Picture this. It’s the 25th of December 1924. Christmas. A train is travelling swiftly through the wintry night near the rugged Soviet– Afghan border. A man named Nikolai Vavilov is on board. Having journeyed for months in this part of the world, at long last he is heading home. He is tired and full of ideas but right now, he is mostly hungry. He sets out for the dining car, but the space between his carriage and the next is cold, noisy and very dark, so he doesn’t realise that the connecting walkway is missing. And so, he falls. That Vavilov is not killed instantly is due to a grain of ludicrous, if painful, luck – he lands awkwardly on a steel buffer protruding from one of the carriages and manages to hold on. But now he is hanging precariously between the cars, his shouts drowned out by the roar of the engine.
Vavilov is a botanist, and what he had once thought would be a simple, quiet life of studying plants has turned out to be anything but. His current predicament isn’t even the half of it. His story is one for the ages, and it begins and ends with hunger.
Nikolai Ivanovich Vavilov was born in Moscow and would have been just four years old when one of the worst famines in Russian history began, in 1891. The problem started near the Volga River, which begins north of Moscow and curves eastwards and south like a 3700-kilometre-long question mark that ends in the Caspian Sea. Then, as now, much of the Volga River basin played a central role in Russian agriculture. In Vavilov’s time, this is where most of the nation’s food was grown. As ethnobotanist Gary Paul Nabhan describes in his book Where Our Food Comes from, the autumn of 1890 had been particularly dry, causing delays in planting. This alone would have been manageable had it not been quickly followed by an early, harsh winter that brought bitterly cold temperatures, but not the heavy snows needed to insulate spring seedlings. The resulting crop failures were widespread. More crops were planted that spring but these failed as well, and crop yields the following spring were also meagre due to weak seedlings and poor growing conditions. Then, as if things weren’t bad enough, there came five months of no rain and searing summer heat. Meanwhile, the Russian czar had allowed merchants to buy what little food was available and sell it at higher prices in Europe, while as many as 500,000 Russians starved to death.
Vavilov would have been too young to fully understand what was happening, but he would have known hunger and he would have seen it in others. He would have grown up knowing how those around him had suffered. He would have learned, in due course, how many of his extended family and neighbours had wasted away and died.
According to Nabhan, when Vavilov was older and the time came to choose a course of study, a series of dangerously low crop yields in the Volga region again raised the spectre of famine and served to clarify his sense of purpose. He chose to study agriculture, intent on finding a way to make crop diseases and poor yields a thing of the past. Around this time, an obscure idea published about half a century earlier was suddenly gaining traction. In the mid-19th century, a German monk named Gregor Mendel conducted a series of experiments with pea plants, through which he formed some rather interesting ideas regarding the inheritance of traits. It’s not as if family resemblances went unnoticed and, indeed, farmers were accustomed to selecting heritable traits when breeding crops and animals. But exactly how inheritance worked was anyone’s guess. Then along came Mendel with his pea plants and a theory that traits were passed down from parents to offspring via distinct ‘heritable factors’. Mendel’s work didn’t garner much attention during his lifetime, but by the early 20th century a number of biologists were beginning to take notice. One of them was William Bateson at Cambridge University, who proposed the establishment of a new field of biology dedicated to the science of inheritance. In a nod to the Greek word gennō, which means ‘to give birth’, he called it ‘genetics’. In due course, Mendel’s ‘heritable factors’ became known as ‘genes’.
So, there was Vavilov studying agriculture with a view to improving crop breeding just as this new science of genetics was gaining momentum. He was intrigued. In addition, interesting news reached Moscow. It seemed one of Bateson’s students at Cambridge, Rowland Biffen, had been puzzling over the problem of fungal diseases like wheat yellow rust. In a paper published in the Journal of Agricultural Science in 1905, Biffen noted how ‘some varieties [of wheat] inherit a constitution making them capable of withstanding the attacks of certain fungi’, while other varieties were highly susceptible. Working on a hunch, Biffen set up a series of crossbreeding experiments. Specifically, he took a variety of wheat that was resistant to yellow rust fungus and crossbred it with a variety that was notoriously susceptible. Around one-quarter of the offspring were resistant to yellow rust. This result was almost precisely what Biffen would have expected if rust resistance followed Mendel’s laws of inheritance. It meant yellow rust resistance could be intentionally selected during breeding.
This was huge. When Vavilov heard about this, he was so taken with the idea that he went to Cambridge to study genetics with Biffen and Bateson. There, he became convinced that if resistance to yellow rust results from a gene that can be passed from one generation to the next, and even crossed with other wheat varieties, then perhaps there were many other useful genes out there that conferred resistance to other diseases or maybe even tolerance to drought.
