A couple of millennia before laughing Martians helped to make dehydrated instant mash popular in Britain, the ancient Andeans had hit upon this method of preservation. It helped that they lived, essentially, in a freezer – at least, once the sun set. By night, potatoes were laid out on the ground, to freeze. During the day, they’d thaw out and would be trodden on, to squeeze out water. Then they’d be left out to freeze again. After three or four days and nights the potatoes were transformed into chuño – freeze-dried potatoes. As well as dehydrating the tubers, this processing would also drive out glycoalkaloids from the chuño, making it less bitter than fresh potatoes. While domestication would have involved the selection of the most palatable potatoes – and this probably started before cultivation – some potatoes remained a little too bitter. Another way of reducing bitterness was to eat the potatoes with clay, which binds to the glycoalkaloids. Around Lake Titicaca today, there are still some Aymara people who eat their potatoes this way. Perhaps even more importantly, making chuño transformed potatoes into a form that could be stored for extended periods, sometimes years. While the elite amongst agricultural societies in the Fertile Crescent grew wealthy by amassing stores of wheat and herds of cattle, the Inca chiefs grew rich and fat on their stores of dried potatoes. Chuño became a currency in its own right – the peasants paid their taxes in it, while labourers and mercenaries were paid in it.
By the time of European contact with the Americas, domesticated potatoes were widely grown in western South America, from the Andean altiplano down the Chilean lowlands. And as the Spanish moved in to South America in a more aggressive way, they came to understand the value of chuño. High in the Bolivian Andes, 4,000 metres above sea level, they found a mountain so full of silver that it became known as Cerro Rico, the ‘Rich Mountain’. The Inca had mined it for centuries. For the Spanish, it was an unmissable opportunity. The treasure that Columbus had dreamt of was here for the taking. As the mines poured forth silver, a town grew up at the foot of the mountain: Potosi. It became the site of the Spanish colonial mint, and in the sixteenth century 60 per cent of the world’s silver came from there. At first the Spanish sent Native Americans down the mines – some conscripted, some there to earn a wage – but the work was dangerous and life-limiting. As the indigenous labour force dwindled in the seventeenth century, the Spanish mineowners switched to bringing in African slaves, tens of thousands of them. And they were fed on chuño. Translating the energy stored in potatoes into an unimagined bounty of silver, the Spanish flooded the European markets with the precious metal.
The Andean silver arriving in Europe fulfilled the promise of the New World – fabulous riches really were to be found there. But in the depths of the Rich Mountain, the price was paid for dearly in human life and misery. And the suffering didn’t stop there. The influx of silver into Europe fed inflation and destabilised economies. Meanwhile, the food that had fuelled the mines was also making its way over to Europe. Potatoes were coming to the Old World.
But which of the closely related subspecies of Solanum tuberosum – the high Andean or the low Chilean – was first introduced to Europe? Unsurprisingly, there have been proponents for both. These two cultivars vary quite subtly in their physical characteristics – the Chilean varieties have wider leaflets than the Andean. But it’s the adaptations to geography and climate which are most important. More crucial than altitude and temperature, it’s adaptation to latitude that’s critical here.
Potatoes from the Andes, from modern-day Colombia, had evolved in a place relatively close to the equator, where they’d become used to twelve hours of daylight. For these potatoes, moving to a more seasonal latitude would have been challenging. It was not so much the short days of winter that would have been a problem, but long summer days. Too much daylight inhibits the formation of tubers. But Chilean cultivars – growing further from the equator – would already have adapted to relatively long hours of daylight in the summer.
