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CONTEXT

The article, plants & people, provides introductory commentary, discussion. and interpretation of this topic, while the timeline provides a chronological and synoptic overview. 

Plants & people

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‘Plants drink water, building their tissues by eating light and carbon dioxide and excreting oxygen. In this way they provide the chemical ingredients needed to sustain the entire community of life’

Anon.

or, as expressed more succinctly over 2500 years ago –

‘All flesh is grass’

Isiaah 40: 6

How can we explain and categorize the many ways in which the lives of humans intersect with those of plants?

This difficult question is often answered in a cavalier way under the heading ‘plants and people’ with discussion that would probably sit more comfortably under headings like ‘economic botany’, ‘plant cultivation’, or ‘Plant domestication”.  For many years this topic has been addressed by museums of economic botany that have treated it as a question about ethnobotany – the ways in which native peoples have used plants as dyes, fibres, medicines and tools as well as for ritual and art. But this cannot do justice to an interdependence that dates back to a time even before the origin of Homo sapiens.

This series of articles under the heading ‘plants and people’ looks critically at this subject and begins by placing the human-plant relationship within its broadest context – that of evolutionary time and planetary space. From this vantage point we can view the broad landscape of the topic before focusing on particular aspects and drilling into the detail.

Co-evolution

Considered over the long term it is clear that the relationship between humans and plants is not a one-way relationship, it is a reciprocal relationship, an interdependence. Significantly, this mutual dependence is only total in one direction: plants can survive without humans, but humans could not survive without plants. Humans have impacted the lives of plants by altering their genetic makeup and reconfiguring their distribution and species composition over the surface of the planet. But humanity’s total dependence on plants is demonstrated by their influence on both our biological and cultural evolution . . . by changing or biological and psychological makeup and constraining our historical modes of social organization. This is a relationship of co-evolution.

In very general and simplistic terms, plants have been a major source of life, health, wealth, and happiness. But how has that played out over the long term?

Humans lived first as Palaeolithic hunter-gatherers in wild nature with both their biological and cultural evolution strongly determined by factors in the natural environment. Then, as Neolithic farmers, it was cultural factors that increased in significance. Humanity had taken a giant step from a mode of existence dominated by nature to one constrained by culture as, superimposed on slow biological evolution there followed a period of rapid cultural evolution. In domesticating plants and animals, humans had adopted a sedentary way of life that changed their environments of both biological and cultural evolution. The result was modern civilization, and in this sense, humans were co-incidentally domesticated by plants. Humans whose bodies and minds were fashioned by adapting to natural wild environments, now live in artificial environments, a result of the greatly accelerated increase in social organization made possible by the energy of cereal grains and fossil fuels. This has created a new set of challenges, a new environment, for both biological evolution and cultural adaptation.

Gradually, through the first three phases of human existence (Natura, Agraria, Industria) six significant categories of economically important plants emerged: those used in everyday living (dyes, fibres, resins etc.), medicinal plants and spices, horticultural plantation crops, agricultural crops, forestry timbers, and the ornamental plants of horticulture (first clearly recognized in the agrarian cities of the Bronze Age). There is a further and more recent seventh category, the unintentionally introduced plants that have escaped from cultivation to naturalize in the wild across the world.

Energy

All activity needs energy, and the energy used for individual and collective human growth and development has, until recent times, come entirely from plants.

Human history may be divided into three major phases, each powered by the Sun’s energy stored in plant chemicals during photosynthesis. These three phases we can call natura, agraria, and industria. In each phase the direct energy absorbed from the food and powering individual human bodies has remained about the same. What distinguishes them  is the indirect energy needed for food production, manufacture, and social activity – in other words the energy needed to build social organisation. It is the discrepancy between these direct and indirect social energy use that has defined these three social transitions.

First came natura, the phase of nomadic hunter-gatherers when, for a period of about 55,000 years from c. 70,000 to 12,000 BP small tribes of 20 to 100 people during the Upper Palaeolithic until the world  population reached around 3 million (Morris 2015). These foragers lived within wild nature hunting animals, their plant diet consisting mostly of wild greens, fruits, seed, and root vegetables. During natura the social energy needed for fuel, clothing etc., hardly exceeded the average individual food energy requirement of about 1500 to 2000 kcal/cap/day.

Second came agraria, the phase of settled farming communities associated with domesticated plants and animals from about 12,000 BCE to 1500 CE during the Neolithic Agricultural Revolution whose settlements evolved into Bronze Age cities and civilisations which lasted for around 11,000 years until the population numbered about 450,000 million at the dawn of phase 3. During this second phase the diet was strongly supported by the energy stored in the grains of cultivated cereals and the meat of domesticated animals. The sedentary lifestyle and ready energy source facilitated population growth and the additional social energy needed for food production, rudimentary manufacturing and the building of settlements and eventually cities. Total energy consumption would have been around 6000 to 8000 kcal/cap/day (Morris 2015).

