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  But some adaptations would have been useful outside the original locality. A particular chunk of genome, which hails from wild barley growing in the Syrian Desert, has been found in a great variety of domestic strains, both in Europe and Asia. This stretch of DNA spread through domestic barley strains, and was preserved – it’s likely that it confers an important physiological advantage, such as drought resistance. The sharing of genes between separate populations of early domesticates is clearly evidence of some interbreeding. And it seems that these connections reflect more than just windblown and bird-borne seeds travelling around the region. The human communities of the Near East were well connected: similarities in material culture show that ideas were travelling around. But goods were being exchanged as well – there’s evidence of the sought-after volcanic glass, obsidian, passing from one community to another, in a way that we might be brave enough to call trade. It seems entirely reasonable to presume that both knowledge about cultivation and seed corn itself would have also been exchanged between different communities. But even with a ‘trade’ in seed corn, it’s also clear that the primary domesticates grown in various areas across the Near East during this dawn of the Neolithic were local, wild plants – not species brought in from elsewhere.

  In case this all seems like ancient history (which it is – and surely, interesting enough), there are implications of these insights into domestication and the genetic basis of particular traits that could be extremely important to us. If the precise effect of that stretch of Syrian-wild-barley DNA could be elucidated, for instance, then this knowledge could be used to improve crops in the future. We shouldn’t just view domestication purely as something that happened a long time ago, and which has no relevance to us now. Undoubtedly, there was an intensive period of biological change in crops between 10,000 and 8,000 years ago – including the evolution of large grains and a tough rachis. But domesticated species never stopped evolving – and we’re still influencing that evolution, perhaps more deliberately than ever before. Vavilov knew that studies into the deep past of cultivated crops would generate useful tools for modern agronomy. Nearly a hundred years later, that’s still the case, and the convergence of genetics and archaeobotany is highlighting all sorts of genes – and other areas of the genome – which might be usefully encouraged or even modified. Today’s efforts at improving cereals are just the latest steps along a road which started, even before humans began to sow and tend crops, with the gathering, threshing and milling of wild grains; with the baking of bread.

  This is all looking good, then. Genetics, archaeology and archaeobotany have harmonised. We have this coherent story of people seriously exploiting wild grains by 12,500 years ago, and probably even making flatbread from finely ground flour; the emergence of cultivation of cereals from around 11,000 years ago, and the gradual domestication of species, at multiple, connected centres. By 8,000 years ago, most of the wheat and barley being grown across the Near East is non-shattering and large-grained.

  There’s always more to learn. The current state of knowledge – as I write – certainly won’t be the last word on the domestication of wheat. The story is likely to change at least a little, as new evidence is discovered and analysed. But it seems at least unlikely that the whole mountain of evidence that has been gathered in at this point will be completely overturned. It feels as though we have the backbone of the story, and it’s unlikely to shatter. We know, well enough for now, the when, where and how of the story of wheat. But we haven’t yet cracked – at least in this telling of the story – the why.

  And this, perhaps, is the most interesting question of all. Because wheat is, at its heart, a grass. A humble grass. Surely not the most obvious foodstuff. Once you’ve got as far as grinding some grass seeds into a fine flour to make bread, as those ancient Natufians probably did with wild barley, then yes – I can see the attraction. But how do you get to that point? The small seeds of wild grasses seem so unappealing as food. There are surely plenty of other seeds, nuts and fruits which are more tempting: tasty morsels which don’t require anywhere near so much hard work to render them edible. What was happening, twelve and half thousand years ago, to make people look at something as humble and unattractive as grasses as a source of sustenance? What led our ancestors to depend on such an unlikely food? And why did it happen then?

  Of temperature and temples

  There’s a huge lag between the first evidence of wild wheat in archaeological sites – going back some 19,000 years ago – and the earliest evidence of morphologically distinct, domesticated wheats, some 8,000 years later.

