James Lovelock has written:
Humans on the Earth behave in some ways like a pathogenic organism, or like the cells of a tumour or neoplasm. We have grown in numbers and disturbance to Gaia, to the point where our presence is perceptibly disturbing … the human species is now so numerous as to constitute a serious planetary malady. Gaia is suffering from Disseminated Primatemaia, a plague of people.
Around 65 million years ago the dinosaurs and three quarters of all other species suddenly perished. The cause is disputed, but many scientists believe the mass extinction was the result of a meteorite colliding with the Earth. Today species are disappearing at a rate that is set to surpass that last great extinction. The cause is not any cosmic catastrophe. As Lovelock says, it is a plague of people.
‘Darwin’s dice have rolled badly for Earth,’ Wilson points out. The lucky throw that brought the human species to its present power has meant ruin for countless other life forms. When humans arrived in the New World around twelve thousand years ago, the continent abounded in mammoths, mastodons, camels, giant ground sloths and dozens of similar species. Most of these indigenous species were hunted to extinction. North America lost over 70 per cent and South America 80 per cent of its large mammals, according to Diamond.
The destruction of the natural world is not the result of global capitalism, industrialisation, ‘Western civilisation’ or any flaw in human institutions. It is a consequence of the evolutionary success of an exceptionally rapacious primate. Throughout all of history and prehistory, human advance has coincided with ecological devastation.
It is true that a few traditional peoples lived in balance with the Earth for long periods. The Inuit and the Bushmen stumbled into ways of life in which their footprint was slight. We cannot tread the Earth so lightly. Homo rapiens has become too numerous.
The study of population is not a very exact science. No one forecast the population collapse that is occurring in post-communist European Russia, or the scale of the fall in fertility that is under way in much of the world. The margin of error in calculations of fertility and life expectancy is large. Even so, a further large increase is inevitable. As Morrison observes, ‘Even if we assume a declining birth rate due to social factors and a rising death rate due to starvation, disease and genocide, the present global population of over 6 billion will grow by at least 1.2 billion by the year 2050.’
A human population of approaching 8 billion can be maintained only by desolating the Earth. If wild habitat is given over to human cultivation and habitation, if rainforests can be turned into green deserts, if genetic engineering enables ever-higher yields to be extorted from the thinning soils – then humans will have created for themselves a new geological era, the Eremozoic, the Era of Solitude, in which little remains on the Earth but themselves and the prosthetic environment that keeps them alive.
It is a hideous vision, but it is only a nightmare. Either the Earth’s self-regulating mechanisms will make the planet less habitable for humans or the side effects of their own activities will cut short the current growth in their numbers.
Lovelock suggests four possible outcomes of disseminated primatemaia: ‘destruction of the invading disease organisms; chronic infection; destruction of the host; or symbiosis – a lasting relationship of mutual benefit to the host and invader’.
Of the four outcomes, the last is the least likely. Humanity will never initiate a symbiosis with the Earth. Even so, it will not destroy its planetary host, Lovelock’s third possible outcome. The biosphere is older and stronger than they will ever be. As Margulis writes, ‘No human culture, despite its inventiveness, can kill life on this planet, were it even to try.’
Nor can humans chronically infect their host. True, human activity is already altering the planetary balance. The production of greenhouse gases has changed global ecosystems irreversibly. With worldwide industrialisation, such changes can only accelerate. In a worst-case scenario that some scientists are taking seriously, climate change could wipe out populous coastal countries such as Bangladesh and trigger agricultural failure in other parts of the world, spelling disaster for billions of people, before the end of the present century.
The scale of the change afoot cannot be known with certainty. In a chaotic system even the near future cannot be predicted accurately. Yet it seems likely that the conditions of life are shifting for much of humankind, with large segments of it facing much less hospitable climates. As Lovelock has suggested, climate change may be a mechanism through which the planet eases its human burden.
As a side effect of climate change, new patterns of disease could trim the human population. Our bodies are bacterial communities, linked indissolubly with a largely bacterial biosphere. Epidemiology and microbiology are better guides to our future than any of our hopes or plans.
War could have a major impact. Writing at the turn of the nineteenth century, Thomas Malthus named war as being one of the ways – along with recurrent famines – in which population and resources were kept in balance. Malthus’s argument was satirised in the twentieth century by Leonard C. Lewin:
Man, like all other animals, is subject to the continuing process of adapting to the limitations of his environment. But the principal mechanism he has utilised for this purpose is unique among living creatures. To forestall the inevitable historical cycles of inadequate food supply, post-Neolithic man destroys surplus members of his own species by organised warfare.
The irony is misplaced. War has rarely resulted in any long-term reduction of human numbers. Yet today its impact could be considerable. It is not only that weapons of mass destruction – notably biological and (soon) genetic weapons – are more fearsome than before. More, their impact on the life-support systems of human society is likely to be greater. A globalised world is a delicate construction. A vastly greater population than hitherto is dependent on far-flung supply networks, and any war on the scale of the larger conflicts of the twentieth century could have the effect of culling the population in the way Malthus described.
In 1600 the human population was about half a billion. In the 1990s it increased by the same amount. People who are now over forty have lived through a doubling of the world’s human population. It is natural for them to think that these numbers will be maintained. Natural, but – unless humans really are different from all other animals – mistaken.
The human population growth that has taken place over the past few hundred years resembles nothing so much as the spikes that occur in the numbers of rabbits, house mice and plague rats. Like them, it can only be short-lived. Already fertility is falling throughout much of the world. As Morrison observes, humans are like other animals in responding to stress. They react to scarcity and overcrowding by tuning down the reproductive urge:
Many other animals seem to have a hormone-regulated response to environmental stress that switches their metabolism into a more economical mode whenever resources become scarce. Inevitably, the energy-hungry processes of reproduction are the first to be targeted.… The telltale hormonal signature of this process … has been identified in captive lowland gorillas, and in women.
In responding to environmental stress by ceasing to breed, humans are no different from other mammals.
The current spike in human numbers may come to an end for any number of reasons – climate change, new patterns of disease, the side effects of war, a downward spiral in the birth rate, or a mix of these and other, unknown factors. Whatever brings about its end, it is an aberration:
… if the human plague is really as normal as it looks, then the collapse curve should mirror the population growth curve. This means that the bulk of the collapse will not take much more than one hundred years, and by the year 2150 the biosphere should be safely back to its preplague population of Homo sapiens – somewhere between 0.5 and 1 billion.
Humans are like any other plague animal. They cannot destroy the Earth, but they can easily wreck the environment that sustains them. The most likely of Lovelock’s four outcomes is a version of the first, in which disseminated primatemaia is cured by a large-scale decline in human numbers.