The third phase, industria, occurred around 1550 with the discovery of the concentrated fossil plant energy that could be harnessed from fossil fuels. This provided a windfall of social energy that facilitated unprecedented increase in social organisation manifest as a rapid acceleration in population numbers, manufacturing, technology, along with improved transport and communication that increased trade and global connectivity. We know this phase as the Industrial Revolution which has lasted about 470 years. Food energy was now achieved with energy-hungry industrial agriculture and extensive processing while social energy was eaten up in product manufacturing of many different kinds leading to energy-intensive lifestyles consuming up to 200,000 kcal/cap/day and more (Morris 2015). The result was a human population explosion during which today totals about 7.5 billion. This has been accompanied by a similar burst in the numbers of domesticated animals. The ‘MacCready explosion’ claims that 10,000 years ago humans, their pets and livestock comprised around 0.1% of terrestrial vertebrate biomass, today this total has rocketed to 98% (MacCready 2004). Though a statistic that must have been difficult to derive, even if remotely accurate it is indeed alarming.

Change in human lifestyle have occurred as a result of slow biological change or rapid cultural change. Let’s begin with our basic biology.

Plants & human biology

Photosynthesis first occurred about 3.5 billion years ago but the seed plants we are most familiar with evolved much later – conifers over 300 million years ago, and flowering plants about 125 million years ago. On the human animal side mammals date back about 200 million years, the great apes about 14 million years, the genus Homo about 2 million years and our species, Homo sapiens, about 200,000 years.

Unsurprisingly, since plants have always been a major part of the human environment of evolutionary adaptation (EEA), there are many physical and psychological traits that we can attribute to plants. These are discussed in the article Plants make sense). Simply by being living organisms there are many vary similar biochemical pathways held in common. However, the specific innate human traits that have been related to evolutionary plant influences include: bipedalism, stereoscopic and colour vision, dentition, the digestive system, taste (sweet and sour), the biology of smell, and lactose tolerance.

universal (innate) human biological traits including: bipedalism, colour vision etc. (see Plants make sense). In contrast humans have, for most of the evolutionary history of plants, had little impact on plant biology, partly because of the relatively brief period of plant evolutionary history that has been occupied by humans and partly because of the small human populations that existed over the relatively brief evolutionary period that they have existed together. Human influence on plants has all been recent, beginning with the use of fire and interference with natural trophic cascades. By far the greatest human impact on plants has occurred in the last few hundred years as human social organization has become vastly more integrated and complex. Though there was a little genetic alteration, by selection over several millennia, and some geographic dispersal of crop plants this was minor compared with contemporary plant breeding, genetic engineering and Cultivated plant globalization of recent times.

Plants, then, are not just ‘useful’ to humans, they have been the source of major human biological and social transformation.

But let’s begin with their utility.

Economic botany, ethnography, and ethnobotany

When this theme is explored in museum exhibitions or discussed in text books, it is usually presented to us through the disciplines of economic botany, ethnography (the systematic study of people and cultures) and ethnobotany (the practical use of plants using the traditional knowledge of local cultures and peoples). The complexities of human-plant interaction are thus simplified and re-framed into a more manageable practical question about plant utility of the form ‘How have different cultures used plants in their daily lives?’

This is, in broad terms, a question about economic botany that can be answered succinctly: firstly, by developing a classification for the many different ways that humans use plants and then by seeing how different cultures have developed their own particular ways of managing these plant uses.

We use plants for food (e.g. grains, roots, and tubers, vegetables, herbs, fruits, nuts, and pulses), food and drink additives (spices, sweeteners, flavourings, and colourings); psychotropic effects (tobacco, tea, coffee, opium, cannabis, beer, mescalin, heroin etc.), as poisons (strychnine); for medicines and drugs (cocaine, echinacea); fibres (cotton, hemp, flax, sisal); dyes (indigo); perfumes and aromas (rose, jasmine, pot-pourri, incense); oils (lavender, ulan, olive), fats (avocado); waxes (beeswax), resins (for varnishes, adhesives, glazes); rubber; wood (as timber, fuel, source of paper); as a source of structural materials; and also for ceremony and decoration.

But economic botany, ethnobotany and related disciplines, which treat plants in a narrow way as commodities and resources indicate only a few of the myriad ways that our world intersects with that of plants. The question is much more complicated than this.

Of these various practical uses it is food that we are inclined to treat as fundamental.
 

Food

Plants provide the food energy that sustains all life. It is plant energy that powered not only bodies, they also facilitated the socio-cultural development that we associate with the settled communities of the Neolithic Agricultural Revolution and which led, eventually, to Bronze Age cities and civilizations. In the modern era it was the concentrated energy of fossil fuels that underpinned the elaboration and globalization of industrial society.

Human bodies take from plants (ultimately) not only food energy sourced from the Sun, but carbohydrate, protein, edible fats and oils, vitamins and minerals.

Globally there are about 3000 known food plants of which about 150 have been
extensively cultivated and traded. In spite of this apparent variety about 90% of the human diet consists of only about 15 species and, of these, only four (wheat, rice, corn and potatoes) make up over 60% of the world’s food supply. We now rarely eat wild food, possibly a few berries, greens and field mushrooms. Regional agriculture evolved based on local plants. In East Asia this was rice. in the Middle East, wheat and barley, and in Central and South America, maize. All staple foods were domesticated in prehistoric times and the full range of cereals, vegetables and fruits are cultigens, that is, they are genetically different from their wild ancestors.