  At the Syrian site of Abu Hureyra, domesticated cereals gradually replace wild grains between 11,000 and 10,500 years ago. The cultivated species include einkorn, emmer wheat and rye. It’s almost impossible to tell which of these species was domesticated first. Radiocarbon dating is extremely accurate, but it always provides a range rather than a specific year. Nevertheless, it’s been suggested that einkorn, with its simpler set of seven chromosome pairs, may have been the earliest species of wheat to have been domesticated – rather than being the later weed-turned-domesticate that Vavilov suggested it was.

  But why were all these grasses domesticated from the ninth millennium BCE onwards – not earlier, and not later? The timing of domestication suggests that external forces may have been important.

  After the peak of the last Ice Age, around 20,000 years ago, the world started to warm up. This was a bad thing for cold-adapted animals and plants, whose habitats were shrinking, but for temperate, warmth-loving species – including us humans – things were suddenly looking up. By 13,000 years ago, the ice sheets of the northern hemispheres had retreated, leaving behind fragments of ancient ice as glaciers, high up in mountain ranges, and covering Greenland and the north pole. The climate was becoming positively balmy. It wasn’t just the warmth and increased rainfall that plants were enjoying – there was an important change in the atmosphere as well. As the Ice Age drew to an end – between 15,000 and 12,000 years ago – the level of carbon dioxide in the atmosphere rose from 180 to 270 parts per million. Experiments have shown that this would have resulted in up to a 50 per cent increase in productivity for many types of plants, and that even resilient grasses would have seen a 15 per cent increase. The rise in carbon dioxide at the end of the Ice Age didn’t trigger the development of agriculture; there were so many other factors at play. But – and this is a big but – it may have been a necessary condition for agriculture to emerge – and perhaps explains why this development of human culture didn’t happen any earlier, in the Ice Age.

  As the world warmed and plant life flourished, grasses presented a dependable source of nutrition. As carbon dioxide levels rose in the atmosphere, the number of grains per plant would have increased, and stands of wild cereals would have grown in size and density – natural fields just waiting to be harvested. The choice of wild grasses as a food source starts to look less surprising – these were stable, dependable and plentiful resources. And, for a while, the earth was rich in its bounty.

  And then there was a hiccup. A fairly large hiccup – in the form of just over a millennium of winter. The downturn in global climatic conditions is known as the Younger Dryas. This rather obscuresounding name refers to a flower: the eight-petal mountain-avens or Dryas octopetala. This pretty, evergreen dwarf shrub with simple, white rose-like flowers loves the cold. If you have layered lake sediments, going back through thousands of years, and some layers contain lots of Dryas octopetala leaves, then you know that layer formed when the land around was alpine-tundra. Scandinavian lake-beds have deeper layers with mountain-avens leaves, dating to an older, shorter cold snap around 14,000 years ago – the Older Dryas. Then there’s a later, thicker layer, dating to 12,900 and 11,700 years ago – the Younger Dryas.

  In the Middle East, this global cold snap manifested itself in reduced rainfall – and cold enough winters for frost to form. Food resources must have been severely affected. So perhaps it was w
ith an air of desperation, in this period of relative drought and cold, that people tried to control their food supply – to grow the crops they had begun to depend on, rather than merely to gather them.

  While the cooling of the Younger Dryas might have pushed people towards cultivating crops, it’s possible that the warmth and bounty of the preceding millennia may have contributed to a change which made the deprivation of the cold snap even more acute. When the world had begun to warm up after the last glacial maximum, the human population began to boom. This is before agriculture emerges. It’s possible that the expanding human population may have somehow driven the change from hunting and gathering to farming – rather than the other way around. Perhaps the booming population was already placing resources under some pressure, just as the Younger Dryas loomed.

