuous basis, which you simply cannot exploit from wild beasts. Animal husbandry offers you completely new resources. This has been termed the ‘secondary products revolution’.53
Milk is one such new resource. First goats and sheep, then cattle, and in some cultures even horses and camels, were milked for human consumption – human mouths essentially replacing those of the animal’s own young. Milk provides a reliable source of nutrition – it is rich in fat and protein as well as calcium – and products made from it such as yoghurt, butter and cheese preserve these nutrients for long periods of time. Over its entire lifetime, a mare kept continually lactating supplies about four times more energy than what its meat at slaughter would provide.54 Only human populations native to Europe, Arabia, South Asia and western Africa are able to digest fresh milk, however.55 They have evolved so that the milk-digesting enzyme in their gut, which in other mammals only exists in babies, continues to be produced throughout their entire adult life. This is one of the clearest examples of humanity co-evolving with the animal species that we domesticated and selectively bred for our own purposes.
Wool, too, can be continually harvested from domesticated livestock. Wild sheep are hairy, with only a thin undercoat of short, fluffy fibres. Over generations of selective breeding humanity has emphasised this undercoat to provide the wool that was first plucked and then shorn for weaving into clothing, a development that occurred between 5,000 and 6,000 years ago.56 Llamas and alpacas served an equivalent function in South America.
And the domestication of large animals provided another important resource unavailable to hunter-gatherer societies: their muscle power as beasts of burden for transport and traction. The first species used to carry loads as pack animals was the donkey, but it was superseded by the horse, the mule (the infertile hybrid of horse and donkey) and the camel, all of which can carry larger loads further. Cattle were the first animals used for providing traction – pulling ploughs or wagons – as it is relatively easy to hitch a yoke to their horns; oxen (castrated bulls) in particular are strong but placid.57 The application of animal traction enabled the transition from agriculture powered by human muscle, with farmers using small hand tools like the hoe or the digging stick, to the use of ploughs. Livestock pulling ploughs gave another boost to food production. It also allowed marginal land, which had previously been considered too poor quality, to be turned to farming. Pack animals carrying goods over uneven ground or traction animals hauling carts and wagons over flat plains greatly increased both the bulk and the range of goods that could be transported, and so were hugely important for establishing long-distance overland trade routes. In addition, horse-drawn chariots revolutionised warfare in Eurasia in the second millennium BC; and later, once larger and stronger horses had been selectively bred and horseback riding became possible, cavalry became the most effective weapon of war.
Domesticated animals are especially beneficial when used in combination with each other. This was particularly important for nomadic, pastoralist societies: in regions with little arable land, people adopted a lifestyle supported almost entirely by large herds of livestock, with which they roamed between pastures. Animals such as sheep, goats and cattle are like food-processing machines. They thrive on the plains of grass, unsuitable for human consumption, and transform it into nutritious meat, marrow and milk. They also produce wool, felt and leather for clothing, bedding and tents. For pastoral societies these animals provide the very foundations of survival and a source of wealth that can be traded.58 Mounted herders riding swift horses are able to control huge flocks grazing over enormous areas of land, greatly amplifying the animal resources that pastoralists can maintain. And the bulk transport provided by oxen-hauled wagons, serving as mobile homes, enabled family groups to roam far and wide with their herds. It was this integration of herded livestock, horseback riding and animal traction that opened up the vast grasslands of central Eurasia as a habitat for pastoral nomads. The interaction – and often violent conflict – between these nomadic tribes living across the breadth of the steppes and the settled agrarian societies around its margins played a pivotal role in the course of Eurasian history, as we’ll see in Chapter 7.
The use of animal muscle power greatly expanded the capabilities of human societies – long-dista
nce trade and travel through different environments became possible with horse, mule and camel, and strong but slow animals like oxen or water buffalo provided traction for pulling wagons and ploughs. And with the innovation of the collar harness in fifth-century China, horses could be used for traction as well – a development that greatly increased medieval agricultural productivity in the heavy soils of northern Europe. Domestication of these animals to replace human muscles was the first stage in the progressive story of humanity’s marshalling greater and greater energy sources.59 Animal power reigned supreme for driving civilisation for around six millennia, before the introduction of fossil energy during the Industrial Revolution, when coal-fired steam engines began to propel trains and ships, and later the internal combustion engine, fed on liquid fuels refined from crude oil, enabled us to cover vast distances at astonishing speed.
Let’s now turn to the planetary forces that created these crucial animal and plant species we came to domesticate.
SEXUAL REVOLUTION
Our modern world of glittering skyscrapers and intercontinental flights still feeds itself on the grass species domesticated by our ancestors around 10,000 years ago. These cereal staples provide the majority of our daily energy needs, but of course humankind does not live on bread alone. Our diet also includes many other varieties of fruit and vegetable. Despite this apparent diversity, however, virtually all the plants we consume are members of one particular group, known as the angiosperms. I’ll explain their characteristics in a minute, but first let’s look at earlier forms of vegetation to put the astonishing evolutionary innovations of the angiosperms into perspective.
Origins Page 7