Of course, it was clear to Vavilov and others that genes did not simply appear out of thin air but were products of long arcs of evolution. Useful genes were probably out there somewhere – the question was where to find them. Fortunately, while at Cambridge, Vavilov spent a lot of time at the library. Not just any library, mind you, but Darwin’s personal library. It was here that an idea began to crystallise. When Darwin was honing his theory of evolution by natural selection, he had proposed that there must be a link between the evolution of a species and its original geographical surroundings. Vavilov knew that if he wanted to go hunting for genes, he needed to study up on phytogeography, which relates to the geographical distribution of plants, and of which one of the most fundamental principles is that species are not evenly distributed. In other words, certain species densely populate some parts of the world and cannot be found in others. It’s why we tend to find palm trees in the tropics and pine trees in the Arctic Circle, and why the global population of daisies is not arranged in a neat, grid-like pattern covering the entire land area on Earth. Plants grow only where they can, and only where their seeds have been dispersed in the first place.
Vavilov knew that if you were going to hunt for elusive genes, you needed to look for biodiversity hotspots to increase your chances. He had also learned that the longer a given plant species exists in a particular area, the more varieties of that species can be found, each providing clues to the original ancestor species. He reasoned that if he could find out where modern-day crop species had originated – where they’d first been selected from the wild and cultivated – then he might just find the genes he was looking for. The problem was, no one quite agreed on where crops had come from. It wasn’t for lack of trying: many had spent years looking through botanical specimens, archaeological evidence and historical records, and even studying linguistics, to try to pinpoint the origin of plant domestication. But nothing conclusive came of it. Then, one day, a troop of Russian soldiers stationed in Iran ate some bread and got very sick, and probably a little high. The Soviet government would eventually dispatch Vavilov to find out what had happened, and our understanding of the history of human agriculture would never be the same.
The outbreak of World War I had cut short Vavilov’s time at Cambridge. He had returned to Russia and, although unable to enlist due to a childhood eye injury, his expertise in botany made him uniquely useful to the war effort. The global conflict had ushered in an entirely new type of warfare, unprecedented both in its use of technology – automobiles, tanks, artillery and aircraft – and in the sheer number of people involved. It’s estimated that around seventy million soldiers were mobilised – and they all needed to eat. The ability to feed vast numbers of far-flung troops presented a huge logistical challenge for every military organisation involved in the war, one on which all other efforts hinged. However grand or clever your battle strategy, if your troops starved, you lost. Problems with food supply were taken very seriously.
Detailing the incident in his diary, Vavilov recounted that during Russia’s advance on Turkey, Russian troops had made incursions into north-eastern Iran and subsequently occupied a large amount of territory there. This included three northern provinces along the coast of the Caspian Sea. It wasn’t long before troops billeted in those provinces began experiencing a strange and frequent illness. It seemed something in the local bread was causing severe intoxication. To find out what was going on, the Department of Agriculture ordered Vavilov to go to Iran and investigate.
As it turns out, Vavilov was more than happy to comply because he had an additional motive: he had long wanted to collect samples of Persian wheat and here, finally, was his chance. But first he had a mystery to solve. Vavilov’s investigation revealed that the nearby wheatfields were heavily infested with a toxic darnel ryegrass, which was also contaminated with fusarium fungus. These had ended up in the bread flour, causing what he described as ‘bread drunkenness’. As it happens, darnel ryegrass is also particularly susceptible to contamination by ergot fungus, which produces a hallucinogenic alkaloid called lysergic acid – a very similar chemical to the drug LSD, so that may have been at play as well. The soldiers were ordered to stop eating local bread.
Job done, Vavilov turned his attention to the search for disease-resistant varieties of Persian wheat, and thus began his global hunt for the origin of agriculture. To say it was an adventure would be a gross understatement. Vavilov and his fellow travellers traversed glaciers and snowy mountain passes. They crossed oceans and deserts, travelled the Silk Road, and navigated narrow trails along dizzying cliff edges. That was the easy part. In the course of his endeavour, Vavilov was arrested and accused of being a spy, got malaria several times, as well as dysentery, and contracted typhus for good measure. He evaded bandits, was shot at, attacked by a mob, arrested again, and had stones thrown at him, and bricks, too. He nearly froze to death, twice.
Then, one cold Christmas night near the Afghan–Soviet border, Vavilov fell between two train carriages. He managed to save himself that night, clambering up onto the platform of one of the cars, having suffered only scrapes and bruises. But he was shaken by the fact that, after all he’d been through, he had nearly died on a short walk to dinner. He later conceded that the Afghanistan trip had been ‘rather difficult’ but was an important piece in the global puzzle of crop origins.
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As far as big changes in human history go, the Neolithic Revolution was a doozy. It refers to a transition that began around 12,000 years ago, during which many nomadic hunter-gatherer societies gradually adopted agriculture and began to live in year-round settlements, facilitating the rise of larger, more complex societies. This transition did not occur in all societies, nor did it occur simultaneously where it did. Instead, this revolution took place at different times in different locations all over the world. Nonetheless, by around 3000 years ago, most of the human population depended to varying extents on agriculture.