  The post-glacial baby boom wasn’t the only change amongst populations of Homo sapiens in the Near East – society itself was changing. The most striking evidence of this can be seen at a breathtaking archaeological site in southern Turkey, in Upper Mesopotamia – a site I was lucky enough to visit in 2008: Göbekli Tepe. I described it, back then, as ‘the most spectacular archaeological site I have ever seen’ – and it still is. I was given a tour by the director of excavations there, the German archaeologist Klaus Schmidt, who passed away in 2014, aged sixty. And so my memory of visiting Göbekli Tepe, with Klaus as my generous-hearted guide, is now tinged with sadness. He was so dedicated to this place – and the tale it had to tell – and keen to share its story with others.

  He made his discovery in 1994, while surveying the landscape for potential Palaeolithic sites. ‘I was suspicious when I first saw this site: no force of nature could make such a mound of earth in this location,’ Klaus told me. And he had been right to be suspicious: the mound was a ‘tell’, created by the accumulation of Stone Age ruins, rising some fifteen metres above the limestone plateau on which it sat. When Klaus started to investigate, he uncovered large, rectangular blocks of stone that couldn’t be moved. When he dug down deeper, he found that these blocks were just the tops of giant T-shaped standing stones, arranged in a circle. When I visited, Klaus had excavated four of these circles, but he believed there were many more, still buried in the rubble of the hill.

  I was blown away by the sight of these stone circles, as Klaus led me to the top of the hill and we looked down on one, in the trench below us. The standing stones were indeed huge, but they were also decorated. There were low-relief carvings – of foxes, boar, leopard-like creatures, birds, scorpions and spiders – on the sides of some of the stones. But there were also 3D sculptures, carved in one piece with the standing stones – one of a wolf, crouching on the short side of a pillar, and another of a ferocious, fanged animal head. Some stones were carved with more abstract forms, with geometric, repeating patterns. Klaus pondered the meaning of these carvings – could the animal forms represent different clans, or elements of a lost mythology? Or perhaps the guardians of the megalithic circles? He saw the images as prehieroglyphic communication – they clearly held meaning for the people who had made them, even if that meaning is now lost.

  Although Göbekli Tepe is unique, there are echoes of the architecture and images at other sites. Similar T-shaped pillars were discovered at the ancient settlement of Nevali Çori, and at three other sites nearby. Similar iconography – including depictions of snakes, scorpions and birds – is seen on shaft-straighteners from Jerf el Ahmar and Tell Qaramel, and on stone bowls from Çayönü, Nevali Çori and Jerf el Ahmar. Across this part of Mesopotamia, these people were clearly connected by shared, complex rituals and mythologies.

  A few stones were carved with huge, arm-like limbs that ended in clasped hands, with interdigitated fingers, on the front edge of the pillar. There were no other human features on these pillars, just the arms and hands. ‘Who are these beings made of stone?’ Klaus asked me, rhetorically. ‘They are the first deities depicted in history,’ he said – and he was probably right.

  Up on the hill at Göbekli Tepe, based on geophysical surveys which provide clues beyond the archaeologists’ trenches, there were probably twenty of these megalithic, monumental stone circles. But there were no signs of habitation, such as hearths, there. This seemed to have been a place where people gathered, to build monuments, to feast and worship – but it was not where those people lived.

  What makes Göbekli Tepe so gob-smackingly remarkable is its date. It was built 12,000 years ago. By hunter-gatherers, not farmers. And it’s certainly put the cat among the pigeons for theories about the development of human societies at the dawn of the Neolithic. The traditional story went something like this:

  An expanding human population requires more food;

  people adopt agriculture to fulfil this need;

  agriculture facilitates the accumulation of food surpluses;

  food surpluses are controlled by just a few powerful people – complex, stratified societies are born;

  these new power structures are underpinned by a new invention: organised religion.

