Tamed Page 7
Vavilov had studied in Britain, under the eminent biologist William Bateson. Through Bateson, Vavilov would have become familiar with Mendel’s ideas about inheritance. William Bateson had helped to revitalise and popularise the work of the Augustinian monk Gregor Mendel – including Mendel’s famous experiments with pea plants. Mendel had worked out that there must be some kind of ‘units of inheritance’, influencing whether his peas ended up green or yellow, smooth or wrinkled. He had no idea what those units were – we now know them as genes – but he predicted their existence. Mendel published his ‘Principles of Heredity’ in German, in 1866. More than forty years later, Bateson translated this seminal work into English, and it was he who came up with a name for the scientific study of inheritance, based on Mendel’s observations and theories: ‘genetics’.
Vavilov was also familiar with Darwin’s theory of evolution by natural selection. While in England, he spent plenty of time poring over the books and notes in the personal library of Darwin – kept at the University of Cambridge, where Darwin’s son, Francis, was Professor of Plant Physiology. Vavilov saw for himself how carefully and comprehensively Charles Darwin had studied the works of his predecessors, including the influential German botanist, Alphonse de Candolle, who had explored the origin of domesticated plants in two weighty volumes, published in 1855. Vavilov clearly enjoyed tracing the development of Darwin’s ideas in the notes scribbled in the margins, and at the end of these books. He admired Darwin’s thorough scholarship, his distillation of ideas, and his clear understanding of biological processes. ‘Never, before Darwin, had the idea of variation and the enormous role of selection been advanced with such clarity, definition and substantiation,’ he wrote.
Nikolai Vavilov believed that Darwin’s ideas were crucial to pinpointing where species – including domesticated ones – had first sprung into being. Darwin’s ideas about the geographic origin of species – articulated in On the Origin of Species – were essentially very simple. The origin of any species was likely to be the place which still possessed the greatest variation of types within that particular species. This is still a guiding principle in modern studies: the place with the greatest genetic – and phenotypic – diversity today is probably the place where that species has existed longest. It’s a useful guide, but runs into problems because, over time, plants and animals don’t stay put. But Vavilov believed that variation in closely related wild species could also be an important clue – so he spread his net a little wider, looking at wild relatives as well as the domesticated crops he was interested in.
Vavilov worked as a state botanist – his specific remit involved researching domesticated varieties of plants in order to inform Russian agronomy and plant-breeding. But he was equally intrigued by the historical and archaeological dimensions of his work. He believed that pinpointing the origins of domestic species would also be important to ‘explaining the historical destiny of peoples’. He also realised that, in elucidating the origin of domesticated wheat, there would be insights into a crucial moment in human history, when our ancestors moved on from simply gathering wild foods to growing them: when they made that transition from foragers to farmers. Vavilov knew that he was looking for history before history. The earliest domestication of species would have happened long before writing was invented. He wrote: ‘The history and origin of human civilisations and agriculture are, no doubt, much older than any ancient documentation in the form of objects, inscriptions and sculpture reveals to us.’
The pursuit of the origin of domesticated species had long been the preserve of archaeologists, historians and linguists – but Vavilov believed that botany and the new science of genetics could make an important contribution. In fact, he was quite disparaging about the nature of the traditional evidence. ‘Philologists, archaeologists and historians speak of “wheat”, “oats” and “barley”,’ he wrote in 1924. ‘The present state of botanical knowledge demands that the cultivated wheat species be distinguished into 13 species, oats into 6 species, all quite different.’
And he knew that his was no armchair science. He needed to get out there. He needed to understand landscapes and the plants that grew in them. And above all, he needed samples. ‘Every single packet of grain,’ he wrote, ‘every handful of seeds and every bundle of ripe spikelets is of the utmost scientific value.’