Agriculture and rangeland occupies about 40% of the surface of the Earth (57% of Australia) and food production consumes about 20% of the world’s total plant primary productivity.

The global historical context

Let’s begin with a birds-eye view of the relationship between plants and people by looking at the global scale and the entire course of human history.

All activity is an expression of energy flow. The entire sweep of human history, and the history of all living organisms, would not be possible without the assimilation and expenditure of energy. Life-energy is derived from the energy of the Sun, captured and stored in plant tissues during photosynthesis – and then taken into the body as plant food which is the ultimate life-sustaining fuel for all living creatures in an energy conversion from electromagnetic energy, to chemical energy, to biological energy.

The fact that life could not exist without plants does not appear in history books because it is a ‘given’: but this does not mean that it can be ignored. Plant energy has had a profound influence on the course of human history through two major historical energy-based transformations of human culture, the Neolithic Agricultural Revolution and the Industrial Revolution.

The Neolithic Agricultural Revolution (c. 12,500-2500 BP) took humanity out of wild nature – out of the nomadic hunter-gatherer natural environment of evolutionary adaptation – into artificial or ‘man-made’ farming settlements with cultivated food plants that were the products of human selection. Food energy obtained from wild plants and animal hunting was being replaced by that of domesticated cereals and livestock. Cereal grains were a form of energy that could be stored for year-round use. The surplus plant energy released by agriculture enabled rapid growth in population, division of labour, and an increase in social complexity that facilitated the creation of cities (including designed urban spaces like parks and gardens) and the many cultural activities we associate with civilization. Well-governed urban communities could then take advantage of the technologies of scale by, for example, assembling armies, constructing ocean-going ships, and building up manufacturing industries. A giant step had been taken on the path from nature to culture and from wild environments to cultivated environments as slow biological evolution was supplemented by rapid cultural evolution. All these changes flowed from the surplus energy made available by plant domestication as the human population multiplied from a few million people at the dawn of the post-Ice-Age Agricultural Revolution about 10,000 years ago, to 400 to 500 million in 1650 CE.

The Industrial Revolution (c. 1750-1850) then harnessed the concentrated plant energy in fossil fuels to power technology that would put the Agricultural Revolution into overdrive as the human population soared. It took 200,000 years for the human population to reach 1 billion around 1800: by 1914 the total was about 1.8 billion. The introduction of industrial agriculture was, in effect, a Second Agricultural Revolution creating another dramatic social transformation by releasing people from toil on the land to move from the country into the city: from farm to factory. In 1800 about 3% of the world population lived in cities but by 2017 this had increased to 54.9% (Index Mundi World Demographic Profile 2018). The associated increase in social complexity resulted in technologies and social systems that connected the peoples of the world as never before.

The Industrial Revolution was a period of greatly accelerated cultural evolution characterized by growth and expansion in many factors including: human population, industrialization, urbanization, globalization, democratization, social complexity and knowledge.

The human transition from environments and lifestyles determined by factors in nature, to environments and lifestyles determined by cultural factors, has created a new co-evolutionary relationship between humans and plants. To derive maximum benefit from our association with plants we have, in the course of the Agricultural and Industrial Revolutions, altered our relationship to plants in three major ways: we have devised ever more effective ways of harnessing plant energy, we have modified plant genetics, and we have drastically altered the geographic distribution and species composition of plants over the surface of the Earth.

Human cultural evolution has transformed both plants and their environments. But in so doing we have changed the environments that also shape our own biological and cultural evolution. Humans have domesticated plants but, since plants required the sedentary lifestyle that produced modern civilization humans have, in their turn, been domesticated by plants. Botanic gardens are appropriate institutions to monitor this ongoing plant-human interdependence and co-evolution.

All of human history, and that of all animals, is founded on the availability of plant energy. From this global context of Sun and plant, all else flows …

In summary:

The reciprocal relationship between humans and plants is one of co-evolution. Humans have influenced plants by altering their genetic makeup and reconfiguring the species composition and distribution of plants across the planet. Plants have impacted on humans by influencing human biological and cultural evolution. As the source of life-energy plants have changed human biology and social organization, first through the advent of agriculture, and then through their influence on social organization as the source of fossil fuels that have powered industrial society.

 

Plant classification

A more abstract approach to our relationship with plants might examine the ways that we think about plants – the way we order plants into a meaningful mental experience of the world … what categories do we use when thinking about plants and how do we order these categories into systems of classification?

We think about plants using mental categories that can fit into many different kinds of classification system depending on what we want to achieve. Classification systems in general are ways of organizing knowledge for specific purposes so in the case of plants we might arrange plants differently depending on our purpose- say as foods, medicines, interesting flower colours for a painting we are doing, and so on. Scientific plant classification is therefore just one of many existing and possible plant classification systems for the purpose of determining the was in which plants may be grouped in terms of their elationship to one-another. The article ‘plant classification’ examines the relationship between scientific and other plant classification systems and asks whether the systems of plant classification we use today are the most appropriate ones for present-day circumstances.