  Göbekli Tepe is clearly a monumental problem for this sequence. In this corner of Upper Mesopotamia, at least, a complex society emerged in a hunter-gatherer context. Klaus believed that Göbekli Tepe provided unprecedented evidence of division of labour. ‘It’s very clear we must change our ideas,’ he told me. ‘Hunter-gatherers don’t usually work in the way we understand work.’ But things were clearly different at Göbekli Tepe. ‘They started to work in quarries. They started to have engineers to work out how to transport and erect the stones. There were specialists in stone-working, whose job was to produce sculptures and pillars from stone.’ For Klaus, Göbekli Tepe was concrete evidence of a society that had powerful, visionary leaders; that could assemble a workforce; and that could support artists. And it’s very hard to interpret the massive, decorated stone circles as anything other than a manifestation of organised religion. A fully fledged cult indeed – with powerful symbols, rich with myth and meaning for the temple builders. Before Göbekli Tepe, the idea that organised religion could have predated farming was just about unimaginable. On this hilltop, preconceptions and prejudices slid, crashing to the floor.

  Even Klaus found it hard to categorise Göbekli Tepe. It was pre-Neolithic – but it was clearly something different to even the last phase of the Palaeolithic. And even something distinct to the Epipalaeolithic. Klaus was tempted to call it ‘Mesolithic’ – yet it was unlike the Mesolithic of northern Europe, where the term applies to slightly more sedentary, but still nomadic, hunter-gatherers. Could it be classed as early Neolithic? The traditional idea of the Neolithic package – sedentary society, pottery, agriculture – is already fractured in the Near East, with the label of ‘Pre-Pottery Neolithic’ used for sites where sedentism and domestication of plants and animals is demonstrated, but pottery is still to come. What could we call Göbekli Tepe – ‘Pre-agriculture, Pre-Pottery Neolithic’? And if so, why ‘Neolithic’ at all? Faced with transitions and surprises like this, our normal categories – and any idea of packages of characteristics – break down, somewhat deliciously. History – and even prehistory – refuses to be pigeonholed as neatly as we’d perhaps like it to be.

  The creation of the monumental architecture at Göbekli Tepe must surely have involved a communal effort which extended beyond a few local settlements. And perhaps there’s a connection between that cooperation and another feature seen in the archaeological record at this time: evidence for feasting on a large scale. The settlement site of Hallan Çemi, occupied in the tenth century BCE, seems to be very much set up for partying, with dwellings arranged around a central courtyard littered with the remains of fires and animal bones. Göbekli Tepe itself is full of a huge amount of smashed-up animal bones – from gazelles and aurochs to wild ass. It looks as though people were congregating and feasting here again and again. Plant remains are few and far between at the site, but traces of wild einkorn, wheat and barley have been found. Perhaps the feasts involved gruel or bread
as well as meat. It’s even been suggested that the eventual domestication of cereals in this area could have grown from a culture which invested heavily, not in bread-making, but in beer-brewing – and that alcohol could have flowed freely, greasing the wheels of social intercourse, at these ancient feasts. Much later, the workers who built the Egyptian pyramids were paid in beer. Could there have been a similar reward for labouring at Göbekli Tepe?

  The importance of feasting in the Bronze Age and Iron Age – as a form of social glue, and a way in which elite individuals could demonstrate and enhance their high status – is widely accepted. But perhaps feasting has much more ancient roots – stretching right back to the dawn of the Neolithic. The improving climate after the end of the Ice Age may have provided the opportunity for individuals to accumulate wealth – in the form of surplus food – and influence – by providing lavish feasts. The scene was set for the emergence of stratified society. And so, Klaus Schmidt and his colleagues have argued, feasting – with or without beer – could have been the key stimulus for the development of agriculture.

  All of these factors are so inextricably intertwined, it’s impossible to pull out one and point to it as the single reason that people began to grow fields of wheat right across the Fertile Crescent, and beyond, around ten thousand years ago. It seems that agriculture probably wasn’t even a possibility until carbon dioxide levels in the atmosphere rose at the very tail-end of the Ice Age, and plants became more productive. And then expanding human populations may have placed resources under pressure, especially during the climatic downturn of the Younger Dryas. But there were clearly also changes within society as the human population expanded – which we now know preceded the adoption of agriculture. The dawn of the Neolithic in the Fertile Crescent seems to be intimately linked to the emergence of complex societies, of powerful people and powerful cults, and, perhaps, a predilection for feasting.