Plant physiologists have elucidated the factors controlling tuberisation. The leaves of the potato plant detect sunlight and length of day, and send out chemical signals which affect the development of roots and tubers. Some of the essential chemical signals have been identified. There’s a phenomenon in molecular biology (and astronomy) where the first compounds (or celestial bodies) to be discovered are often given quite genial names. Then the imagination of the scientist is stretched too far, and subsequent molecules (and stars) are assigned a string of letters – usually an acronym harking back to the longer names of related compounds – and numbers. So tuberisation involves a panoply of players, from phytochrome B, gibberellins and jasmonate to miR172, POTH1 and StSP6A. You may be relieved that I have no intention of spending the rest of this chapter describing the entire process and our present understanding of its molecular basis. (You may also be disappointed, and I’m sorry – but it’s not that type of book.) Suffice it to say, the physiology of tuberisation is impressively complicated. So we have a familiar conundrum – how do you alter part, or many parts, of this machinery without derailing the process entirely? And what are the chances of a random mutation popping up to do just the thing which would prove to be of benefit as potatoes spread further into temperate latitudes?
Even with everything we now know about how evolution works, this still seems to be something of a philosophical sticking point. But it’s not an insuperable hurdle – it can’t be, because we know potatoes have done it, somehow. We know that small changes to certain genes can alter the role of particular key players in biochemical pathways. Genes with such important, fundamental roles are often called ‘master control genes’. The proteins they encode, known as regulatory factors, act as molecular switches – turning other genes on or off, or more subtly controlling how strongly a gene is expressed. So it’s possible for a minor alteration in one gene –encoding one of these important molecular switches – to have significant and widespread effects. Even though evolution, at a genetic level, works its magic through tiny changes, some of those tiny changes can have profound, far-reaching consequences for the phenotype – the structure and function – of an organism: evolution can make sudden jumps.
There’s a good candidate for just such an important molecular switch – or regulatory factor – in potato tuberisation, meaning that a tiny alteration really could result in a pronounced physiological change. The variation that already exists within populations represents an important part of the solution too. A species is not one organism, one genome. It is the sum of all of its parts, and those parts vary. As potato-farming spread southwards, into latitudes with longer summer days, some potatoes would have been better able to produce tubers than others. In a more temperate climate, those variants would have had the edge. Natural selection would weed out the rest.
Given these adaptations to latitude, it seems likely that Chilean potatoes would have stood a better chance in Europe than their more equatorial counterparts from the northern Andes. In 1929, Russian botanists proposed precisely this origin for the European potato. But British researchers were sure that the original European potatoes hailed from the Andes. Historical records suggested that potatoes arrived in Europe at a time when the Spanish were barely established in Chile, whilst having conquered countries around the northern Andes – Colombia, Ecuador, Bolivia and Peru – half a century earlier.
Many botanists believed that the balance of probability lay in one particular direction. For the last sixty to seventy years, the prevailing hypothesis has followed that British suggestion – that European potatoes descended from northern Andean stock. This hypothesis seemed strengthened by the fact that ancient varieties of potatoes in the Canary Islands and in India looked as though they harked back to northern Andean roots.
Then the geneticists got involved, and – as they tend to do so often – set the cat among the pigeons. The Canary Island potatoes turned out to contain a mixture of Chilean and Andean heritage. The Indian potatoes were quite clearly of Chilean origin.
Th
eir interest aroused, the geneticists moved on to look at mainland European potatoes – undertaking genetic analyses on historical samples from herbarium collections dating to between 1700 and 1910. The eighteenth-century potatoes of mainland Europe proved to be of largely Andean heritage. They must have had to adjust quickly to long summer days. Perhaps this was due to rapid adaptation – brought about by something like a novel mutation occurring in a particular, master molecular switch, producing widespread effects. In fact, such a mutation need not have been entirely novel – long-day variants may have already existed in those newly imported Andean potatoes; we know that this characteristic pops up from time to time in those varieties. Maybe the adjustment to temperate latitudes wasn’t quite as challenging as had once been thought.
But that wasn’t the end of the story. In samples from 1811 onwards, the geneticists found evidence of Chilean ancestry in European potatoes. Some previous researchers had suggested that Chilean varieties had been introduced after blight epidemics had swept through the earlier, northern Andean stock, starting in 1845. There was always a problem with this hypothesis, as Chilean potatoes are not especially resistant to blight. Nevertheless – for whatever reason – Chilean varieties had clearly been introduced to Europe in the nineteenth century – and they quickly became very successful. Although the Andean varieties were the first to be established in Europe, Chilean potatoes seem to have had an inbuilt advantage, perhaps drawing on their deep history of growing somewhere where summer days were long – it’s their DNA which predominates in the European varieties we grow today.
