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

Warren, J. CABI PDF

3

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

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

Warren, J. CABI PDF

4

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.

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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

Warren, J. CABI PDF

8

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

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

Warren, J. CABI PDF

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

Warren, J. CABI PDF

1

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.

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