杏吧原创

HUMAN life often seems a frenetic business, all booming population and
burgeoning technology. Where, amid all this chaos, do we place plants? In some
parts of the world, where most of the people must wrest their living from the
soil, the importance of plants for food, clothing and shelter is still
recognised as paramount. It鈥檚 in the developed world that plants can seem
peripheral鈥攄ecorative in the garden, enjoyable as food, perhaps, but not a
lot more.

Yet it only takes a little thought to see that plants are of vital importance
to all of us here and now, harnessing the energy of the Sun through
photosynthesis, making that energy available to us as food, and giving out
oxygen for us to breathe (Figure 1).
And plants mean even more. Over thousands
of years they have helped to shape our cultures and societies and entwined
themselves through our economics and politics. Some have been seen as so
valuable that they鈥檝e actually changed the course of human history.

Food for thought

Eating your greens

Without plants, there would be no human history鈥攐r prehistory鈥攁t
all. They have underpinned our diet from the very beginning. Globally, much of
the staple diet of the human race comes from products of plant
reproduction鈥攆ruits, and/or the seeds that they contain. Plant food can
provide us with carbohydrates, proteins and fats, as well as fibre (which cannot
be digested but which helps the working of the gut) and many of the minerals and
vitamins needed for health. Add to this the fact that most animals eaten by
people have themselves eaten fodder plants such as grass, and the vital support
to human life provided by plants becomes clear.

The great cereal crops of rice, wheat, maize, oats and barley all had
their genesis in wild grasses. For generations they have been selected and bred
to increase their yield, to help them thrive in different conditions in various
regions, and to make them as resistant to disease as possible. Now they are
being genetically engineered to develop other traits, enabling crops to make
their own pesticides, or to indicate when disease or pest damage occurs.

Some of these cereals, such as rice, are cooked and used whole. Others, like
wheat and maize, are ground into flour and then used to make bread and other
foods. Seeds contain a store of energy for the developing embryo, so cereals are
a very good foodstuff for people, providing them with plenty of carbohydrate,
some protein and small amounts of other valuable nutrients.

Cereals aren鈥檛 the whole story, however. Oil is extracted from some
seeds, such as sunflower, linseed and oil seed rape; then there are
nuts, and pulsessuch as beans, peas, lentils, soya beans and
chickpeas, which provide much of the protein requirement for the global
population. Fleshy and succulent fruits are vital, particularly for their
vitamin content. Apples, bananas, tomatoes, raspberries, mangoes, oranges,
breadfruit鈥攖he list of berries and fruits eaten by people all over the
world is a long one. Fruits were probably also an important part of our earliest
ancestors鈥� diet, as were roots and tubers. Carrots, sweet potatoes, beets and
other roots are staples still eaten all over the world. And it鈥檚 well
known that a single tuber鈥攖he potato鈥攈ad a profound effect on
European and American history (see 鈥楩amine, Disease and Blight鈥�).

So far, we鈥檝e only set half the table鈥攚hat about drinks? Apart from
water, almost every liquid we consume depends directly or indirectly on plants.
Even milk, whether from cows, sheep, goats, mares or camels, is produced from
the plants on which the animals have grazed.

To make beverages, different parts of different plants are used in one of
three basic methods. Fresh or dried leaves are infused in boiling water; fresh
or roasted seeds are ground up and infused in hot water; or seeds or fruit,
ground or mashed and sometimes mixed with water, are then allowed to ferment,
forming any of a number of alcoholic drinks. All three types of drink have been
hugely important in human history: you have only to think of tea, coffee and
wine.

Interestingly, the plant products used to make hot nonalcoholic drinks all
produce quantities of stimulants鈥攖ake caffeine, which occurs in
both tea (as theine) and coffee. This explains some of their popularity,
but there is another reason. In the 17th and 18th centuries, when the
consumption of nonalcoholic drinks took hold in Europe, hygiene was dubious.
Waterborne diseases were so widespread that water was often boiled before
drinking鈥攁nd anything that gave it both flavour and stimulative qualities
was obviously very welcome. The only alternative was alcohol powerful enough to
kill any germs, which was an impractical option, as people do not work, learn or
function properly if they are constantly drunk.

So tea, coffee and chocolate became the big three of European
beverages鈥攆irst as the coveted preserve of the rich, then gradually
spreading to all sectors of society. Amazingly, all of them arrived in London in
the same year鈥�1652. By changing the daily habits of millions of people,
they created tremendous demand and trades that took Europeans all over the
world, and would have far-reaching consequences (Figure 2).