For many years it was assumed that the Neolithic Revolution had a single starting point, a solitary event that changed the shape of things, like a stone dropped in a still pond, its effects rippling ever outwards. The idea went that somewhere, a long time ago, one group of hunter-gatherers had gradually replaced all that gathering with plant cultivation. They had then shared this knowledge, and the new seeds, with the next settlement over, and then those people had shared the ideas and the seeds with the next group, and so on and so forth, until farming was all the rage, like some sort of Neolithic iPhone. The precise location of this original farming settlement – the centre of the agricultural ripple – was hotly debated. Initial suggestions focused on the earliest centres of civilisation, such as the Nile Valley in Egypt, or ancient Mesopotamia in what is now southern Iraq. This was not an unreasonable line of thought. After all, agriculture would have been a prerequisite for the establishment of the large, permanent settlements that later morphed into the first cities. But that all came much later. The story of the origin of agriculture turned out to be quite different to what most people had expected: there never was a single origin of crop domestication.
Through years of detailed analyses of crop and wild plant species, Nikolai Vavilov showed conclusively that human agriculture had multiple centres of origin, each developing independently through the cultivation and domestication of local plant species. At first, Vavilov believed there had been five of these centres: South-East Asia, South-West Asia, the Mediterranean coast, Central America and South America. By 1935, having conducted another decade of exploration and analysis, he was convinced there were at least eight. Since that time, the scientific community has amassed a wealth of archaeological and genetic evidence that tells us not only was Vavilov right about multiple origins, but there were even more than he’d realised. Michael Purugganan, who specialises in plant evolutionary genomics at New York University, tells me that, depending on whom you ask, the number currently ranges from as low as ten to around two dozen. Based on the research he has done in collaboration with archaeobotanist Dorian Fuller at University College London, his money is on the latter. He believes crop domestication arose independently in twenty-four places around the world, clarifying that these are places with a significant concentration of crop domestication, and this is ‘based just on the regions we looked at.’ In other words, more may yet be discovered.
The earliest evidence of crop domestication is found in a region Vavilov had loosely pinpointed as South-West Asia and which is now referred to as the Fertile Crescent, a swathe of land beginning near the Mediterranean in north-eastern Egypt and southern Israel and arcing upwards through Jordan, Syria and southern Turkey, across northern Iran, then down through Iraq to end at the Red Sea.
The story of agriculture, and its curious effect on seeds, goes something like this. Ever since Homo sapiens evolved around 200,000 to 300,000 years ago, we have survived by hunting and gathering, with a big emphasis on the gathering. Although there is no single ancestral human diet – it has varied widely across locations, climates and time – it is fair to say that hunting never guaranteed a meal. Instead, it is estimated that the bulk of our early ancestors’ calories derived from plant foraging. Plant foods of choice also would have varied across habitats and millennia, but evidence suggests they often included nuts, fruits, tubers and grasses. We know this from the unique marks left on fossilised teeth.
During the Last Glacial Maximum (LGM), which occurred approximately 26,000 to 19,000 years ago, a subtle shift occurred. It was a time in which the average global temperature dropped by around 4.3°C and massive ice sheets expanded over enormous parts of the northern hemisphere continents, while sea levels plunged to more than 120 metres below their current levels. For humans living in the regions most affected by the cold creep of those glaciers, life became particularly challenging, not least because of the significant change in available animals and food plants. It was a time of migration and adaptation. Some humans, it seems, began to do things a little differently than before.
In 1989 a drought struck Israel, causing the level of the Sea of Galilee to drop precipitously, revealing a 23,000-year-old Palaeolithic settlement now known as Ohalo II. There, scientists found the remains of several huts and hearths, as well as more than 100,000 seeds, including wild barley, wild oats and wild emmer. This is the earliest archaeological evidence of humans deliberately gathering these grasses. Further investigation suggested that ancient humans may have even tried their hand at cultivating this wild wheat, sowing and harvesting some nearby. It hints at a glimmer of knowledge, that at least as far back as the LGM, humans knew you could grow plants by deliberately planting seeds. Wheat and oats found on a grinding stone suggested that these Palaeolithic humans were processing the starchy grasses, maybe making bread or porridge, possibly even beer. There were also remnants of wild almonds, wild olives, wild pistachios and wild grapes. There were animal bones at the site, too, and the proximity to the lake’s edge implies access to fishing. It seems the people of Ohalo II would have eaten well for a time, and they might have been on the path to agriculture, but we’ll never know. Not so very long after its founding, the entire settlement burned down and was soon submerged by the rising water. Evidence of cultivation then vanishes from the archaeological record for thousands of years.
