Medium 9781780645087

The Nature of Crops: How We Came to Eat the Plants We Do

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Have you ever wondered why we eat wheat, rice, potatoes and cassava? Why we routinely domesticate foodstuffs with the power to kill us, or why we chose almonds over acorns? Answering all these questions and more in a readable and friendly style, this book takes you on a journey through our history with crop plants. Arranged into recurrent themes in plant domestication, this book documents the history and biology of over 50 crops, including cereals, spices, legumes, fruits and cash crops such as chocolate, tobacco and rubber.

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1. Introduction, the nature of natural: What does domestication involve?: Peanuts, Rye, Tomato

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Introduction, the nature of natural

The entire raison d'être of this book is to try and ascertain why we eat so few of the plant species that are available to us on Earth. In attempting this feat the first chapter tries to establish whether our impoverished diet is a new phenomenon. The evidence suggests that our ancestral diets differed greatly between cultures and although some of these may have been more diverse than our own, many others would have been more monotonous. Throughout this book different elements of the problem are tackled by exploring crop biographies as case studies. In this first chapter this approach reveals that over the history of crop domestication, humans have successfully and repeatedly solved one of the most significant problems involved in transforming wild plants into crops, which is how to avoid being poisoned. This was achieved by a number of methods: by selecting plants that contain lower levels of toxic chemicals, by adapting our own biology to be better able to digest these new foods stuffs and finally by inventing methods of processing plant materials which make them safer to eat. These issues will re-emerge and are covered in greater depth in subsequent chapters.

 

2. Wild things: Recently domesticated crops and crops that have returned to the wild: Cranberries, Huckleberries, Currants, Kiwifruits, Cacao, Cashew nuts, Pistachio nuts, Cabbages

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Wild things

What is the difference between a crop and a wild plant? The definition is not a black and white one. In this chapter we discover that many crops hardly differ from their wild ancestors, while others have slipped from our diet and returned to the wild. Even after thousands of years of cultivation, many crops are still grown alongside wild progenitors of the same species with genes regularly flowing in both directions. Modern genetic tools are revealing that some crops have been domesticated on several occasions.

In extreme cases, species that have been cultivated for millennia also occur as varieties that have just been plucked from the wild.

In the early days of the Soviet Union, the Russian scientist Nicholai

Vavilov realized that most of the world’s crops originated from a handful of ancient centres of domestication. Conversely, the great landmasses of

Australia and North America had contributed very little to our modern diet, except for a few minor players, which are in essence still wild species, such as macadamia nuts and cranberries respectively. These

 

3. Learning to live with exotic sexual practices: How plant breeding systems limit domestication: Vanilla, Beans, Figs, Hops, Avocados, Papayas, Carrots

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Learning to live with exotic sexual practices

Why are there so many species of flowering plants? The answer to this question is still hotly debated. Since the time of Darwin one of the leading theories has argued that plants have speciated by becoming genetically isolated from each other as a consequence of their individual relationships with unique species of co-evolved insects which pollinate their flowers. Insect pollination ensures that populations of plants can be genetically as separated from each other as if they were growing on different islands in the Galapagos. In this chapter we will discover that the bizarre pollination process found in many plant species has made them challenging to domesticate. This is because the necessary insect pollinators are not available widely enough or abundantly enough to allow the potential crop to be cultivated away from its home range or in sufficient quantity.

Plants so often do the most amazing things that we take them for granted. Some trees have the ability to live for thousands of years. It is entirely possible that olives are still being harvested from trees that Christ picked fruit from more than two thousand years ago. Similar things may also be true of plants that reproduce vegetatively. Although lacking the majestic grandeur of a tree, crops that regenerate from tubers may also technically live for many hundreds of years; but you would not recognize a geriatric potato if you saw one. Over evolutionary time, some species of plant may significantly increase the number of chromosomes they contain, through doubling, hybridization, or just the duplication or splitting of single chromosomes. In other plants, the amount of genetic material they

 

4. Storing up trouble: Plants with storage organs: Cassava, Yams, Potatoes, Taro, Akees, Onions

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Storing up trouble

Why do so few crops provide us with most of our calories? It is remarkable that we eat very few species of the plants that are available.

However, it is even more astonishing that we gain most of the energy we need to survive from a tiny sub-set of these species. This chapter explores this conundrum and finds that energy rich plants tend to contain toxins, and perhaps surprisingly, therefore, some of our most important crops have a propensity towards being poisonous.

In our modern world it is easy to be blissfully unaware of the most important challenge that species face. Although the solution to this problem may now seem trivial, for most of our history we have shared this challenge with plants and animals alike. In solving this dilemma for themselves, plants have frequently also provided us with a solution, while simultaneously creating a whole new set of difficulties for us to deal with.

The conundrum is ensuring that you have enough food to survive through lean seasons. The evolutionary struggle to eat and avoid being eaten has been highly influential in determining which plants we have domesticated, with different groups of crops providing us with sustenance and others helping protect this food from other hungry species competing to consume the same stores.

 

5. The weird and wonderful: Herbs, spices and crops with exotic phytochemicals: Wasabi, Chillies, Saffron, Herbs, Willow, Tobacco, Cannabis, Durians

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The weird and wonderful

Although we gain most of our calories from a remarkably short list of species, our spice-racks, and medicinal and recreational drug cabinets in contrast are stuffed with the plants that are rich in an amazing diversity of chemicals. This chapter describes a range of the more unusual plants that we consume and tries to answer: why are we repeatedly drawn to minor crops that burn our lips and befuddle our brains?