Chocolate, made from the cacao bean (Theobroma鈥攐r 鈥渇ood
of the gods鈥濃�攃acao), came from Central America, where in
pre-Columbian times the bitter liquid made from it was flavoured with chillies
and vanilla. In the 17th century Europeans began to drink it mixed with
sugar.

Cups that cheer

A world of trade

Coffee is produced from another sort of bean鈥攖he roasted and ground
seeds of the arabica coffee bean, which originated on the Horn of Africa.
Caffeine is not only highly stimulative; it is also addictive鈥攄oubtless
part of the reason for its popularity. It was and is permissible for Muslims to
chew coffee beans, a practice that began with the Arabs back at least as far as
the 7th century. The beans were first turned into a drink by the Turks, and
coffee spread across the whole of Europe in the 18th century. Only wealthy
Europeans could afford to drink it until after the Second World War, when huge
quantities of the robusta bean from Brazil became available, and coffee
drinking鈥攁nd its attendant addiction鈥攕pread through Europe and the
US. Later, instant coffee boosted consumption even more. Coffee is now the
second most valuable exported commodity on Earth.

Tea, in its brewable form, is made from the leaves, buds and flowers
of Camellia sinensis, which after gathering are dried and blended.
Originally grown in China as long ago as the 3rd century BC, the crop is now
cultivated in other Far Eastern and Asian countries as well as the Middle East,
Australia, Latin America and the US, and tea is drunk in one form or another
almost everywhere.

Of Europe鈥檚 big three, tea has arguably triggered the most profound social
and economic changes. The tea trade arose out of the activities of the East
India Companies, groups of European merchants who, starting round the end of the
16th century, sailed the seas in search of valuable commodities. They bought the
tea in Canton, where the Chinese demanded to be paid in silver鈥攁 practice
that led to massive inflation as silver prices in Europe climbed. The rise in
tea drinking exacerbated the situation: in 1801 each person in England alone
consumed more than a kilogram of the stuff, along with an astonishing 8
kilograms of sugar. So the East Indiamen had to discover something that the
Chinese would value鈥攐r covet鈥攅ven more than silver.

They found it in opium. This highly addictive drug, produced from the
opium poppy, had been illegal in China since the early 18th century; yet
European merchants found plenty of their counterparts in China willing to
provide tea in return for opium grown in India. By 1830 the British were
exporting some 1.5 million kilograms of it to China annually鈥攚orth
$1 billion a year in today鈥檚 money. The flood of opium left millions
addicted, nearly destroying Chinese society, and led to the 1840-42 Opium War
between Britain and China. From then on China was forcibly opened up to trade,
and the great cultural and intellectual heritage of the country was ravaged.
Opium ruined China, which had been many centuries ahead of the rest of the world
in inventions and technology, and it laid open the way for the communist
uprising of the 20th century.

The influence of tea on human history did not stop there. Europeans,
including the British, introduced tea plants to India, Sri Lanka, Indonesia and
Africa鈥攔egions where most of the world鈥檚 tea now originates. In India, the
introduction of tea changed the habits of a nation. Before 1840, tea-drinking
was virtually unknown there, yet now India is the greatest producer of tea in
the world鈥攁nd two-thirds of that produced is for home consumption. The
leaf also played a starring role in the build-up to the War of Independence in
America. In 1773 a group of colonials objecting to British taxes on tea dumped
the cargo of three tea ships into the harbour of Boston,
Massachusetts鈥攅nacting the famous Boston Tea Party.

All very stimulating鈥攂ut what of alcohol, at the more relaxed
end of the spectrum? Alcoholic drinks have been part of human history almost
back to the dawn of time, and have been made from an enormous variety of plant
products. Modern wines are made from a wide variety of grapes, but people have
made wine with cowslips, parsnips, nettles鈥攅ven marrows.

In the process of fermentation, the natural sugar contained in the
plant is used for respiration by added yeasts, and the waste products they leave
are carbon dioxide (sometimes used to produce sparkling wine) and ethanol. Beers
are brewed using malt, or treated barley, and hops; the mixture is heated
to boiling point and cooled before the yeast is added. Spirits are
distilled鈥攁 process that involves heating, cooling and condensing.
Vodka is made from grain or potatoes, rum from sugar cane.

Alcohol鈥檚 role in human history has been mixed. On the one hand, these drinks
have oiled the wheels of social and business transactions for thousands of
years. On the other, they have caused enormous suffering through the violence,
crime and ill health their overuse can cause. After being introduced to alcohol,
societies such as those of certain Native American peoples and the Australian
Aborigines have been devastated; high levels of addiction to the
substance have nearly destroyed their cultures. Studies by the Centers for
Disease Control and Prevention, a US government body that monitors health and
quality of life, estimate that fetal alcohol syndrome鈥攊n which babies of
mothers who drink are born with facial deformities and learning
disorders鈥攊s three times as common among Native American peoples as among
the American population as a whole.

