Humans: past, present and future
Humans are one species among the millions which exist or have existed since the beginning of life almost 4 billion years ago. All such species have lived on the wafer-thin surface of one small planet as it turns in space. The biologist E. O. Wilson once wrote of a hypothetical journey from the centre of the Earth:
"For the first twelve weeks you travel through furnace-hot rock and magma devoid of life. Three minutes to the surface, five hundred meters to go, you encounter the first organisms, bacteria feeding on nutrients that have filtered into the deep water-bearing strata. You breach the surface and for ten seconds glimpse a dazzling burst of life, tens of thousands of species of micro-organisms, plants and animals within a horizontal line of sight. Half a minute later almost all are gone. Two hours later only the faintest traces remain consisting largely of people in airliners who are filled in turn with bacteria."
I begin in this way to underline the limited and precarious character of all life on Earth, including our own, in its physical environment. We can attempt to distinguish the geosphere from the biosphere, but neither can be fully understood except as parts of a single integrated system.
That system has always been on the edge, and always will be. It is just that the shortness of our lives and the narrowness of our perspective on Earth history mean that we are mostly unaware of change, and until now scarcely notice the pressures on the environment. The last couple of centuries have seen an extraordinary stretching of our understanding of space and time. We can now look beyond the solar system, beyond our galaxy, beyond billions of other galaxies, back to the big bang which initiated the universe we know.
As for time, we can look beyond the last thousand years, beyond the beginnings of civilization, beyond the patch of warmth in the last 12,000 years, beyond the many spasms of the ice ages, beyond the multicellular, eukaryotic organisms, and further back to the origins of life itself.
During these almost unimaginable stretches of time, there have been big hits from space, the changing relationship between the Earth and the Sun, the slow movement of tectonic plates on the Earth's surface, the rise and fall of sea levels, major volcanic eruptions, and not least the influence of life itself. The tightly linked living organisms on the Earth's surface work as a single self-regulating system, tending to create and maintain the environment most favourable to them.
Over time the system has tipped many ways, sometimes violently, to the detriment of this or that group of organisms. There have always been correctives. Yet today one small animal species - our own - is tipping the system in ways that cannot be foreseen.
That species is very new. No-one was around to record the evolution of the first human-like creatures from ape like ancestors in Africa some four million years ago. They left the trees for the savannah, became relatively hairless, and learned to walk upright on two legs, with consequences for the physiology of their growing brains. By at least half a million years ago, they had split into a variety of related strains, and spread far beyond Africa. One of their offshoots may still have been living on the Indonesian island of Flores as recently as 12,000 years ago (a mere blink in geological time). Our own lot can first be identified between 200,000 and 150,000 years ago.
Through analysis of fossils and work on current humans, we have been able to trace our genealogy back to so-called mitochondrial Eve (the female line) some 150,000 years ago, and Y chromosome Adam (the male line) less certainly between 90,000 and 60,000 years ago. It may seem amazing but all living humans may be descended from both with of course millions of mixtures on the way. Other branches of humans, including our cousins the Neanderthalers, are now extinct.
It seems likely that there was some sort of crisis in human history which drastically reduced numbers and eliminated some of the lines of descent. Among the possibilities are abrupt climate change following the violent eruption of Mount Toba in Indonesia some 73,000 years ago, which initiated a severe cooling of the Earth within the Pleistocene ice ages.
We know from recent history what big effects volcanic eruptions can have (Mount Laki in Iceland in 1783, Tambora in 1815 and Krakatoa in 1883), and Toba was a real monster among them. But there are other possibilities: some major epidemic like the Plague of Justinian in 540 AD, or the Black Death which devastated populations worldwide in the 14th century; or even a hit from space (if the object which devastated part of Siberia as recently as 1908 had hit London, there would have been nothing left within the M25 ring road).
The survivors of this major crisis, whatever and whenever it was, would have had many genes in common, and thereby influenced the character of subsequent generations. All modern humans are fairly close cousins. There are more genetic differences between Africans than there are between Africans and other humans, thereby indicating our African origins.
A question which still arouses much controversy is when and why humans developed the attributes we all now take for granted: language, music, symbolic and interconnected thought, art in its many forms, including jewellery, advanced technical skills, and certain behaviour patterns, including respect for the dead. Did this grow gradually out of development of tools for hunting, fishing and shelter, sexual competitiveness, the management of community relationships, or something else? Or was it the product of some genetic mutation which greatly advantaged some individuals and their descendants at the expense of others?