Starting around 12,000 years ago, and picking up speed in the ensuing millennia, the cultivation and then domestication of plants took place in various locations in the Fertile Crescent. It’s important to note that cultivation and domestication are not exactly the same thing. The cultivation of wild species – sowing seeds and harvesting plants – is the starting point, while the process of domestication involves selective pressures exerted by humans that ultimately cause crop species to accrue different traits and become distinct from their wild ancestors. Along the way, many of these new plant species become dependent on humans for survival. We first see this process play out in regards to wild emmer wheat in the southern Levant, an area that roughly corresponds to modern-day southern Lebanon, southern Syria, Jordan, Israel, Palestine and north-eastern Egypt. Domesticated cereals soon appear on the archaeological record in places like Abu Hureyra in northern Syria. Wild barley domestication also begins in the Jordan Valley and the areas surrounding the Zagros Mountains in Iran. The list then expands to include oats and flax, as well as pulses such as peas and lentils.
Clearly it wasn’t a case of one variety of domesticated wheat showing up in ancient Syria and then that same domesticated species of wheat showing up gradually across the Fertile Crescent. That would mean that the entire crescent represented only a single origin of crop domestication, and that’s not what happened at all. To use a stargazing analogy, sometimes what might seem at first like a single bright object to the naked eye can, with a powerful telescope, be revealed as a cluster of individual stars. In much the same way, the whole Fertile Crescent at first looked like a single bright centre of plant domestication, but further data, coupled with advances in archaeological and genomic analyses, have provided much better resolution, revealing numerous distinct centres of domestication throughout the region. Domestication was mostly a gradual process, with the journey from wild species to its tamed descendant taking a few thousand years on average. At a number of archaeological sites, domesticated cereals slowly replaced wild grains until eventually only the former could be found.
Like wheat and barley, rice also belongs to the grass family. The story of the most widespread species of domesticated rice, Oryza sativa, mirrors what happened in the Fertile Crescent. Evidence suggests that more than 10,000 years ago in China’s Yangtze Valley, people gathered wild rice, specifically a species called Oryza rufipogon, which grew prolifically in the wetlands of Asia and beyond, and still does. Those Neolithic hunter-gatherers brought this wild rice to their settlements where, as indicated by traces on grinding stones, the grains were processed into some kind of flour or meal. Beginning over 9000 years ago, in that same valley, people began to cultivate O. rufipogon. As biological anthropologist Alice Roberts details in her book Tamed, little by little, O. sativa, with short, starchy grains, began to appear alongside the wild species, eventually replacing its predecessor at numerous archaeological sites.
What happened next is still debated, but increasing evidence suggests that around 8000 years ago, people in India’s Ganges Valley began to harvest and possibly cultivate a local variety of wild rice, Oryza nivara, which was better adapted to warmer temperatures. We’ll never know whether this would have led to an independent domestication event because, thanks to the ancient trade routes, O. sativa arrived there around 4500 years ago. Whether deliberately or accidentally, O. sativa hybridised with the locally harvested version of O. nivara. Today, there many varieties of O. sativa rice, but they all fall into two main groups: japonica and indica. Japonica rice arose from that original domestication event in the Yangtze Valley and indica evolved from the hybridisation event in the Ganges Valley. Indica is now the most widely produced variety of rice in the world, with its grains tending to be longer than wider, and, true to its ancestral origins, it grows better in warmer climates. Basmati, jasmine and other ‘long-grain’ rices belong to the indica group. Japonica rices, however, are shorter, fatter and, because they are more glutinous, stickier. ‘Sushi’ rice is a japonica cultivar, as is arborio rice, which is often used to make risotto. Still, no matter what type of rice it is, every individual grain contains a seed.
Neolithic peoples in China also domesticated millet, soy and peaches. It seems that one of the earliest domesticated apples (Malus pumila) arose in Central Asia, too. In time, and again with the help of trade routes, this was hybridised with European crabapples (Malus sylvestris) to produce the ancestor of modern apples. Evidence suggests the first domesticated citruses also originated in southern China, but precisely where and when this and numerous subsequent citruses were domesticated is still the subject of much study. Suffice to say that there was a lot of crossbreeding along the way, and that if you were to draw the genetic links between a kumquat, a mandarin, a pomelo, a lemon, an orange, a grapefruit and a Mexican lime, you would produce something reminiscent of a Tokyo subway map. Meanwhile, a substantial amount of crop domestication took place in India and Southeast Asia, giving rise to a wide variety of unique cultivars of legumes and millets, not to mention mangoes.
It is important to note that Asia was not the only place where rice domestication occurred. Situated some 11,000 kilometres or so away from where O. sativa originated by the Yangtze, the Niger River carves an enormous crescent across the West African landscape. Beginning in the highlands of Guinea, it flows northwards into Mali, passing Bamako and Timbuktu, then meanders southwards into Niger and Nigeria. The range of the Niger River Basin, with its vast reach of tributaries and wetlands, extends across the modern boundaries of ten countries. Increasing evidence suggests that this region was once a cradle of agriculture thanks to the efforts of Neolithic West Africans. Recently, genetic studies have demonstrated that yams were first domesticated in the Niger River Basin, as was pearl millet. A little over 3000 years ago, people domesticated a local species of wild rice called Oryza barthii, which resulted in a new species, Oryza glaberrima, now known as African rice. It is still a staple crop in the region today, and it is the only species of rice besides O. sativa to have ever been domesticated.
