Humans: a reflection
Where are we coming from? Where are we now? Where are we going? There are no easy answers. For all of us the past as well as the future is an almost unknown country; and the present is a doubtful place with signs pointing in different directions.
First we need to establish the perspective. Humans are an infinitesimal part of the living world (0.00007 percent of estimated living species). Each of us has ten times more bacterial than body cells. Our species is relatively new. No one was around to record the evolution of the first human-like creatures from our ancestral apes in Africa some 4 million years ago. They left the trees for the savannah, became relatively hairless, and learnt 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: among them were the Neanderthals and (as discovered in the last few months) the Denisovans. Another offshoot may still have been living on the Indonesian island of Flores as recently as 16,000 years ago - a mere blink in geological time.
So far through analysis of fossils and work on current humans, we have been able to trace our own genealogy back some 150,000 years. All other branches of humans are now extinct, but many of us share at least a small proportion of their genes.
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 last spasm of the Pleistocene ice ages.
There could have been another reduction of human numbers during the so-called Younger Dryas event some 12,000 years ago, when the Gulf Stream probably changed direction. We know from recent history what big effects volcanic eruptions can have: Mount Laki in Iceland in 1783, Tambora in 1815, Krakatoa in 1883 and Iceland again last year.
Then there were other disasters: for example major epidemics, like the Plague of Justinian in 540, or the Black Death which devastated populations world wide in the 14th century; or even a hit from space (if the object which devastated part of Siberia just over a hundred years ago had hit London, there would have been nothing left within the M25 ring road).
Whatever these recent crises affecting human numbers, all modern humans are fairly close cousins. There are more genetic differences between Africans than there are between African 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: use of fire, language, music, symbolic thought, art in its many forms, 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? Whenever the change took place, the extraordinary development of human brain power, which has produced ourselves, occupies less than one 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 the 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. With a vast increase in human population came towns and eventually cities. Tribal communities evolved into complex hierarchical societies. For a rich variety of reasons such societies rose and fell, and usually, but not always, recovered. The pulse of civilization has always been irregular.
Before the industrial revolution some 250 years ago, the effects of human activity were local, or at most regional, rather than global. Now the impact is indeed global, indeed many geologists would like to establish a new geological epoch - the Anthropocene - to mark the extraordinary effect that human activity has had on the surface of the Earth.
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 my view there are six main factors which have driven this transformation. Of these population issues are often ignored as somehow embarrassing or mixed up in religion and development economics; most people are broadly aware of land resource and waste problems, although far from accepting the necessary remedies; water issues, both fresh and salt, have had a lot of publicity, and already affect most people on Earth; climate change with all its implications for atmospheric chemistry is also broadly understood, apart from 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 until recently escaped the attention it should have received.
Here we remain ignorant of our own ignorance. Yet in this area 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. It arises from the introduction of new technologies. In a recent book Martin Rees, former President of the Royal Society, explored the dangers arising from human inventiveness, folly, wickedness and sheer inadvertence. The ramifications of information technology, nano-technology, 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.
In broad terms we suffer from creeping impoverishment of the biosphere. As E. O. Wilson said in his book The Creation:
"We have, all by our bipedal, wobbly-headed selves, altered Earth's atmosphere and climate away from the norm. We have spread thousands of toxic chemicals world wide, appropriated 40 percent of the solar energy available for photosynthesis, converted almost all of the most easily arable land, dammed most of the rivers, raised the planet sea level, and now, in a manner likely to get everyone's attention like nothing else before it, we are close to running out of fresh water."
What then are we to expect? How are we to recognize that the last 250 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. Are we near to those stops?
In September 2009 the magazine Nature published an article by Johan Rockstrom and others identifying nine scientific stops or boundaries which humans would cross at their peril. Three, they said, had already been crossed: climate change; loss of biodiversity; and interference with the nitrogen and phosphorus levels. The other six were stratospheric ozone depletion; ocean acidification; use of fresh water; changes in land use; chemical pollution; and atmospheric aerosol loading.
We can all have our own lists and calculations of the dangers. I have already suggested some of mine. Going back to them, I have no doubt that we have to rethink how we run our society. That means confronting the major issue of our own multiplication in all its aspects; looking again at a lot of economics; giving high priority to conservation of the natural world; working out new ways of generating energy; dispersing and to some extent localizing the ways by which we feed ourselves; managing and adapting to climate change, or as I prefer to call it climate destabilization; and creating the necessary institutional means of coping with global problems. In the future global village we cannot afford to have many village idiots.