Evidence for humans with modern attributes, as seen for example in cave paintings, goes back some 40,000 years in Europe, but shell and coral beads and other artifacts, including pigment, have been found in South Africa and dated from around 75,000 years ago. Perhaps the answer is both factors. Whenever the change took place, the extraordinary development of human brain power, which has produced ourselves, occupies much less than 1 percent of all human history.
Over the last 40,000 years the human impact on the Earth has slowly and then rapidly increased. Hunter gatherers fitted easily, although sometimes uncomfortably, into the ecosystems of cold and warm periods of the Pleistocene. People migrated in response to changing conditions. But farming with land clearance between 10,000 and 8,000 years ago changed everything. It may even have changed the climate and, by affecting emissions of carbon dioxide and methane into the atmosphere, halted a return to colder conditions.
With a vast increase in human population came towns and eventually cities. Tribal communities evolved into complex hierarchical societies. Before the industrial revolution some 250 years, the effects of human activity were local, or at most regional, rather than global. Now the impact is indeed global.
The idea may be hard to accept, but in its long history with all its variations the Earth has never been in this situation before. In the words of the title of a recent book on environmental history, we confront Something New Under the Sun. These points were well brought out in a remarkable Declaration published by some 1500 scientists from the four great global research programmes at Amsterdam in July 2001. They stated squarely that:
"Human activities have the potential to switch the Earth's System to alternative modes of operation that may prove irreversible and less hospitable to humans and other life ...
"The accelerating human transformation of the Earth's environment is not sustainable. Therefore the business-as-usual way of dealing with the Earth's System is not an option. It has to be replaced - as soon as possible - by deliberate strategies of management that sustain the Earth's environment while meeting social and economic development objectives."
The problem is almost on a geological scale. No wonder the Nobel prize winner Paul Crutzen with his colleague Eugene Stoermer should have named the current epoch the Anthropocene, in succession to the Holocene epoch of the last 10,000 years.
There are six main factors which have driven this transformation. Briefly they arise from human population increase; degradation of land, consumption of resources and accumulation of wastes; water pollution and supply; climate change in its many aspects and impacts; energy production and use; and destruction of biodiversity.
Of these factors population issues are often ignored as somehow too embarrassing or mixed up with religion and the ideology of development; most people are broadly aware of land resource and waste problems, although far from accepting the remedies necessary; water issues, both fresh and salt, have had a lot of publicity, and already affect most people on this planet; climate change with all its implications for atmospheric chemistry is also broadly understood, apart from by those who do not want to understand it; how we generate energy while fossil fuel resources diminish and demand increases is another conundrum; but damage to the diversity of life on which our species critically depends has somehow escaped most public attention. Yet here human destructiveness has been most evident over the last 10,000 years. Current rates of extinction could in the long run be the most important of all these factors for human welfare. All are interlinked, and all represent pressure on the natural environment.
There is now a seventh factor recent in human experience. So far the effects remain mostly to be seen. They arise from the introduction of new technologies. Damage to the ozone layer, which protects ecosystems from harmful ultraviolet radiation from the Sun, was the first to receive major public attention. The eventual result was to establish international agreements to ban the manufacture and use of chlorofluorocarbons.
But this may only be the beginning. In a recent book by the Astronomer Royal and President of the Royal Society, Sir Martin, now Lord Rees explored the dangers arising from human inventiveness, folly, wickedness and sheer inadvertence. The ramifications of information technology, nano-technology and nuclear experimentation and the rest have still to be understood and explored. His conclusion was to give our civilization only a 50 percent chance of survival beyond the end of this century.
James Lovelock recently gave a comparable warning. He wrote:
"We have grown in number to the point where our presence is perceptibly disabling the planet like a disease. As in human diseases there are four possible outcomes: destruction of the invading disease organisms; chronic infection; destruction of the host; or symbiosis - a lasting relationship of mutual benefit to the host and the invader."
What then are we to expect? Are we capable of establishing a lasting relationship of mutual benefit to the living Earth and those of its unruly inhabitants who are ourselves? How are we to recognize that the last 200 years or so have been a bonanza of inventiveness, exploitation and consumption which may not continue?
All successful species, whether bivalves, beetles or humans, multiply until they come up against the environmental stops, reach some accommodation with the rest of the environment, and willy-nilly restore some balance. In the long history of the Earth, we are the only species capable of recognizing that the problems outlined above exist, and that sooner rather than later something has to be done about them.
In fact most of the solutions to the problems we are causing are well known. Take population increase. The overall rate is still rising but in several parts of the world, including our own, it is levelling off. The main factors are improvement in the status of women, better provision for old age, wider availability of contraceptive devices, lower child mortality, and better education, especially for girls and young women.