Carmelite friars and a bouquet of potato flowers
As for how potatoes arrived in Europe in the first place, you may be fairly sure that Columbus brought them back from the New World, just as he did with maize. But it’s not true. Although Columbus and other adventurers did ship many foods back to Europe in those early days of contact with the Americas, the potato was not among them. And this is because it was cultivated on the western side of South America – from the mountains down to the Chilean lowlands – and the Spanish did not reach the High Andes until the 1530s, some forty-odd years after Columbus’s first explorations across the Atlantic. The first written report of potatoes came from Spanish explorers in 1536, who found them growing in the Magdalena Valley of Colombia.
As a further complication, there is no historical record of the first arrival of potatoes in Europe. Whoever received them on this side of the Atlantic obviously did not deem them particularly worthy of note. Or perhaps they did, and their exhilarating account has somehow been lost to history. There’s also a linguistic complication: sweet potatoes (Ipomoea batatas) are batata in Spanish, while Solanum tuberosum is patata. However, the first published reference to what really does seem to be a potato appears, in Spanish literature, in 1552. Soon after, there are records of potatoes in the Canary Isles. The first mention of potatoes actually appearing in Europe – as an import, rather than a crop – dates to 1567, when there’s a record of them being shipped from Gran Canaria to Antwerp.
(Forgive me a little detour here. There is apparently a heated debate about who really invented French fries: the Belgians or the French. Both countries claim priority, with the Belgians blaming ‘French gastronomic hegemony’ and geographically challenged American soldiers for the naming of this particular delicacy. The first documentary evidence of such treatment of potatoes is apparently Belgian, and dates back to the late seventeenth century, according to unverified journalistic sources. On the other hand, the very first documentary evidence of potatoes reaching the European mainland is that consignment making its way to Antwerp. We have no way of knowing what the Belgians actually did with those potatoes. But I like to think that someone in Antwerp, 450 years ago, may just have invented what almost became a national dish. Until the French stole it, anyway.)
Just six years after that first mention of potatoes in Europe, there’s fairly firm evidence of cultivation, in Spain. The 1573 accounts of the Carmelite Hospital de la Sangre in Seville describe potatoes being bought in the last quarter of that year. This strongly suggests that the potatoes were locally grown, seasonal vegetables. It also points to potatoes being grown in the autumn – in a growing season with short days, then, which would have suited Andean varieties admirably. Very much like Caribbean maize, potatoes hailing from tropical latitudes (regardless of altitude) in the Americas seem to have settled in relatively easily to southern, Mediterranean Europe.
Once the potato had gained a toehold in Spain, it spread quickly to Italy – introduced there by Carmelite friars. And then, again rather like maize, this exotic vegetable began to disperse through the botanical gardens of Europe, making its appearance in herbals written in the late sixteenth century. The Swiss botanist Gaspard Bauhin gave it its Latin name, Solanum tuberosum – ‘the soil-bound swelling’. The English botanist John Gerard – who thought that one variety of maize came from Turkey – was equally confused about the origin of potatoes. He was so sure the potato had come from Virginia that he named it Battata virginiana. And thus, he sowed the seeds of the legend that Sir Walter Raleigh brought potatoes to England from his colony in the New World. Another legend, that Sir Francis Drake transported potatoes from Virginia to England, is equally devoid of any basis in fact.
Having been introduced and spread within Europe via seemingly elite networks that involved the Catholic Church, potatoes appear to have been enthusiastically adopted by the peasantry of Italy, who by the beginning of the seventeenth century were eating them alongside turnips and carrots and also feeding them to pigs. Meanwhile, potatoes were spreading eastwards too, reaching China in the same century. Within the Americas, the northwards expansion of the Spanish Empire saw the introduction of potatoes to the west coast of North America. Potatoes also made their way back from Europe, across the Atlantic, with British traders and migrants. By 1685, William Penn was able to report that potatoes grew well in Pennsylvania.