Vavilov came back from his Persian expedition with evidence of a huge variety of types of cultivated wheats. He divided wheat species into three groups, each with a different number of chromosomes. Species of soft wheat, including common or bread wheat (Triticum vulgare), had twenty-one pairs of chromosomes. Hard wheat, including emmer wheat (Triticum dicoccoides), possessed fourteen pairs, and einkorn (Triticum monococcum) had just seven pairs of chromosomes. Back in Russia, as few as six or seven varieties of soft wheat were grown. In Persia, Bokhara (in modern-day Uzbekistan) and Afghanistan, Vavilov recorded some sixty distinct varieties. He was clear that south-western Asia must be the homeland of this form of cultivated wheat. The distribution of hard wheats was a little different, with the most variation occurring in the eastern Mediterranean. Einkorn was different again – wild varieties of einkorn were found across Greece and Asia Minor, Syria, Palestine and Mesopotamia. He observed: ‘Most likely, the region of Asia Minor [Anatolia] and the areas adjacent to it appear to be the centre of einkorn variation.’
Vavilov believed that these separate centres of domestication for each type of wheat had influenced the characteristics of the various species in ways that were still relevant to him as an agronomist – as someone who was interested in improving crops. Hard wheats, like emmer, originated along Mediterranean coasts, where spring and autumn are wet, and summers dry. They needed moisture to germinate and start growing, but were quite drought-resistant when mature. Vavilov believed that emmer wheat was the earliest domesticated form of wheat – he wrote about it as ‘the bread wheat of ancient agricultural peoples’. And he had an intriguing theory about the later origin of einkorn.
When the earliest farmers began growing wheat, they found that certain other plants seemed to enjoy living alongside the sown crop. They had discovered weeds. And some of those weeds would eventually become domesticated themselves. Wild rye and oats were both common as weeds in fields of wheat and barley. Vavilov suggested that rye started to be grown as a crop by allowing the weed to replace the wheat over winter, or on poor soils or in harsh climates – where rye was hardier than the crop that had originally been sown. When Vavilov travelled around Persia, he saw fields of emmer wheat heavily infested with a weedy variety of oats. He suggested that farmers attempting to grow emmer wheat in more northerly latitudes would have found the oats taking over their fields. The farmers were effectively forced to adopt oats as a crop.
Vavilov provided many other examples of plants which he believed had started out as companion weeds, before becoming crops in their own right. Flax started as a weed amongst linseed crops. Garden rocket started as a weed in fields of flax. Vavilov noted that wild carrots commonly appeared as weeds in vineyards in Afghanistan, where, he wrote, ‘they practically invited themselves to be cultivated by the local agriculturalists.’ Similarly, cultivated vetches, peas and coriander probably originated from weeds in cereal crops. And Vavilov suggested that one of the grassy weeds infesting Anatolian fields of emmer would go on to become an important cereal itself – einkorn.
But back in Russia, Vavilov’s ideas were not popular. Darwin’s theories and Mendelian genetics were not in vogue in Stalin’s Soviet Union. Vavilov himself began to be seen as a threat; a dangerous weed. His student, Trofim Lysenko, whom Vavilov described as ‘an angry species’, stuck the knife in. Whilst on an expedition to the Ukraine, Vavilov was arrested, and incarcerated in Saratov Prison. He never left the prison, dying of starvation there, in 1943.
The Crescent and the sickle
Following Vavilov’s brave and pioneering work on the origin of crops, further botanical and archaeological evidence accumulated, to se
cure a grand sweep of the Middle East as the ‘cradle of agriculture’. Encompassing the land between and around the Rivers Euphrates and Tigris, and stretching across to the valley of the Jordan, this ‘Fertile Crescent’ has become renowned as the birthplace of the Eurasian Neolithic – one of the earliest places in the world where farming began. This is where the first domesticated wheat, barley, peas, lentils, bitter vetch, chickpeas and flax – all the plants which have become famous as the ‘founder crops’ of the Eurasian Neolithic – emerged. Recent studies have suggested that broad beans and figs should be added to this list.
Archaeology reveals the presence of very early farming communities, in what is now Turkey and northern Syria, between 11,600 and 10,500 years ago. But there’s evidence that people in the Middle East were exploiting wild cereals long before they domesticated these crops. Traces of domesticated cereals – including barley, emmer wheat and einkorn – are often found in shallower, more recent archaeological layers, directly above deeper and older layers containing the traces of their wild counterparts: the first wheat, barley, rye and oats to appear in archaeological contexts are gathered wild cereals.