Even so, according to the first UN Millennium Ecosystem Assessment report, if current trends are anything to judge by, in 2050 we may well have a population of 3 billion more people, bringing the total to between 8 and 9 billion. Yet when I was born, the population was around 2 billion. If this rate of increase were in swallows, spiders or elephants, we should be scared silly. But because it is ourselves, we accept it as almost normal.
Take degradation of land and water. We know how to look after them both if we try. We do not have to exhaust top soils, watch them erode into the sea, rely upon artificial aids to nature, eliminate the forests with their rich variety of ecological functions, or pollute the water, fresh and salt. We already accept the need for conservation and for better understanding of the complexity of living systems. Some at least are aware of the risks in high technology, and are trying to cope with them.
We do not have to consume often irreplaceable resources at the present epic rate. A Chinese friend of mine has calculated that during the last century humans consumed 142 billion tons of petroleum and 265 billion tons of mineral coal. As someone recently remarked, it took around 200 million years to lay down the coal, oil and gas on which our society depends. We are consuming them over a period of around 200 years. Thus each single year we consume a million years of fossil fuel deposit. This is profoundly affecting the chemistry of the atmosphere which now has more carbon dioxide in it than over the last 650,000 years. Again we do not have to do it. There is never going to be a shortage of energy. The only question is how we generate it, and there are many alternatives.
Nor do we have to condone the widening division of human society between rich and poor. Understandably people in poor countries want to follow the industrial countries in exploiting natural resources to the full, raising living standards, and participating in the consumer culture. Yet in many ways this is an impossibility.
Over the last few years stockmarket indices may have arisen, but the world's natural wealth, measured by the health of its terrestrial, freshwater and marine species fell by no less than 40 percent between 1970 and 2000. In 2001 humanity's ecological footprint exceeded the Earth's biological capacity by about 20 percent. This underlines the need to avoid the misleading characterization, based on a false biological analogy, between "underdeveloped", "developing" and "developed" countries.
This division between rich and poor is a prime and a growing source of insecurity for all. At present about 20 percent of the world's people consume between 70 percent and 80 percent of its resources. The division is not only between countries but also inside them. Such countries have almost totally different economies working within them.
For example new elites in India and China are now acquiring similar purchasing power to the middle classes in industrial countries. Increased meat consumption by middle class Chinese already threatens to perturb world grain markets as more cereal is needed for cattle feed. The contrast is increasingly between small numbers of globalized rich and large numbers of localized poor.
Some economists suggest that market forces will eventually bring their version of development to all. The trends suggest the opposite. Living conditions have certainly improved for many people over the last 250 years, and most people are living longer. But it is hard to see how this can continue. Our ability to respond to change is constantly being diminished. More people than ever are fleeing poverty, water and food shortages, health problems, storms, floods and droughts, and by most reckonings the number of environmental refugees will greatly increase. In a world where the internet lets knowledge travel ever wider, ever faster, inequalities in living conditions are becoming more generally known and felt.
This huge array of different but closely connected problems is so intimidating that even when solutions to them are known or knowable, few want to confront them whether singly or together. We all suffer from the disease of what has been called conceptual sclerosis. Little is more difficult than learning to think differently, above all when the problems go to the roots of the conventional wisdom. Most difficult of all, they relate directly to our current value system. Economies is one aspect of it.
Any change in a system that gives primacy to market forces, exploitation of resources and ever rising consumption will be uncommonly painful. Unqualified economic growth is an obsession with some economists and politicians who see growth as something without natural limits. Many want to attach monetary value to almost everything. But how can anyone give a monetary value to pollution of the atmosphere, acidification of the oceans, loss of a species, or supply of such natural services as microbial disposal of wastes?
Of course some rule-of-thumb method of assessing and comparing values would indeed be useful, not least in giving comfort to economists and more plausibility to their models. But somehow we have to bring in the factor of costs. As has been well said, markets are superb at setting prices but incapable of recognizing costs. It has also been well said that the economy is a wholly owned subsidiary of the environment. Governments have a particular responsibility to determine what is in the public interest, and to use fiscal instruments to promote it.
This is not the time for setting out a kind of action programme for governments, universities, communities, companies, individuals or anyone else. That would be for another occasion.
I want now to turn to the future of our species in a world which is changing under human impulsion before our eyes. Bear in mind that nearly all forecasting turns out to be wrong. We do well to expect the unexpected. Who would have forecast the rise of information technology, and its enormous effects, even 15 years ago? Instead I prefer to play for safety and peer further ahead, perhaps 200 years, and from this vantage point look backwards.