For the time-being we can simply list some of the major ways we have experienced, managed and contemplated plants.
 

Plant science

Much is made of the modern-era implementation of observation and experiment during the Scientific Revolution. But both Theophrastus and Aristotle combined logic with close observation to provide the evidence necessary for the empirical generalizations that underpin all science. Historian of botanical science Alan Morton draws attention to the way that agriculture encouraged the circumstances needed to produce writing and that ‘Once invented, writing rapidly became the tool of government and trade and of organised communication and knowledge. Only after the invention and general use of writing could science in the sense of an accepted and accurately transmitted body of knowledge really begin’.

There is another curious aspect of our interest in plants that appears to have a peculiarly western origin, and that is the curiosity about plants that is not based on what we can gain from them (other than the reward of factual information) – that is, it has no basis in self-interest or plant utility. This is the detached interest in plants themselves … for their own sake – a tradition that first appears in the historical record with ancient Greek thought and the botanical text books (lecture notes) of botanist Theophrastus who followed philosopher Aristotle as Head of the Lyceum in ancient Athens. Science studies of plant form and function -their morphology, physiology, biochemistry etc. -and the way that they are related to one-another and their environment. Human interests are usually only incidental in these studies: it is the plants themselves that are the centre of attention. The fascinating history of plant science is discussed in the article plant science history.
 

Plant domestication

From a plant-centred or phytocentric perspective it might seem that human impact has been greatest as a consequence of domestication (although some would argue that it was the plants that domesticated humans). Domestication has three key components: moving them out of natural habitats and thus altering the natural plant geography, changing them physically by selection, breeding, and genetic engineering, in this way, and by cultivating them in various ways.

Cultivated plant geography

Humans have changed, in various ways, the natural distributions of plants. For example: logged forests do not necessarily regenerate to form identical forests if left to themselves; hunting of animals can cause changes in food chains that will affect the composition and distribution of vegetation (see megafauna extinction); the deliberate or accidental burning of vegetation can alter plant geography from that of its pristine state. There is still a keen academic debate about the extent to which the vegetation of Australia seen today is a consequence of deliberate Aboriginal burning regimes in prehistory.

In relatively recent historical times plants have been increasingly collected, propagated and and moved around the planet – as forest trees, agricultural and horticultural crops, and ornamental plants used in parks and gardens. The story of human transport of plants around the world is becoming ever more important as natural vegetation is progressively replaced by human or cultural landscapes . The history of this process is outlined in the article cultivated plant globalization.

Anthropogenic or human-altered plants

Much of the vegetation we experience in our daily lives is comprised of crops of various kinds. These are plants that have been specially selected (sometimes the selection took place so long ago that we no longer know the biological ancestors), subjected to complex breeding programs, or produced by genetic engineering. These are all plant variants that are genetically different from their wild relations. These human-altered or anthropogenic plants are referred to technically as cultigens and they are discussed in the article anthropogenic plants.

Major historical transitions
Key transitions in the human relationship to plants delve into origins. Origins fascinate us, whether it be the universe, the origin of life, the dawn of consciousness and language, or our own ancestry. The origins of key features or transitions in human life satisfy intellectual curiosity but they also throw into relief the way that small changes at the beginning of a developmental process can have momentous long-term impacts. Where there is flexibility in the timing of origins then they can impact significantly on the timing and outcomes of other historical processes. In the relationship between plants and people the greatest revolutionary transition was from hunter-gatherer to plant cultivator. This humble beginning would then spawn the great cultivated plant traditions of agriculture, horticulture and forestry including plant domestication as the human manipulation of plant genetics. In the modern era we see the advent of biological globalization, the human disperal of plants across the planet.

human nature
Another way of looking at our relationship to plants is by distinguishing between those aspects of our relationship to plants that are universal to our human nature, that is, common to all cultures, or innate (see Plants make sense) and how these innate responses have been integrated into cultural evolution.

Plant-human coevolution
The biological relationship between humans and plants is a very close one, beginning with the oxygen in the atmosphere on which we all – plants, animals and humans – depend for our survival. Oxygen was placed in the atmosphere by plants. Our body structure, sight, digestion and other factors have been determined at least in part by our association with plants, they are part of the process of the coevolution of humans and plants that is discussed in the article Plants make sense. We speak of the domestication of plants it was agriculture that confined humans to the cities that helped define civilization and modern life: in this sense plants domesticated humans.

Cultivated plant geography
But then there is the way that economic botany has impacted world vegetation at a planetary scale. This is cultivated plant floristics – the study of the composition and distribution of cultivated plants on planet Earth and its change over time. Here several key events are discussed some detail: the impact that occurred in prehistory through fire and other forms of vegetation disturbance; the origin and development of plant cultivation and its appropriation of land specifically for this purpose; the domestication of plants by genetic manipulation – their selection, breeding, and genetic modification; the large-scale redistribution of plants across the planet; and the human-managed integration of economic botany with other human and planetary processes for the benefit of both humans and the community of life. The latter topic is addressed under the heading ‘Sustainability‘.