But let’s return for a moment to the world of 9000 years ago, when the domestication of O. sativa rice was just beginning in the Yangtze Valley, and the domestication of wheats and barleys was underway in the Fertile Crescent. A similar phenomenon was taking place on the other side of the world, in what is now south-western Mexico, where another wild member of the grass family was gradually being coaxed into something that would in time profoundly change the diets of billions. Neolithic Mesoamericans in the Balsas Valley began to cultivate teosinte, a bushy plant that produced scrawny clusters of tough, nut-like seeds, subsequently domesticating it over thousands of years to produce what is now known as maize (Zea mays subsp. mays). Yet, even before maize had been fully domesticated in the Balsas Valley, early cultivars were being shared and traded throughout Central America and well into South America. The Balsas, in other words, set the domestication process going, and it not only continued locally but also independently in places as far-flung as the Amazon. The contemporary result is a wide variety of domesticated maize grown all over the Americas, reaching as far north as Canada. Alongside this veritable cornucopia, Neolithic Americans also cultivated and domesticated beans, squash, pumpkin, potatoes, sweet potatoes, chillies and tomatoes, among other species.
It’s important to underscore that plant domestication is not a simple linear event but something that arises from a complex interplay of local environmental conditions, larger scale climate effects, and population sizes and pressures, as well as culture. It also undeniably requires the local availability of plant species amenable to cultivation and then domestication. Then there is the ever-present matter of benefit versus cost. As Dorian Fuller and colleagues pointed out in the journal Trends in Ecology and Evolution in 2021, the shift towards plant domestication involves ‘initial costs of malnutrition, disease and labor traps that lock humans into dependency on agriculture’. In the context of food-sourcing traditions that were working well, the advantages of crop plant domestication would not have outweighed either the effort or the risk.
This brings us to the issue of Australia. There is a wealth of evidence that Australia’s First Peoples engaged in purposeful modification and management of the landscape – such as through traditional burning practices – to encourage the growth of certain plant species and discourage others, and foster the presence of animals in certain areas for hunting. There is also emerging evidence that Indigenous Australians engaged in plant cultivation in places, entailing the collection of seeds or tubers, then sowing and harvesting the plants. Precisely how long ago this began, how widespread it was, and whether any groups lived in year-round settlements practising intensive cultivation is the matter of continued study and debate.
Yet when it comes to plant domestication, Australia seems to be an outlier. None of the world’s current crop plants were domesticated in Australia. It could be that, for many and varied reasons such as those mentioned above, Indigenous Australians never domesticated any crop plants. However, Michael Purugganan cautions that just because such crops do not currently exist, it doesn’t mean this was always the case. ‘There are examples around the world where people domesticated something and then dropped it,’ he says. ‘So maybe they did manage to domesticate something, but then abandoned it for some reason.’ At this point, it can’t be ruled out. Moreover, it has been argued, quite fairly, that research on Aboriginal food production systems in Australia has historically received little attention and funding. As such, this area has been profoundly under-researched. As more research in this space is funded, especially collaborations involving Australia’s traditional owners, it will be interesting to see a more detailed picture come into view.
For now, this leaves us with at least two dozen distinct centres of origin of domesticated plant species, some arising in the same region, others separated by mountain ranges, continental expanses, vast seas or entire oceans. Yet, over and over, the domestication process changed seeds in astonishingly similar ways.
For one thing, seeds got bigger. As domestication played out, the endosperm – that package of nutrients meant for the plant embryo – often increased in size. There is an argument to be made that the first farmers would have preferred plants with larger grains and therefore selected for this trait. However, it looks as though early farmers were just favouring larger plants in general, and that larger seeds came with those larger plants. Either way, crop yields improved with such selections. In a 2017 study, plant ecologist Catherine Preece, plant biologist Colin Osborne and their colleagues at the University of Sheffield in the United Kingdom grew domesticated crops of barley, einkorn wheat, emmer wheat, oat, rye, chickpea, lentil and pea, alongside the wild progenitors of each species. They found that, compared to the wild relatives, the domesticated crops had 90 per cent greater seed mass and 40 per cent greater plant size, but 38 per cent less chaff or pod material. The overall result was a 50 per cent higher yield. Seed size increases have also been documented in domesticated mung-bean, soybean and horsegram legumes. In another 2017 study, Colin Osborne and colleagues showed that domesticated varieties of seven vegetable crops, including beets, carrots and potatoes, produce seeds that are 20–250 per cent larger than their closest wild relatives. Yes, potato plants do indeed produce seeds, although they are rarely used in propagation. This makes the study’s findings even more interesting because although domesticated potatoes largely have been propagated for millennia by tubers or cuttings, the seeds got bigger anyway.