But the craze for potatoes was slow to spread north in Europe. The reasons for the late adoption of this seem to include some deep-rooted but rather odd superstitions. Potatoes, perhaps because of their odd, misshapen tubers, like deformed limbs, were linked to leprosy. The fact that potatoes were not mentioned in the Bible was also a source of suspicion. The similarity of potatoes to deadly nightshade caused consternation, and perhaps this wasn’t an entirely undue worry. Once potatoes turn green, and start sprouting, the levels of solanine in them are enough to be quite toxic. That’s why it’s so important to keep potatoes in the dark. Learning how to store potatoes safely would have been crucial to avoid being poisoned by them. Other concerns about potatoes included possible flatulence and an increase in lust, hopefully not at the same time. And beyond that, there was a general aversion to eating potatoes in many countries where they were first adopted as a crop destined to feed animals. When, in 1770, a boatload of potatoes was sent as famine relief to the starving inhabitants of Naples, they rejected it.
Beyond the taboos and superstitions, there may have been a more prosaic reason for the slow acceptance of the potato in northern Europe. From a purely functional point of view, it was tricky to slot potatoes into the three-year crop-rotation system that had been practised across Europe since Roman times. It was awkward for individual farmers to make changes in one of their strips, within a larger field that they shared with the other farmers in the village.
Eventually, the cultural barriers to potato expansion came, if not crashing, then at least crumbling down. A curious mix of religion and politics finally conspired to propel potatoes, from southern Europe, northwards and eastwards. In the late seventeenth century, the Huguenots and other Protestant groups were expelled from France, taking their expertise – in areas as diverse as silversmithing, obstetrics and potato cultivation – with them, wherever they went. In the mid-eighteenth century, the fallout from the Seven Years’ War demonstrated another advantage of the potato: lurking underground, this crop – unlike cereals – could survive in fields that h
ad been burned and trampled. When Antoine-Augustin Parmentier, a pharmacist in the French Army, was caught by the Prussians, he was fed potatoes in his cell. Rather than baulking at this treatment – after all, he was only familiar with potatoes as fodder for livestock – he was impressed by the nutritional value of his prison fare. When he returned to France in 1763, he became a vociferous proponent of potatoes. He hosted potato-based dinners for the great and good, and gave bouquets of potato flowers to Louis XIV and Marie Antoinette. But it was a run of poor harvests, revolution and famine which eventually secured the place of this humble tuber in French cuisine. Today, Parmentier’s pioneering spirit is remembered in the name of many French dishes, all of them involving potatoes in some form or another. His grave in Paris is ringed with the plants he loved so much.
Helped by Parmentier in France, and other champions including Frederick the Great in Germany, and Catherine the Great in Russia, potatoes broke out of the monasteries and botanic gardens, into the fields of the northern European plain. Potatoes began to replace traditional staples and fallback foods such as turnips and rutabaga, providing a real alternative to the sometimes risky reliance on cereals that had gone before. Famines still hit from time to time, but less frequently now that there was another staple to fall back on. Together with that other American import, maize, potatoes helped to support an astonishing growth in the European population, which almost doubled in the hundred years between 1750 and 1850, from 140 million to 270 million. Potatoes – once the fuel of the Inca Empire – now provided a huge economic boost to the countries of central and northern Europe – providing energy for a growing population, and underpinning urbanisation and industrialisation. While the steam-powered machines of the Industrial Revolution were fed on coal, its workforce was powered by – cheap, dependable, plentiful – potatoes. The balance of political power in Europe began to shift, from the warmer, sunny countries of the south to the colder, greyer states of the north. The factors behind the rise of the European superpowers in the eighteenth and nineteenth centuries are many and complex, but somewhere in there, darkly lurking, is the potato. And it was there in the crises of the twentieth century – forming an important provision for armies. Second World War military rations included that old Andean trick – dehydrated potatoes.
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