It can be argued that all plants with the exception of grasses can be considered to be poisonous. The cells of plants contain a vast array of weird and wonderful chemicals. The biological function of many of these within these plants remains uncertain. However, once inside the human body these compounds may act as powerful drugs, potentially enhancing our health by mopping up cancer causing reagents, or they may help kill disease-causing microorganisms. Alternatively nature’s apothecary may impair our well-being. Plants may cause our demise by rapid poisoning, or slowly cause our death over decades. Other chemicals derived from plants cause allergies, intense burning sensations and befuddle our minds.

 

6. Accidents of history: The role of chance events in domestication: Strawberries, Wheats, Bananas, Citrus, Rhubarb

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Accidents of history

Some crops seem just too good to be true. How on earth did our ancestors manage to develop bananas that don’t contain seeds? Or hybridize unrelated species to produce totally novel crops? This chapter covers a number of crops that have been created by our habit of growing related plants together and thus enabling them to unintentionally cross-pollinate each other. We also discover that although mutations are incredibly rare in nature, if you grow enough plants generation after generation, this random process can hit the jackpot and be responsible for the creation of new crops.

Humans have been domesticating crops for around 10,000 years. But not until 1900 and the rediscovery of Gregor Mendel’s experiments with breeding peas, did we have any real understanding of the laws of inheritance. In fact, it was as late as 1676 when plant anatomist, Nehemiah

Grew addressed the Royal Society that we started to appreciate that plants actually indulge in sex. In other words, for the vast majority of agricultural history we have not really had much of a clue about what we have been doing. The process of domestication has been one of simply identifying the most desirable or just unusual plants and propagating them.

 

7. Classic combinations and recurring themes: Plant families that have been repeatedly domesticated: Grains, Legumes, Pumpkins, Spinaches

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Classic combinations and recurring themes

We have seen that the chance of a wild plant being domesticated is rather rare. However, a small number of plant families have independently provided us with important crops on several occasions. This chapter tries to identify what makes these families so special. It appears that each of these families produces seeds or fruits that are easily stored, or leaves that can be harvested over a prolonged season. In addition to this, it turns out that their nutritional properties and agricultural requirements perfectly complement each other.

It is said that humans consume every part of the pig, except for its squeak. Although the hog may be a versatile creature, the ways in which we utilize plants are far more varied. In spite of the fact that we routinely eat so few of the plant species that are available to us, we have found a seemingly endless list of ingenious uses for every plant product on offer.

We dig up roots and underground storage organs, while fruits and seeds are devoured with relish. Plant sap is tapped to turn into rubber, or poured over pancakes as maple syrup or fermented to make birch sap wine. More viscous plant secretions give us varnish, glues and violin resin. Unopened flower buds provide us with the very different flavours of cloves and capers plus the rather less exotic tasting cauliflower. The stigmas and styles of crocus flowers are harvested to give us the spice saffron, and nectar is plundered from agave flowers to produce a range of desserts. The bark of trees provides us with items as diverse as cork, cinnamon and materials for building canoes. We use fibres from cotton and linen to make fabrics that are dyed using plant pigments. The fluffy fibres that

 

8. Ownership and theft: How the economic value of crops has influenced their domestication: Breadfruits, Sugarcanes, Cloves, Rubber, Tea, Coffee, Mulberries, Monkey Puzzles, Artichokes, Pineapples

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Ownership and theft

By weight, plant products are some of the most expensive commodities on earth. You might expect therefore that this would have driven us to domesticate many more crops than we have. However, the reverse is probably true. This chapter includes several examples where crops have become so valuable that this has fuelled economic self-interest in those involved in growing and trading in these crops. This in turn has driven them to steal, smuggle, outlaw and even destroy these plants, to an extreme that has been damaging to our crop genetic resources.

Everywhere you look there are plants. Without plants there can be no animals and certainly no humans. We don’t just eat plants. While doing so; we sit on chairs made of plants, eat at tables made of plants, and live in homes built of plants. We clothe ourselves in plant fibres. They are used to make musical instruments and most of our great literature and art was produced on plant material, coloured with plant pigments. We ferment plants to produce alcohol. Chemicals derived from plants make us high and are also still the basis of most of our medicines. The list goes on and on. And yet, we still utilize a tiny proportion of the plants that are available to us. Not only are plants essential for most human activities, the crop plants that we exploit in so many diverse ways are the rare elite. This can make them incredibly valuable and the people who control their cultivation and trade exceedingly rich and powerful. It is no great surprise therefore that human history is bursting with stories of subterfuge, stealing and smuggling of crops plants. Breaking monopolies of supplies of crops frequently motivated the great journeys of discovery such as those of

 

9. Fifty shades of green: Nutrient rich crops and the next generation: Clovers, Ryegrass

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Fifty shades of green

This final chapter identifies the fact that we appear to have preferentially domesticated plants from highly nutrient rich habitats. Neither this observation nor the role of pollination strategy had previously been considered to be important in the history of crop domestication. Earlier attempts to explain why we rely on so few crop species have argued that the limiting factor has been the availability of suitable plants. Here I conclude by proposing that what limits the number of species that we currently grow and consume, is our own imaginations, prejudices, traditions and vested interests. If this is true, in the future we may enjoy a whole myriad of new fruits and vegetables that are better for our health, and less demanding of the world’s limited resources.

It is frequently but apocryphally claimed that Eskimos have 50 words to describe snow. Closer to reality, but almost never quoted is the observation that there are 45 words for shades of green in the Icelandic language. In fact in most languages there are many more words to differentiate shades of green than there are for any other colour. This is because we live on a planet dominated by the colour green, where the forces of natural selection have equipped our species with eyes that are particularly sensitive to light in the green sector of the spectrum. We have evolved as botanists with acute abilities to differentiate plant species.

 

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