Probably the most profound change, and something now considered to be a key hallmark of plant domestication, was the loss of seed dispersal. That’s a pretty big deal, because it represents the rapid loss of a hard-won survival mechanism in plants. To recap: plants spent millions and millions of years evolving increasingly sophisticated ways of physically moving their populations across the landscape, finally arriving at a wildly successful solution in the form of seeds, whose key party trick is that they can be released from the parent plant and travel – via wind, water or animal – anywhere from a few centimetres to thousands of kilometres. This natural seed dispersal was so successful that it ultimately enabled plants to inhabit most of the dry land on the planet. Then, beginning just 12,000 years ago, Neolithic humans come along and start cultivating a few plants, and pretty soon seed dispersal is one of the first traits to get chucked in the proverbial bin. This didn’t just happen once but time and time again.
The ancestors of cereal and legume crops possessed a trait called ‘shattering’, which is still observed in many wild relatives of crops today. It works like this: when the plant reaches maturity and the seeds are ripe, the seed heads release the seeds, or in the case of seed pods they break open. In cereals, the grains – which are really just seeds encased in a thin husk – are enclosed in spikelets attached to a central stem called a rachis. When wild cereals reach maturity, this rachis becomes fragile and breaks, releasing the seed-carrying spike-lets to go where they may. But in domesticated cereals, the rachis is tough and does not release the spikelets. In domesticated legumes, seed pods no longer break open with enough force to disperse the seeds inside, or they might not even open at all. The archaeological record reveals that numerous crops, particularly those grown in arid climates, gradually became ‘non-shattering’ over the course of a few thousand years. To use the examples of wheat and barley, people in the Fertile Crescent began cultivating wild cereals around 12,000 years ago, but by 8000 years ago these wild cereals had been largely replaced by non-shattering cereals. Rye and oats followed suit to become non-shattering crops by around 4000 years ago. The same thing happened with rice and maize crops.
Michael Purugganan says it’s likely that early farmers were not consciously selecting the non-shattering trait. Instead, it was probably a beneficial by-product of the tools they were using. ‘The loss of seed dispersal, the shattering trait that drops off, it seems to have appeared in coincidence with the rise of the use of sickles or harvest knives,’ he tells me. ‘You can imagine that if you were a farmer and you cut the stem and if the seed fell off, you wouldn’t gather the seed. So, unconsciously, when you were using sickles, those seeds that managed to stay on the stem were the ones you used to propagate the next generation.’ Yet, in West Africa, rice was often harvested by swinging a deep basket through the tops of the plants. This practice, which continues in many places today, favoured plants that retained the shattering trait. It was a slight weighting of the evolutionary die that, when cast again and again over a few thousand years, led to the gradual loss of seed dispersal. Many fruit crops, it should be noted, lost seed dispersal too, albeit in a different way. Because the megafauna of the Pleistocene had largely vanished by the Neolithic, many fruit trees lost their primary animal dispersers. Moreover, the more controlled setting of agriculture – namely, farmers armed with pointy weaponry – would have discouraged dispersers that had not gone extinct.
Domestication also hampered seeds’ ability to disperse forwards through time, says Purugganan. Loss of seed dormancy is another distinguishing feature of domesticated crop plants, one that recurred in a wide variety of crops all around the world. Dormancy is simply the blocking of germination, and the domestication process somehow weakened this block, allowing germination to occur faster and under less stringent conditions. It seems that gradual, microscopic changes in seed structure played a big part in what happened.
In 2017, archaeobotanists Dorian Fuller and Charlene Murphy at University College London published the results of an interesting experiment. Horsegram is a legume that was domesticated in India during the late Neolithic. To understand precisely how horsegram seeds changed during domestication, the researchers analysed twelve horsegram seeds recovered from archaeological sites in southern India, spanning a date range from 2000 BCE to 500 CE. For this, they got a little help from something a lot more modern, namely a synchrotron, which is a football field–sized particle accelerator that flings electrons around a central ring at almost the speed of light. The laws of physics being what they are, speeding electrons would much prefer to follow a straight path, but a series of powerful magnets force them to follow the path of a circle. In order to take the curve, the electrons release energy in the form of X-rays which are captured and funnelled towards an experimental station. There, each of the ancient seeds was positioned and rotated, while thousands of microsecond-length exposures were recorded. This procedure, called X-ray tomography, produces high-resolution 3D images of very, very small things. Fuller and Murphy were able to show that over the course of 2500 years of domestication, the seed coats gradually became thinner. We’re talking an average loss of around 1 or 2 micrometres of thickness every thousand years. That’s all it took to weaken the seed coat, making it more prone to be affected by environmental conditions, especially the presence of water.