Relationship to human well-being
In the 21st century we have taken a much more inclusive, generalized view of plant utility viewed through an economic lens with nature as ‘natural capital’ and plants as a human service. For example, one lesson we learn from evolutionary biology is that, so far as we can tell, all life evolved from a single common ancestor. Part of our human genetic make-up was inherited from organisms that that later diverged into the plant and animal kingdoms. Animals and plants are both classified as eukaryotes (a category that includes fungi and slime moulds with membrane bound organelles) and the split between the two kingdoms is believed to have occurred about 1.6 billion years ago (109). This means that all living things are related and that we can rightly speak of the ‘community of life’ viewing the biosphere as a globally integrated ecosystem.

This gives us a general context or framework of ideas that can assist us in the task of global management. The key idea is that of Ecosystem Services[1] which is convenient shorthand for the many ways in which humans benefit from nature. The overall goal is to provide the well-being that allows each individual to achieve what they value doing and being by maximising freedom of choice and action. There are several basic constituents of well-being: security (as personal safety, and maximum protection from political and natural disasters); access to basic material resources (jobs, food and goods, shelter); health (access to clean air and water, and medical attention); and good social relations through mutual respect and support. From this perspective, if we are to maximise human well-being then we need to know how Ecosystem Services contribute to the constituents of well-being. The Millennium Ecosystem Report[1] proposes four ways in which this can done: by provisioning (e.g. food or fresh water, materials), regulating (e.g. climate, flood, disease etc.), supporting (e.g. nutrient cycling, soil formation, primary production, pollinators), and finally cultural (aesthetic, spiritual, educational, recreational).

What about social and historical change – big change like the Neolithic Revolution which was founded on the domestication of plants … but also landscape change in general? There is the story of alien invasive plants introduced by humans and swamping native plant populations? And it seems to be ignoring contemporary science topics like plant biotechnology, genetic engineering or even botanical art. What about the fact that

Our modern world is firmly grounded in its science and technology. But how did our scientific interest in plants originate? Although our distant ancestors would inevitably have been using elements of the scientific method as they experimented with different foods and materials, accepting those that ‘worked’ and rejecting those that did not, but the written record indicates that practical concerns were centred strongly, not on food, but on the medicinal use of plants. It seems we must look to the intellectual melting pot that was Athens in the third century a vibrant city at the centre of Mediterranean including visiting merchants and cognoscenti of Minoa, Mesopotamia and Egypt at a time when Greece was at the zenith of its colonisation of the Mediterranean. At the centre of this movement was the Lyceum, an institutional centre similar to a university training the leaders of the future. Famous philosopher Aristotle was succeeded by Theophrastus as its Head and it was Theophrastus’s lecture notes, his Enquiry into Plants, that mark the strating point for botany and plant science. His work marked a time when thinking changed from being human-centred (anthropocentric), examining them in terms of their physical impact on human life, to a more to a dispassionate and genuine curiosity about the plants themselves beginning documentation on topics like plant geography, morphology, physiology, nutrition, growth, reproduction and their similarities to one-another. Theophrastus was asking questions about plant form and function that have occupied much of subsequent plant science at a time in history when other Greek academics were expressing rudimentary ideas about organic evolution. It was the dawn of plant science but a methodology and agenda that returned to former interests, the monastic concerns about the medicinal use of plants which consumed the study of plants for about 1,200 years before the emergence of physic gardens and the advent of botanic gardens at the time of the Renaissance. One of its major consequences was scientific classification based on similarities and differences in physical characteristics, rather than the practical categories (fruit/vegetable; medicine/drug etc.) used in folk taxonomies. It was a scientific and intellectual schism that has not always been comfortable, bubbling to the social surface in various forms: the Resistance of Romanticism to the reason of the Enlightenment.

Perhaps at the other end of the spectrum was the world of the arts and imagination, not only art itself, but plants and their relation to sentiment, feeling and association.

we also use them in religious ceremonies, social rituals and ornament (body decoration, floristry, ornamental horticulture).

It soon becomes evident that the link between plants and people is so pervasive that when we try to isolate particular topics – say history, trade, food or botany – the topics seem to merge into one-another. Like the concept of sustainability the connection between plants and people is so deeply ingrained in everything we do that in attempting to categorise it the question, in effect, is asking for the categories through which we perceive our lives as a whole, that is, human activity in space (social development) and time (history) encompassing both the physical world and the world of ideas.

As a way of coming to grips with the magnitude of the topic I have prepared two diagrams, one based mainly on the world of ideas and the other based more on human affairs. The diagram unites two pairs of often contrasting topics, the first pair being art and science, and the second pair nature and culture. The second diagram is a pictorial representation of the way future human sustainability is to be assured through the cooperative intersection of three key domains in which humans operate – the environmental, social and economic.

 

People
History may be presented as a parade of influential and powerful people in particular spheres of interest, though a narrow perspective on history, this can provide useful insights? Any historical list will be contentious but here is my selection, in chronological order, with notes on their contribution. I have compiled a more extensive but less detailed list of Plant People in Australia.

There are various aspects of human culture, of human sentiment and ideas, that are concerned specifically with plants. We can include here the part that plants have played in religion (see Christianity and nature) and folklore (see Plant folklore 1 ), Plant folklore 2 and our current attitudes, the way we relate to and perceive the natural world (see Evironmental ethics, and Sustainability).