By 2200 there will probably have been some sudden disruptions, whether volcanic explosions, earthquakes, impacts of extraterrestrial objects, or even destructive wars using unimaginably horrible weapons. Worldwide the relationship between land and sea will change, and maps will be redrawn. The politics of the world will be different with new hubs of power, wealth and culture. Ecosystems will be drastically changed. Already the rate of extinction of other species can be compared to those of the five great extinctions in the geological history of the last 500 million years. Human health will be affected by these changing conditions. There is a powerful synergy between pathogen transmission and environmental change. Old diseases will return, new ones will arise and spread.
How our successors, if there be such, will react to these new circumstances is anyone's guess. They are likely to be living in a more globalized world of rapid communication. Units of information - or memes - will pass almost instantaneously between countries, communties and individuals, and for the first time there will be something like a single human civilization.
Human numbers in cities or elsewhere will almost certainly be reduced, and their distribution will almost certainly be very different. It has been suggested that an optimum population for the Earth in terms of its resources would be nearer to 2.5 billion rather than - as now - over 6 billion. Communities are likely to be more dispersed without the daily tides of people flowing in and out of cities for work. Transport systems will be very difficult. Archaeologists of the future may even wonder what all those roads were for.
Then there are other developments in information technology. Here come the most radical possibilities of all. So far evolution has proceeded by natural selection in its various aspects. In the last few thousand years humans have played games with it through artificial breeding of organisms - from cereals to cows and dogs - to suit their purposes. Such processes were always slow. But now through lateral gene transfer, humans may rapidly be producing new varieties, sub species and even new species. This could apply to humans themselves. H. G. Wells invented Eloi and Morlocks (those up above and those down below). At the time, more than a century ago, it seemed an amusing fantasy. No longer. Redesigning humans has become a real possibility. It is worth remembering how vulnerable even the Eloi were.
Other applications of information technology range far beyond enumeration. Already chips have been inserted into humans for a variety of purposes. On the one hand humans may thereby be liberated from many current drudgeries. Soon houses will may be able to clean themselves, meals could appear on demand, cars will drive under remote instruction, and evolution of desirable characteristics could even be automated. All this seems unimaginable when so many still have to trudge miles to collect fuel wood and water.
On the other hand humans could well become dangerously vulnerable to technological breakdown, and thereby lose an essential measure of self-sufficiency. Already dependence on computers to run our complex systems, and reliance on electronic information transfer, are having alarming effects. Here industrial countries are far more vulnerable than others. Just look at the effects of single and temporary power cuts. More than ever individuals feel out of control of even the most elementary aspects of their lives.
The implications for governance reach equally wide. In the words of a recent book, we have to recognize that most things fail, whether they be organisms or human institutions. Already there is a movement of power away from the nation state: upwards to global institutions and corporations to deal with global issues; downwards to communities of human dimension; and sideways by electronic means between citizens everywhere. There is a wide range of possibilities including forms of dictatorship and disaggregation of society.
The problems of politics will be as difficult as they are today: how to ensure greater citizen participation without creating chaos; how to establish forms of accountability to ensure that governance is by broad consent; and how to establish checks and balances to protect the public interest, and ensure enforcement without abuse. Current rhetoric about democracy well illustrates some of the dangers. Populism can too easily corrode values, and democracy can produce abusive results.
Let us hope without total confidence that by 2200 humans will have worked out, and will practice an ethical system in which the natural world has value not only for human welfare but also for and in itself. They may also be involved in spreading life beyond the Earth and colonizing Mars or other planets. The opportunities for our species seem as boundless as the hazards.
Working together, we may merit our survival. But our long-term prospects cannot be assured. Our present civilization may turn out to be a failure, an experiment which did not work, or which sank like a ship under the weight of the cargo of its own excesses. There is a touching Chinese poem from the time of the Tang dynasty with a message of hope:
"Thousands of boats pass by the side of the sunken ship. Ten thousand saplings shoot up beyond the withered tree."
But supposing the boats do not pass and the saplings do not shoot up. How long would it take for the Earth to recover from the human impact? How soon would our cities fall apart, soils regenerate, the animals and plants we have favoured find a more normal place in the natural environment, the waters and seas become clearer, the chemistry of the air return to what it was before we polluted it? Life itself, from the bottom of the seas, to the top of the atmosphere, is so robust that the human experience could become no more than a short and somewhat messy episode in the history of the Earth.
Above all let us remember how small and vulnerable we are as creatures of a particular environment at a particular moment in time. We are like microbes on the surface of an apple, on an insignificant tree, in an insignificant orchard, among billions of other insignificant orchards stretching over horizons beyond our sight or even our imagining.