The loss of dormancy was likely an unconscious selection, too, says Purugganan, explaining that it ‘occurred when humans essentially developed this new environment called the farm’. For crop seeds, this more controlled environment meant that tough seed coats were no longer essential to species survival, and for seeds that had previously relied on animal ingestion for dispersal and germination, a tough coat was no longer required to endure the abuses of the digestive tract. Farmers were also favouring varieties that sprouted regularly each year over varieties that lay dormant for long periods of time. Reduced seed dormancy led to more frequent and predictable harvests.
‘I think domestication is a really cool process,’ Purugganan tells me. ‘Humans took plants from the wild, and by just nurturing them and bringing them into their gardens and farms and orchards, [they] really changed the evolution of these species to become the crops that we now use for our survival.’ For plants, though, domestication was – and still is – a risky co-dependency. After millennia of cultivation, many crop species now had weaker seeds and were almost entirely reliant on humans for seed dispersal.
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Nikolai Vavilov was one of the first people to appreciate just how truly diverse are the world’s crop species, and how precarious that diversity is. Be it from a crop plant or a wild relative, Vavilov knew each seed was a valuable genetic resource uniquely shaped by the weft and warp of shifting climates, ecosystems, pathogens and, for domesticated species, human cultivation. There were genes to be discovered in these seeds. There were genes for heat tolerance and drought tolerance, genes that allowed a plant to thrive at high altitudes or low, to endure in cool weather or survive excessive rain. There were genes of resistance, to rusts and rots, to spots and blights, each like a thread of gold that could be found if you knew just where to look, yet far more valuable because you cannot eat gold and you certainly can’t grow it.
Vavilov began one of his earliest plant collections while working in England. He took it with him on the way home at the outbreak of World War I, but the merchant steamer on which he was travelling accidentally struck a British mine. Vavilov survived, but his collection did not. Undaunted, he began again. He kept learning languages, too, and was rumoured to have been fluent in at least fifteen, so he could learn the minutest idiosyncrasies of the plants he encountered, and ask, wherever he went, if he could have a few seeds. With the help and generosity of farmers and villagers across five continents, he collected and catalogued seeds of maize in Mexico, barley in Ethiopia, sunflowers from the Hopi mesas of Arizona, wild onions in Tajikistan, wild olives in Lebanon, native wheat in Syria, radishes in Japan, quinoa in Peru, wild quinine in the Andes, hemp seeds and peas in Morocco, soyabeans in Korea, seeds of millet in China and rye in India. He collected rice seeds all over Asia and grains of wild wheat wherever he could find it. His expeditions often resulted in the collection of thousands of samples, all of which were sent back to Russia to be meticulously catalogued and stored. On the night Vavilov fell between the train cars, he was transporting home a huge collection of wheat varieties unique to Afghanistan.
Vavilov was not the first to save seeds, of course. That had been standard practice since plant cultivation first began. But he was the first to do it on such a grand scale. By the late 1930s, he had overseen the establishment of the first global plant genebank in Leningrad, comprising around 200,000 seeds from all over the world. As the collection was growing, two more major famines swept through the region. The first of these devastated Russia in 1921. This was followed by an even larger scale famine in the Soviet Union in 1932. Millions starved, then millions more. Vavilov and his colleagues at the genebank understood all too well the grave threat that food insecurity presented. They knew, too, just how valuable this new resource was and how genetic studies of all those different species might just reveal the precious genes the world’s farmers needed. They were willing to give their lives to defend this idea. And in the end, many of them did.
Trouble first arrived in the form of a man named Trofim Lysenko and his baffling – and ultimately dangerous – ideas about seed germination. Lysenko had risen to prominence on the back of reports that he had found a new way to boost annual crop yields by not only planting winter crops in autumn to be harvested in spring, but also planting winter crops again in spring to generate a second harvest. Seedlings of winter wheat need several weeks of winter temperatures to thrive and reproduce, so this second crop season should have been impossible, but Lysenko claimed that just soaking the seeds in some cold water or packing germinating seedlings in snow for a few days was enough to fool the plants into growing well and producing a bountiful harvest. Moreover, he claimed that subsequent generations would also produce high yields. And so, with the USSR facing food shortages, along comes this plucky upstart from a peasant background to quickly solve the nation’s biggest problem. He seemed the very embodiment of Soviet grit and resourcefulness and was welcomed by government officials and agronomists alike.
At first, Vavilov was intrigued and he agreed to mentor Lysenko, but it wasn’t long before Vavilov began to smell a rat. When he tried to reproduce Lysenko’s findings, nothing worked. As Vavilov began to publicly criticise Lysenko’s work, Lysenko fired back. He became an outspoken critic of genetics, calling it, among other things, ‘an anti-people field of science’, and dismissing the idea that ‘a substance of heredity’ could possibly exist. In his view, DNA and genes were pure fantasy.