Thousands of grains of wild barley and oat, dating to between 11,400 and 11,200 years ago, have been discovered at Gilgal in the Jordan Valley. Evidence of wild rye with some early signs of domestication – fatter grains with indications of having been threshed – has been unearthed at Abu Hureyra, on the Euphrates. And in some places, there is intriguing evidence of what the hunter-gatherers were doing with the wild cereals they were gathering.
At sites across the Southern Levant, the existence of small carved-out hollows in rocks has puzzled archaeologists for decades. Some have suggested that these cup-holes could represent the output from ancient masonry competitions. Or that they could symbolise genitalia. (Now, I totally accept that some cultural artefacts may indeed represent such important elements of anatomy – it would be weird if they didn’t. But it’s very hard not to see the interpretation of any old bump or hole as sexually suggestive as more indicative of the mind of the archaeologist than that of the ancient creator of such an artefact.) In any case, a more prosaic explanation for these particular hollows seems much more likely: that they are mortars used for food preparation – specifically, for grinding cereal grains into flour.
Many of these purported mortars have been discovered at Natufian sites – belonging to a culture which was well established by 12,500 years ago, a good 800 years before the earliest glimmers of the Neolithic in the area. The culture got its name from a cave in the Wadi an-Natuf, in the West Bank, excavated by Dorothy Garrod in the 1920s. The archaeological term for the period in which the Natufian occurs is the Late Epipalaeolithic. This means something like ‘peripheral Palaeolithic’ – it’s a term ripe with the implication and expectation of change. Society and culture was evolving, in a way which is clearly seen in the archaeology, but it’s not quite Neolithic yet.
The Natufian culture in the Southern Levant emerged around 14,500 years ago, and brought with it an important shift – from restless wandering to sedentism. The Natufians were still hunter-gatherers, but they were settled. They lived in permanent, year-round villages, rather than temporary camps. And by 12,500 years ago, then, these villagers were carving out stone cup-holes which look like mortars. The only cereal with large grains to grow in this area at this time was wild barley. And so one group of archaeologists recently decided to put these rock mortars to the test – how well would they work to grind barley grains into flour?
The experiment was as authentic as the archaeologists could make it. While they may not have been dressed up as ancient Natufians to carry out the test, they made sure that the whole procedure was performed using Natufian-style tools. First, they harvested wild barley with a stone sickle – previous experiments had shown that cutting stalks with reproduction flint sickles produced precisely the same polish seen on archaeological flint tools, interpreted as sickles. Then they gathered up the spikelets into a basket. Then they used a curved stick to thresh the barley, to separate the awns – the long bristles – from the spikelets. Then the spikelets were pounded in a conical mortar, with a wooden pestle, to remove the awn bases and the husks. The chaff was winnowed away by gentle blowing. Then the naked grains were returned to the mortar to grind them into flour, using the wooden pestle in stirring and pounding motions. The archaeologists finished off by using the flour to make a dough which they baked into an unleavened, flat bread, similar to pitta, over the coals of a wood fire. Then they ate their experimental loaf, and presumably, went for a beer.
The archaeologists had used an actual, ancient rock-cut mortar, at the site of Huzuq Musa, for their experiment. There were thirty-one narrow conical mortars at this site, as well as four large threshing floors close by. Based on their experiment, the archaeologists reasoned that the Natufians at Huzuq Musa could easily have processed enough barley for this to have been the staple food for the hundred or so inhabitants, 12,500 years ago. And it was important that the conical mortars seemed to work so well for de-husking the cereal grains. Barley with husks on could have been made into groats, porridge or coarse flour. But de-husked barley can be ground into much finer flour – and there really is only one reason for doing that: to make bread. It’s astonishing to think that the ancient inhabitants of Huzuq Musa could have been gathering barley, threshing it and grinding it into flour, and breaking bread with one another, at least a thousand years before anyone started to grow any cereal crops.