We all suffer from a disease of what has been called conceptual sclerosis. Little is more difficult than learning to think differently, above all when problems go to the roots of the conventional wisdom. Nurture is often at war with nature. Old ideas haunt us like ghosts.
It is time now to turn to the future of our species in a world which is changing under human pressure before our eyes. Bear in mind that nearly all forecasting turns out to the wrong. We do well to expect the unexpected.
There are the obvious challenges. Some relate to the Earth as a whole: for example the natural disruptions known throughout history, volcanic explosions, earthquakes, impacts of extraterrestrial objects, and variations in ecosystems, including patterns of disease. Climate change may well have redistributed human as well as other organisms. Then there are the specific problems of humanity, including the widening divisions between rich and poor within and between countries, the high vulnerability of cities, the growth of terrorism, the risks of war with unimaginably horrible weapons, and the exhaustion of often irreplaceable resources.
But this is not the whole story. Nor does it cover changes in the balance of power between East and West, and North and South. That is a huge subject in itself: political, social, economic and technological. Indeed such changes may come to represent the most important for thousands of years, and they seem to be accelerating.
It would be rash to attempt to forecast how the world will look even a hundred years from now. But humans will be much the same wherever they are, and it may be useful to jump that hundred years, and from this vantage look backwards. In doing so, I shall assume, I hope correctly, that humans will have faced up to and coped with at least some of the problems I have discussed. People are not stupid. So what will the world look like?
First humans are likely to be living in a more globalized world of rapid communication. Ideas and units of information - or memes - will pass almost instantaneously between countries, communities and individuals. The wiring of the planet with fibre optics, cellular wireless, satellites and digital television is already transforming human relationships. More than ever in the past there will be something like a single human civilization. Humans can be regarded like certain species of ants as a superorganism.
Human numbers in cities and elsewhere will almost certainly be reduced, but some people will live much longer, bringing its own train of problems. Their distribution will be different. Women will have a more important role. 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 - almost 7 billion or even 9 billion by mid-century.
Communities are likely to be more dispersed without the daily tides of people flowing in and out of cities for work. Current obsessions with ever-increasing consumption will be replaced by the need to make better use of resources. Agriculture will be more local and specialized with greater reliance on hydroponics. Energy and transport systems will be decentralized. Archaeologists of the future may even wonder what all those roads were for.
Then there are developments in information technology. They raise the question of evolution itself. At present we can alter isolated genes while disregarding the complexity - and totality - of what genes can do. Here the law of unintended consequences is important. Already chips have been inserted into humans for a variety of purposes. We can even insert extra chromosomes in the knowledge that they will not be heritable.
On the one hand humans may thereby be liberated from many current drudgeries. Houses may be able to clean themselves, robots may produce meals on demand, cars may drive under remote instruction, and evolution of desirable characteristics could even be automated. All this seems hardly imaginable 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 transfer information, are having alarming effects. Even the functioning of the human brain may already be changing.
The implications for governance reach equally wide. In some areas good regulation will be more important than ever. In the words of the title 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 more human dimension; and sideways by electronic means between citizens everywhere.
Let us hope without total confidence that by 2100 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. The human superorganism must take its place alongside other super-organisms.
For the long term I hesitate to speculate. Tectonic plate movement will shift the relationship between land and sea. Changes in oxygen levels in the atmosphere may affect the viability of life itself. The human species may even change its shape, assuming some are still alive to tell the tale. For example given the evolutionary significance of our brains and the current hazards of childbirth, we might imagine a sort of human marsupial in which women gave birth earlier in the reproductive process, and developed a kind of pouch.
I sometimes wonder how long it would take for the Earth to recover from the human impact. Future visitors from outer space might well be puzzled by the fossil remains of ourselves and the agglomerations we call cities. They might also wonder at the fossils of the other animals and plants we have so abruptly adapted for our own purposes. In the future rats could be as big as dogs, water hyacinths could block lakes, and micro-organisms could go macro. But they should know, as should we, that life itself, from the bottom of the seas to the top of the atmosphere, is so robust that the dominance of any one species could be no more than a relatively short episode in the history of life on Earth.
Above all we must recognize how small and vulnerable we are as creatures of a particular environment at a particular moment in time. Let us enjoy it while we can.