‘The emerging ideology of Lysenkoism was effectively a jumble of pseudoscience, based predominantly on his rejection of Mendelian genetics and everything else that underpinned Vavilov’s science,’ wrote University of Queensland plant scientists Ian Godwin and Yuri Trusov in The Conversation. Instead, Lysenko believed that crop plants could acquire new fundamental traits in their lifetimes if merely exposed to the right environment, and that these new traits could then be passed down to subsequent generations. It was an idea that meshed well with the prevailing Soviet ideology: just replace ‘crop plants’ with ‘citizens’ and you get the idea. That complex plant traits could be coaxed into existence within the confines of a single generation was, of course, bunk. ‘None of this could be backed up by solid evidence,’ say Godwin and Trusov. ‘His experiments were not repeatable, nor could his theories claim overwhelming consensus among other scientists. But Lysenko had the ear of the one man who counted most in the USSR: Joseph Stalin.’
As Lysenko’s duplicitous star rose, Vavilov fell from favour. The entire science of genetics, along with anyone who subscribed to it, was twisted by Lysenko and his supporters into something to be seen as bourgeois, capitalist and therefore anti-Soviet. Vavilov was in turns dismayed and furious, and he did not go quietly. But although Vavilov continued to speak out against Lysenko and his policies, Lysenko’s influence at the highest levels of government only grew. His disastrous ideas directly contributed to the large-scale impairment of Soviet agriculture. People who had been forced onto collective farms by the thousands were now required to use Lysenko’s useless farming techniques. It took only the slightest environmental nudge for everything to fall apart. Crops failed and the ensuing famine in 1932 led to the deaths of millions. Yet Stalin, and by extension Lysenko, remained in power, while Vavilov and his colleagues in plant genetics were vilified.
By 1940, a new war in Western Europe was gaining momentum. These were the early days of what would become known as World War II, but the Soviets weren’t in the fray just yet. For a few years the Molotov–Ribbentrop Pact remained in force, a tenuous agreement of non-aggression between the USSR and Nazi Germany. While Anglo–Soviet relations had never been rosy, this had the effect of turning Britain and the USSR into formal adversaries – sort of enemies-in-law, if you will. Lysenko, scenting blood, seized the opportunity to finally rid himself of his rival. In an impassioned speech at the Kremlin, he was quick to frame genetics was a Western ‘bourgeois’ science, and that those who studied it were ‘saboteurs’. It’s said that Stalin himself stood and applauded. In that bewildering moment, genetics became the domain of traitors. On 6 August 1940, Nikolai Ivanovich Vavilov was arrested on the false charges of spying and sabotage and was sent to prison to await execution by firing squad. One could only hope, as a small mercy, that he did not learn what was about to happen to his seed collection.
As it came to pass, the pact between Stalin and Hitler evaporated in June 1941 when the Nazis marched into Soviet territory. By September they had reached Leningrad, but meeting heavy resistance, the Germans were unable to take the city outright, so they settled in for one of the deadliest sieges in modern history. With the city surrounded, food supplies dwindled, as did fuel for heating. All told, the siege lasted 872 days and spanned three Russian winters, with temperatures sometimes reaching as low as −40°C. Thousands died, at first from shelling and then from hunger and cold. And there, in the middle of it all, lay the All-Union Institute of Plant Industry, and in it, Vavilov’s seed collection.
According to a historical account written by Russian plant geneticist Igor Loskutov, more than thirty scientists died due to artillery fire in the early days of the siege. Some staff were able to escape Leningrad and managed to smuggle out whatever they could carry. But most of the collection could not be evacuated, so a small group of researchers remained behind to protect it. Days became months and months became years and still they stayed, working in shifts as they defended the seeds from rats, looters and the elements, which easily breached the damaged building. And while they went hungry, they refused to consume any of the seeds. They knew this collection contained the genetic history of crops and the future of agriculture. Before their friend and colleague Vavilov had been taken away, he had declared: ‘We shall go into the pyre, we shall burn, but we shall not retreat from our convictions.’ For their convictions, the researchers stayed the course. And so it was, in the presence of wheat, corn, rice, peas and more, that at least nine scientists starved to death.
Vavilov was never formally executed, but this, when all was said and done, was merely a technicality, a murderous trick of paperwork. While his colleagues endured the Siege of Leningrad, he was transferred to another prison where food was withheld and where it seems he, too, succumbed to starvation.
The facility where Loskutov now works was once the All-Union Institute of Plant Industry, but it is now named the N.I. Vavilov Institute of Plant Genetic Resources – in a city that itself was renamed from Leningrad to St Petersburg. The institute’s renaming is a sign of how, in time, Vavilov’s name was cleared and the importance of his accomplishments was recognised, as were those of his colleagues who had died or been exiled.
And as for the seeds, they’re still there. There are even some in packets marked with Vavilov’s own handwriting. It’s a good thing, too, because just as Vavilov predicted, we’re going to need all that genetic diversity. The future of our food security depends on it.