Clothes on your back

Labour-intensive job

We have looked at edible and drinkable plants. But you can wear plants,
too鈥攁nd not just as a Crusoe-like concoction of stitched leaves. The
structure of many plants is in part tough cellulose fibres, which may run
through the stems and leaves, or be part of the seed dispersal mechanism. Hemp,
jute, manila, flax and sisal are just a few examples. For centuries people have
used them in different ways鈥攁s rope, as material to write on, but most
importantly as the raw material for cloth.

Probably the best known and most widely used of these is cotton. To
produce cotton fine enough to wear was an enormously labour-intensive task at
the end of the 18th century. It took up to 14 person-days of labour to produce a
single pound of cotton thread鈥攁nd that still had to be woven into cloth!
It took about 3 person-days to make the equivalent weight of wool or linen, and
only 6 to make a pound of silk. So in those days cotton was a luxury fabric.

But by the 19th century the Industrial Revolution had speeded up and
mechanised the processing of cotton enormously. As a result, the demand for
cotton spiralled. By 1861, the year the American Civil War began, cotton had
become the single most important crop traded worldwide, and up to 80 per cent
was grown in the American South. Just as with other valuable crops such as tea,
greed for profit began to degrade and destroy societies.

The cotton-growing farmers of the southern US ran their farms using black
slave labour. Between 1784 and 1861 the number of black slaves in the US
increased eightfold, and almost all of them were employed by the cotton
industry. In 1808, just as the need for more workers was growing, it was made
illegal to import any more slaves. So 鈥渂reeding鈥� slaves was seen as necessary by
the deluded and dehumanised cotton plantation owners, who counted their slaves
among their livestock and grew rich (Figure 3).

As time passed and attitudes evolved, slavery gradually came to be seen as
unacceptable by whites, particularly in the industrialising North. But in the
South, the white plantation owners found it impossible to imagine life without
slavery. The American Civil War took slavery as one of its central issues and
freed 4 million slaves. It has, however, taken many generations for black
Americans to have the same rights as their white compatriots鈥攁 bitter
legacy of King Cotton.

As we鈥檝e seen, the tangible parts of a plant鈥攍eaves, bark, stems,
seeds, fruits鈥攁re all hugely useful. But all plants are also made up of
chemicals. Some are deadly poisonous. Digitalin in foxgloves, for
instance, can have a dramatic and fatal effect on the heart. And some鈥攖he
full range of plant chemicals which come into this category may never be fully
known鈥攁re remarkable allies in our systems of medicine.

Healing herbs have been used for generations all over the world to reduce
fever, halt infection and heal wounds. Often the chemical responsible would be
unknown; it was simply a case of knowing which herb does what. Now many of these
drugs have been isolated, allowing more precise dosing and better treatment.

Salicylic acid鈥攂etter known to most of us as aspirin
鈥攐riginates in the leaves of a species of willow. For centuries these
leaves were chewed or brewed up into a drink to relieve pain and fever. Now our
doses are carefully measured out鈥攊n a small white tablet! This represents
a major advantages of extracting and purifying the beneficial drugs found in
plants: you can give known repeatable doses of the chemical.

Levels of chemical present in any part of a plant will vary with the age of
the plant, the season, even the time of day. Partly because of this, enormous
amounts of plant material are used up when extracting the active chemical. It is
thus becoming more common to analyse the structure of beneficial plant
chemicals, then synthesise the drug on an industrial scale.

Along with hygiene, exercise and nutrition, our ever-increasing arsenal of
drugs is having an enormous impact on human health. People are ill less often,
they are less severely ill and they are living longer鈥攁ll factors
contributing to change in our societies, such as swelling numbers of the
elderly. Not only this: great tracts of the world that were previously closed
because of the diseases prevalent there have opened up for habitation,
colonisation or cultivation.

Curse of the tropics

Mind-altering drugs

One of the clearest examples of the impact plant-based drugs have had is the
treatment of malaria鈥攁 disease spread by the bite of the female
Anopheles mosquito, which passes on a blood-borne parasite. Over 350 years
ago the wife of the Spanish viceroy, the Countess of Cinchon, lay wracked with
malaria in Peru. Her doctor suggested the use of a native remedy for the
disease鈥攖he bark of the cinchona tree. The countess recovered, becoming
the first European on record to recover from the disease by taking quinine.