The idea that bread had already become a staple of Middle Eastern diets, hundreds of years before the inception of agriculture, makes the Neolithic Revolution easier to understand. In fact, once people had started to gather and process wild grains, I think domestication of those species – not only barley but wheat and other cereals – was almost inevitable. If you come to rely so much on one particular food, then perhaps depending on a harvest of wild grains becomes too risky. Better to grow some yourself. But this suggests our ancestors deliberately set out to cultivate wild plants. It’s likely that the beginning of agriculture owed much more to happenstance and serendipity than any carefully laid plans.
It seems that at least some of the changes that mark out domesticated cereals from their wild predecessors may have come about accidentally, or at least, as unintended consequences of human actions. A crucial difference between wild and domesticated cereals lies in the strength of the central spine, or rachis, to which the seeds are attached – forming the ear of wheat. In wild types, the rachis is brittle, and shatters: the individual spikelets that contain the seeds break away from the ear as they ripen, scattering themselves to the wind. An ear of domesticated cereal, on the other hand, remains intact after ripening. The rachis is tough – not at all brittle. This is a characteristic which would be severely disadvantageous to a wild grass – the seeds cannot be lost freely into the wind and scattered. In the wild, it would be a problematic mutation that would be swiftly weeded out by natural selection. But in a crop, the tough rachis becomes an advantage.
If harvesting was left until most ears had ripened, then any with a brittle rachis would already have lost many of their seeds – but the mutant, tough-rachis plants would still be hanging on to all their spikelets. So all of those still-clinging seeds would be carried to the threshing floor – some to be eaten, some to be sown again. And so the proportion of tough-rachis seeds and plants would increase with each generation. It’s another example of a certain characteristic almost selecting itself. Farmers did not need to be actively seeking out particular plants that were holding on to all their seeds. All they needed to do was to wait until most of the wheat was ripe, and then the wheat they harvested would be relatively enriched with the tough-rachis type – so the spread of this particular characteristic could well have been an unintended consequence of early farming practices.
In fact it’s possible that selection for a tough rachis started to operate even before farming began. Imagine being a hunter-gatherer, bringing b
ack armfuls of wild cereals to your settlement to process them. You’ll drop plenty of seeds on the way. But if any of the wheat you’ve gathered has a tough rachis mutation – those ears will stay intact. When you get back and start threshing, it’s inevitable some of those grains will escape, germinate and grow. Did the first fields spring up around the threshing floors, before any sort of cultivation was practised? It’s certainly a possibility but, ultimately, tough-rachis wheat would need to be sown. The characteristic may have developed as an unintended consequence of the way in which cereals were being harvested and processed, but once particular strains of wheat had evolved like this, they were trapped in their alliance with humans – the plants could no longer survive without our help. They could only grow on the edges of the threshing floor – or in fields where they were deliberately sown.
The tough-rachis feature spread through ancient wheat, slowly but surely, over some three thousand years, as people started to depend more and more on cereals, and to cultivate them. A few sites in the Levant have turned up a small proportion of non-shattering einkorn or emmer as early as 11,000 years ago. But by 9,000 years ago (7000 BCE), plenty of sites have 100 per cent non-shattering wheat: the trait has clearly become the norm – in the language of genetics, it has ‘become fixed’ – in populations of ancient domestic crops.
The transformation of wheat, from wild to domesticated, was a protracted process. That slow transformation was accompanied by a similarly slow change in the tools used by the hunter-gatherers-turned-farmers. Gradually, more and more sickles start to appear in archaeological sites. Unlike the more familiar, curved metal blades, the first sickles were made from flint or chert – this is still the Stone Age, after all. They are long blades which would have been fitted in wooden handles (archaeologists know, because just a few have been found like this, intact). The characteristic ‘sickle sheen’ along their edges shows that they were polished by repeatedly being used to cut the silica-rich stems of grasses. Sickles don’t appear out of the blue – they were probably tools that had been used for a long time for cutting reeds and sedges, before they were used for harvesting armfuls of wild cereals. From around 12,000 years ago, sickles become a little more frequent in the archaeological record – mostly in the Levant, the western limb of the Fertile Crescent. Archaeologists interpret this increasing use of sickles as indicating a new dependence on cereals – as it seems unlikely that the people of the Levant started to obsessively cut more reeds.