Introduction
Plants are so much a part of our everyday lives that is difficult to know how to start explaining this relationship. Perhaps the first approach is to summarise the many ways in which we use plants – say as food, timber and for medicines – to consider them in terms of their utility. On closer inspection this might seem a rather narrow perspective. Clearly plants have played a major role in economics and social change by playing a major role in global trade. We might ask how that role has changed over time and create a chronological or historical account of that influence for a particular region or situation. But then our interest in this topic might have been stirred by the scientific or cultural function of plants, their importance in horticulture, botany, agriculture and forestry or their role in landscapes or botanical art. Maybe our interest has been sparked by a concern for the environment and an acknowledgement of the mystery, beauty and complexity of the natural world? No matter from what angle we view the plant kingdom we will also be looking to the future and speculating on how our relationship will change in the future and ways in which our relationship with plants and the planet can be more effectively managed.

For convenience these many connections have been summarised on this web site under four headings:

  • Utility – Plants as a human resource
  • History – Mutual interaction of plants and humans over time
  • The place of plants in Art, Science & Culture
  • Sustainability – Plants and the future

 

Changing nature
The technical term for a plant that has been deliberately altered or selected by humans is ‘cultigen’. [1]Spencer, R.D. and Cross, R.G. 2007.The International Code of Botanical Nomenclature (ICBN), the International Code of Nomenclature for Cultivated Plants (ICNCP), and the Cultigen.Taxon 56(3):938-940 These anthropogenic plants have arisen by a special kind of human-based natural selection called artificial selection. Chapter 1 of Darwin’s Origin of Species (1859) was titled ‘Variation under domestication’ and it was clearly Darwin’s observations on human breeding of greyhounds, horses, pigeons, vegetables and the like that had stimulated his thinking on variation and selection in general. Cultigens, human-produced plant variation, are of several different kinds. The first cultigens were the crops selected by our Neolithic ancestors, perhaps unconsciously as, year after year, they collected seed from the highest yielding plants thus gradually changing the genetic make-up of the plants from that of their wild ancestors. Then there are the occasional ‘sports’ or aberrations that can be reproduced – perhaps some variegated foliage that can be propagated to retain the variegation. One favoured way of gettingthe features of a plant that you want is by grafting. However, the most obvious cultigens are plants that are the result of deliberate breeding programs that produce popular ornamental plants like large and colourful roses or high yielding crops. In recent times there are the transgenic plants produced by genetic engineering: these are not produced by selective breeding, but the result of the deliberate manipulation of DNA itself. To this list can be added plants with special desirable characteristics that have been selected from the wild. These are have not beenaltered genetically but might have acharacter, like an unusual flower colour, that has commercial value.

Educators now have the difficult decision about which parts of the plant picture are to be passed on. At the time of the Greeks with little detailed knowledge or, ut seems for that matter, interest in plants themselves there was the rich study area of botany as structure (morphology and classification), function (physiology) and reproduction (reproductive biology) with the admixture of the ‘applied’ agriculture and forestry. The idea of studying ‘plants for themselves’ rather than their uses served apurpose for two millennia until the reality that plants do not exist in isolation but in interaction with the environment came crashing in with the proliferation of new disciplines in the 19th century: evolution, biogeography, and ecology. Drilling into the molecular composition of matter continued with genetics leading to the discovery of the ‘genetic code’ which now provides the thrust of modern research, jobs, and therefore vocational training through molecular systematics, genomics and informatics. Through all this there is value in maintaining perspective through a grounding in macro-level big-picture Big History (with its cautions of global level effects of human activity) and micro-level analysis that extends our understanding of life’s most intricate secrets while feeding new technologies.

Valuing plants
Plants, which comprise so mush of our lives – what we look at, the objects of daily life that we use, what we eat and so on, receive very little press. This might be in part due to their lack of motility and brains which for animals like us makes them secondary phenomena. Nevertheless this is a phenomenon that has drawn some attention as ‘plant blindness‘.[3][4]

The world’s first scientific biologist, Aristotle noted the time and scientific attention given to the heavens. The ancient Greeks had inherited elaborate records concerning the stars and their movements. Astronomy had been a major preoccupation of learned Sumerians and Babylonians and this tradition has continued to the present day. Aristotle appealed for some attention to be given to the wondrous and humble world of organisms that was all around us but times have hardly changed. Physics is still given pride of place in the sciences as a matter of fact mathematical hard science done mostly by men. Biology is a soft science done by women and those who could not cope with the intellectual challenge of universal laws and mathematics. Only now are we beginning to challenge the idea that reality is itself about ‘fundamental’ objects like molecules, atoms, quarks, and quantum mechanics rather than objects like animals, plants, and human beings.