Quinine made it possible for Europeans to travel in the malarial
tropics. Indigenous peoples also used the magical drug to rid themselves of the
disease. It became a powerful trading tool鈥攖he Jesuit priests of Spain
used their knowledge of quinine to fill the coffers of the Catholic church and
enable missionaries to travel abroad in safety. The trade in Peru swelled
hugely, and along with it the destruction of the cinchona trees鈥攚hich by
1795 amounted to some 25 000 trees a year. But the pervading influence of the
Catholic church meant that many Protestant countries refused to buy or use
quinine. So, up to the end of the 18th century, British, Dutch and American
explorers, soldiers and settlers were denied the benefits of the wonder
drug.

There is a terrible irony in how quinine made travel possible in remote
places. One can travel in relative safety now in the Amazon basin, itself a
wondrous repository of plants, many potentially as valuable as cinchona. Yet for
decades, first explorers and now loggers and developers, have been busy
destroying this floral cornucopia.

Drugs themselves can be misused, too, as societies worldwide know to their
considerable cost. Even caffeine has well-documented adverse effects鈥攊t is
implicated in insomnia and in heart arrhythmias such as tachycardia, an
abnormally fast heartbeat. The death toll from some plants, however, is
positively terrifying. Tobacco is a case in point. Smoking and chewing
the dried and shredded leaves of the tobacco plant are practised almost
everywhere. The leaves provide people with the addictive drug nicotine,
but they also produce tar and other chemicals that are known to cause cancers of
the mouth, throat and lungs. Other chemicals from tobacco affect the circulatory
system and cause an increased risk of having a heart attack.

These facts are well known, yet millions of people continue to smoke, and
more and more young people are taking it up. The Centers for Disease Control and
Prevention report that in the US alone, about one in every five deaths arise
from smoking. And the WHO notes that globally, deaths related to tobacco use now
run at 4 million a year, and may increase to as many as 10 million a year by the
early 2030s (Figure 4).

Both alcohol and tobacco can be used legally in many countries of the
developed world. But many other addictive and psychotropic, or mind-altering,
drugs extracted from plants are illegal in almost every country. Some of them,
like marijuana, are relatively mild in their effects. But other
诲谤耻驳蝉鈥�cocaine from the coca plant, and the narcotics heroin
and opium from the opium poppy鈥攑owerfully affect the minds and
bodies of users. These 鈥渉ard鈥� drugs can cause death directly as a result of
overdosing, and indirectly by the lifestyle that often accompanies drug use:
prostitution to get the money to buy the drug, neglect of normal hygiene and
eating habits, and sharing needles. This last could mean sharing an infection,
for example HIV.

As we鈥檝e seen with the history of opium in China, such drugs touch not just
individuals but entire societies. Trade in illicit substances, like any trade,
involves suppliers and consumers. In this case the suppliers are people such as
the drug barons of modern South America, who are tremendously wealthy鈥攁nd
powerful. Equally powerful is the lure of the drugs, and more and more Western
youths are being drawn to them. Cocaine abuse has been a problem in the US
during the 1990s, and in England and Wales the British Crime Survey
1998has shown a rise in cocaine use among 20 to 24-year-olds from 2 per
cent in 1996 to 5 per cent in 1998.

There are many other stories to tell about plants鈥攖he phenomenal role
of sugar in world history, for example. Meanwhile, for food, drink, medicines,
and even the air we breathe, we depend absolutely upon them. So the next time
you pass a park or garden, spare a thought for the green stuff: it鈥檚 keeping us
all alive.

PERHAPS the most extreme example of how a single plant can affect society is the story of Ireland
and the potato. For centuries Ireland suffered from its difficult climate and geographical isolation
and remained technologically undeveloped: the people had only crude tools and methods for
ploughing and harvesting. When the potato reached Ireland in the late 16th century, it suddenly
meant that almost everyone could grow enough food for their families鈥攁nd the population exploded.
In 1760 there were 1.5 million people; by 1840, numbers had swollen to 9 million. So, despite enormous,
ongoing tensions between their country and England, which were partly to do with the
Protestant/Catholic divide, the Irish could at least feed themselves and their children well.

Over-reliance on any one support carries an in-built danger, however, and this was unleashed
on Ireland in 1845. Potato blight, a fungal disease (Phytophthora infestaris), struck the crop and
wiped it all out, all over the country. An estimasted 1 million people starved, or died from typhus, cholera
or other virulent diseases that followed the famine. More than a million Irish emigrated, many to
North America, setting a pattern for decades to come. The failure of one humble tuber had a long-lasting
effect on Irish history, as well as on the US, and the relations of both countries with Britain.
The potato, in fact, has caused as much suffering and political difficulty as any plant on Earth.