The eighteenth century saw the rise of Botanophilia, a passion for plants, botany and horticulture, that swept the western world. This was a period of plant ascendancy perhaps not exceeded since our blatant dependence on plants as hunter-gatherers and the first agrarians. As food sources become secure we concern ourselves with them less. Perhaps today our day-to-day ignorance of plants has never been greater. We only know the names of common vegetables and garden plants and perhaps just a few plants growing in the wild. We have little idea of where the vegetables, fruits, and nuts we buy at the Supermarket were grown since they are now sourced based on global economics. And we know even less about how they are cultivated and what they look like as mature plants. Up to the Industrial Revolution almost everyone was employed on the land, today the number of land-workers is in the region of 2%.

All this has influenced our outlook on what we see as interesting and important in our lives: physics is more important than plant science, animals are more interesting than plants. Food security is taken for granted and plants now serve a role as ornamental and culinary accessories . The daily greeting of workers on the pyramids of ancient Egypt was ‘Bread and Beer mate”: they knew what was crucial in life. Today because, for most of us, th basics in life are ‘covered’, their perceptual significance recedes into the background while their reality remains.

Major Historical Events
Plants have had a major impact on humanity in seven major ways, three of these being major world-changing historical events. Inevitably all seven impacts are insinuated into many articles on this web site but are briefly summarised below:

1. The great oxygenation event
About 3.5 billion years ago oxygen was first added to the Earth’s atmosphere by photosynthetic cyanobacteria as a waste product. At first rapidly absorbed by organic compounds and dissolved iron it produced layers of iron oxide on the ocean floor until about 2.3 billion years ago excess free oxygen began to accumulate in the atmosphere during the Great Oxygenation Event

2. Co-evolution
Humans co-evolved with plants this strongly affecting our senses of taste, smell, digestive system and dentition, our emotional response to our surroundings, and possibly the initiating factor for the fact that we are bipedal and have colour vision. This is discussed further in the article Plants make sense

3. The Neolithic Revolution
The cultivation of crops during the Neolithic Revolution created the surplus wealth that made the advent of cities and civilization possible. This was without doubt one of the most momentous social transitions in the history of humanity and it hardly seems too outlandish to suggest that this was not a consequence of the domestication of plants by humans but exactly the reverse. See article on the Neolithic Revolution and related articles.

4. Creating a global economy
The search for spices in the fifteenth and sixteenth centuries initiated the Age of Discovery and colonial expansion that transformed the global economy and world in a major phase of globalization that included the wide dispersal of temperate and tropical crops and adventive plants across the globe. See, for example, articles related to the Silk Road and Spice Trade and related articles.

A major legacy of this era of empire and trade was the modification of diet (especially in the Western world) as food plants formerly restricted to particular regions were now dispersed world-wide. Europeans exported their farming practices associated with the cereals wheat, oats, barley, and rye, transforming the landscapes of the Neo-Europes and imports came from southern North America (cotton), South America (maize from Mexico, potatoes, chillies, pineapples, and tomatoes from the Andes, vanilla, tobacco, and cocoa from Central America, Rubber from Bolivia and Brazil), China (rice, tea, silk), South and SE Asia (bananas, sugarcane), Polynesia (coconuts), tropical Africa (coffee). Unsually Australia has contributed no major food plants to world cuisine, the macadamia nut being the only commercialised food crop. There were also the plants associated with domesticated animals and the timbers and other plants useed in the construction of the rapidly improvong ships used for transportation.

5. Powering the Industrial Revolution
The concentrated energy contained in the coal, oil, and gas that made the Industrial Revolution possible is derived from fossilized ancient plants. We may think of spices as symbolising a time when plants were highly sought-after products that provided the incentive for world trade, inspiring improvements in technology and an Age of European Discovery. Though today it is mostly oil that powers the world economy no less than seven plants feature in today’s top ten traded commodities – in order of value: crude oil, coffee, natural gas, wheat, cotton, corn, sugar (others are gold, silver, copper).

6. Provision of drink
The six most influential drinks in human history have all been plant-based: beer, wine, spirits, tea, coffee, and cola.

7. Provision of food – energy capture/population size/social organization
Globally there are about 3000 known food plants of which about 150 have been extensively cultivated and traded. Today about 90% of the human diet consists of about 15 species. According to the United Nations Food and Agriculture Organization just twelve crops provide 75 percent of the world’s food. Three of these crops, rice, maize, wheat, and potatoes contribute over 60 percent of the protein and calories obtained by humans from plants. We now rarely eat wild food, possibly a few berries, greens, and field mushrooms. Regional agriculture evolved based largely on local cereal plants so in East Asia this was rice, in the Midle East wheat and barley, in Central and South America maize. All staple foods were domesticated in prehistoric times and the full range of cereals, vegetables, and fruits are genetically different from their wild ancestors. Our basic need for plant crops is the single most environmentally demanding aspect of our lives with, above all, its demand for land, but also water (70-95% of our water use), energy, and infrastructure.

Since the beginning of the 20th century, some 75 percent of plant genetic diversity has been lost. Researching indigenous crops may in part address potential threats to food security and stall the increasing loss of biodiversity. Some traditional plant varieties can help improve nutrition and health, improve local economies, create resilience to climate change, revitalize agricultural biodiversity, and help preserve tradition and culture.Food security is a potential global sustainability issue so organisations like the World Vegetable Center , the Vegetable Genetic Resources System, and Slow Food International’s Ark of Taste are making a catalogue of indigenous species of fruits and vegetables around the world while Bioversity International, a research organization in Italy, is developing policy to safeguard biodiversity of trees and in agriculture to maintain sustainable global food and nutrition security.

8. Energy capture & social organization
Foragers
The close relation between mode of energy capture and social organization over the long term begins with foragers as hunter-gatherer societies in nature capturing food energy from wild animals and plants generally in mobile bands of no more than 20- 100 people, the men hunting animals and the women collecting plant foods.

Farmers
Then beginning about 12,000 BP the formation of settled agrarian farmer societies with food-energy captured from cultivated plants and domesticated animals, most people occupied with food production, storage and distribution but sufficient food available (as wealth or affluence) to permit the increase in population, division of labour, urbanization into populations of 1000s and hierarchical cultural complexity that collectively take advantage of the benefits of scale (monumental architecture, ocean-going ships, armies, communal technology) with wider networks of communication, improved technology, and accumulation of beneficial information.

Fossil fuel industrial agriculture
All these ‘growth’ factors were accelerated with the use of the concentrated energy of the sun stored in dead plants as fossil fuels combined into modern industrial agriculture. Industrial agriculture responded to the Great Acceleration of population from 2 billion in 1930 to 7 billion in 2015 with the further addition of agrochemicals and biotechnology.

9. Three agricultural revolutions & population growth
The First Agricultural Revolution was the Neolithic Revolution of settled communities living with domesticated animals and plants. This arose independently in about five major areas across the world between about 12000 BP and 4000 BP at a time when the world population possibly ranged around 1 to 10 million.

The Second Agricultural Revolution took advantage of the concentrated energy of fossil fuels, slowly introducing industrial agriculture and bringing the world population from 350 million in 1500 to about 1 billion in 1800 then, as industrialization spread out of Europe across the world, up to 2 billion in 1930.

A Third Agricultural Revolution was needed to meet the demands of the ‘Great Acceleration’ when the world population exploded from 2 billion in 1930 to 7 billion in 2015. This began as the Green Revolution of the 1950s and ‘60s which increased agricultural output by using synthetic chemicals (fertilizers, weedicides, pesticides) and increased irrigation to boost the growth of high-yielding newly-bred cereals like dwarf wheat and rice. It was a revolution that combined modern machinery, large farms, and the bioengineering of crops that needed a high input of agrochemicals and water. This lifted much of the developing world out of poverty but there was an environmental cost. The Green Revolution was built, in part, on the genetics that had matured in the 1930s and which was supplemented, after 1980, by the genetically-engineered crops made possible by the deciphering of the genetic code in the 1950s.

10. Provision of materials
We use plants as food; food and drink additives; psychoactive plants; poisons; as medicines and drugs; fibres; dyes; perfumes and aromas; oils, fats, waxes; resins; rubber; wood and timber for fuel and paper; for structural materials, decoration, and ceremony.

 

Key points

 

  • Plants provide the energy and oxygen that sustains all life; they have influenced the biological evolution of our bodies notably our senses of taste and smell, our digestion and dentition, and our bipedal gait and colour vision; the advent of agriculture created the surplus wealth that made civilization possible; they provide us with the essential materials of our daily existence.
    • Our mode of plant energy capture used for food production has also greatly influenced our cultural evolution, the kinds of social organization that have arisen over time.
      • About 3.5 billion years ago oxygen was first added to the Earth’s atmosphere by photosynthetic cyanobacteria as a waste product. At first rapidly absorbed by organic compounds and dissolved iron it produced layers of iron oxide on the ocean floor until about 2.3 billion years ago excess free oxygen began to accumulate in the atmosphere during the Great Oxygenation Event
        • Plants provide the energy (obtained from the Sun) and oxygen that sustains all life: they are the primary producers at the base of the food chain

          • The cultivation of crops during the Neolithic Revolution created the surplus (energy) wealth that made the advent of cities and civilization possible
            • The search for spices in the Age of Discovery accelerated the formation of a global economy that was later given further momentum by the Industrial Revolution that was fuelled by the concentrated fossil plant energy contained in coal, oil, and gas; plants have been the main ingredient of all the worlds major liquid refreshments
              • We use plants as food; food and drink additives; psychoactive plants; poisons; as medicines and drugs; fibres; dyes; perfumes and aromas; oils, fats, waxes; resins; rubber; wood fuels as timber, coal, oil, gas; paper; for structural materials, decoration, and ceremony. They featured I strong traditions of folklore
                • The search for spices in the 15th and 16th centuries initiated the Age of Discovery and colonial expansion that transformed the global economy and world in a major phase of globalization that included the wide dispersal of temperate and tropical crops and adventive plants across the globe
                  • The concentrated energy contained in the coal, oil, and gas (fossilized ancient plants) that made the Industrial Revolution possible, stimulating a global fossil-fuel-driven global market economy
                    • The six most influential drinks in human history have all been plant-based: beer, wine, spirits, tea, coffee, and cola
                      • Plants underpin the global economy. Of today’s top ten traded commodities seven are plant-based – in order of value: crude oil, coffee, natural gas, wheat, cotton, corn, sugar
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