WHAT'S GOING TO GET YOU FIRST?

Nuclear war, climate change, mutant disease, pollution, meteorites... the number of possible ways in which the world as we know it might come to an untimely end has rarely seemed so high. This directory assesses the probability (including the latest betting) of some of the most widely- feared doom scenarios; and, on page 8, a guide to cults that claim to know the details

Doom is not what it used to be. In the Book of Revelation, shortly before the sun turns black and the moon becomes as blood, the four outriders of the apocalypse appear - seated on steeds representing conquest, war, famine and pestilence. As the new millennium approaches, our ideas about how life might end have both undergone a remarkable transformation - and remained remarkably unchanged.

Doom has become a largely secular phenomenon. The Lamb, the Beast and the Four Horsemen have been replaced by global warming or gender-bending chemicals. And, whereas our forebears probably only thought about doom on a Sunday, after a particularly fiery sermon, we read about it every day in the newspapers. Yet war, famine and pestilence are still among the most likely doomsday scenarios - as the directory below suggests, .

Indeed, war is favourite, at 500:1, in the end-of-the-world stakes that William Hill have compiled to accompany this article. As a rule, they don't take bets on this eventuality, for the obvious reason that there would be no one to collect the winnings, or pay them. The odds offered here allow for the possibility of up to 1,000 survivors (worldwide) of the "End"; and the bookies - if they survived - would pay out to any of those survivors who could prove they had placed a winning bet.

ANARCHY

Anarchy is a much abused word. As used by thinkers such as Proudhon or Kropotkin, it meant decentralised living in village communities - the "small is beautiful" ideal of EF Schumacher. But in colloquial, late-20th century parlance it means a gradual descent into crime, violence and lawlessness, as the authority of the state collapses. Over the past 30 years this vision of urban, sometimes post-nuclear, apocalypse has become a cinematic cliche, figuring in a string of films: Mad Max, Blade Runner, Escape from New York. Could fiction prefigure reality?

Three years ago the US writer Robert Kaplan wrote an influential essay in the journal Atlantic Monthly describing the collapse of state power in many African countries - subsequently expanded in his book The Ends of the Earth: a Journey at the Dawn of the 21st Century. Kaplan argues that the world is becoming an infinitely more dangerous place as distinctions weaken "between states and armies, armies and civilians, and armies and criminal gangs"; he also believes that this diagnosis applies outside Africa - notably in Asia and in urban North America, where economic growth has created riches for a few but deprivation, leading to desperation, for a new international underclass. This is a future where the privileged lock themselves away in high-walled estates with private security patrols while, outside, basic services - such as health care, law and order - and an underclass struggle to survive.

The key factor is social cohesion - or the lack of it. Globally, and within nations, the "haves" and the "have nots" are growing further apart: the total wealth of the world's 358 billionaires now equals the combined incomes of the poorest 2.3 billion people. There is growing evidence to link social inequity with social instability and rising levels of crime, particularly crimes of violence. Serial killing is on the increase and so is gang warfare - bikers wars in Scandinavia, riots in the immigrant suburbs of Paris, drug murders in cities everywhere. And in the US, where recent bombings in Oklahoma and Atlanta have revealed the existence of a network of 400 right-wing gun-carrying militias, disenchantment with government has coincided with an upsurge in "amateur" terrorism. The leading security consultancy Control Risk recently warned that the threat posed by extremist doomsday cults, single-issue groups and militias was global and likely to intensify up to the turn of the century.

HOW LIKELY? One of the stronger possibilities: social breakdown is already starting to happen in some parts of the world. But it might not actually wipe out the entire human race.

WILLIAM HILL'S ODDS (against life as we know it being destroyed by anarchy before 2097): 50,000:1.

CLIMATIC EVENTS

Once known as Acts of God, though perhaps more accurately described as Acts of Man, these include freak weather and unpredictable shifts in the climate. Such changes are already upon us and their cause is well-known - global warming, the heating of the atmosphere caused by the burning of fossil fuels.

Scientists can still be found who reject the idea that global warming exists but the international scientific consensus, as expressed by the UN's Intergovernmental Panel on Climate Change, is that there is already a "discernible human influence" on the planet's climate. Certainly the signs are there. First, it has been abnormally hot of late. The growing season is longer, by about a week, and the outriders of apocalypse have been gathering - the pests, like aphids, that are predicted to flourish in the UK as the climate warms. And, while there have been no signs of the sun turning black or the moon to blood, there have been storms.

Insurance claims for weather-related disasters have risen spectacularly, from $16bn for the whole of the 1980s to $48bn for the first half of the 1990s alone. In 1991 winds of 170 mph - more than double hurricane force - hit Bangla-desh, killing 139,000 people. In Europe, big winter storms are becoming more common and in the UK are predicted to be 30 per cent more frequent by the middle of the next century.

If emissions from cars and factories continue at current levels, global temperature may rise by 2.5C in the next century. Expansion of the oceans could raise sea-levels by 1.2 metres, flooding large areas of southern China, Bangladesh, Egypt, the Netherlands and Florida, drowning many Pacific islands and radically altering the shape of eastern England's coastline. This, combined with the possible speed and scale of disruption to agriculture, and consequently to economies, could spell the end to life as we know it. (See also Disease, Drought and Famine.)

HOW LIKELY? More likely to make life very uncomfortable than to wipe us out altogether.

WILLIAM HILL'S ODDS (against life as we know it being destroyed by climate change before 2097): 250,000:1.

DISEASE

A raft of "new" diseases now threatens the human species. Some are the result of our exploitation of the rainforests where viruses that have lain dormant for millennia have been disturbed. Others are due to genetic adaptations bacteria and viruses have made to counter our attempts to destroy them. And we are then providing ideal conditions in which these infections can flourish; a new era of sexual freedom; a boom in foreign travel, with tourists transporting germs between continents; and the unprecedented growth of slums and shanties in the Third World.

Ebola virus, which has a near 100 per cent fatality rate and for which there is as yet no medical cure, is typical of the diseases that have been "released" from the wild. Aids may have a similar origin. Between 60 and 70 million people, about one per cent of the world's population, may have contracted the HIV virus by the end of the decade. In the Middle Ages, the Black Death killed about 25 million people, a third of Europe's population. Aids has already killed about 10 million and has strained parts of Africa and south-east Asia to breaking point.

Climate change will bring "widespread risks" to human health, according to the World Health Organisation, with big rises in malaria, heat stroke, asthma, parasitic, food and water-related infections, heart and lung disorders, skin cancer and eye disease. Many other "new" diseases appear to be man- made, notably the "diseases of affluence" such as obesity, cancers and heart disease, and the various scares around intensive food production. Food poisoning, for example, has risen threefold in the UK in the last decade.

Some of the old diseases we thought we had conquered, like TB, malaria, diphtheria and cholera, are staging a comeback. The reasons include poverty and the overuse of antibiotics, which has bred drug-resistant bacteria. The number of strains of pneumonia bacteria resistant to penicillin grew from six to 44 per cent in the 1980s, for example. More alarmingly, doctors have recently discovered a stomach bacterium that thrives on antibiotics.

HOW LIKELY? Near the top of the list. A major own goal by humanity.

WILLIAM HILL'S ODDS (against the human race being wiped out by disease before 2097): 5,000:1.

DROUGHT

Globally, water use has tripled since the 1950s. Human beings already use half the world's freshwater run-off. According to the ecologist Dr Norman Myers, population growth alone - without allowing for increases in consumption, which look inevitable - will take this to three-quarters by the year 2025. The consequences are visible throughout the world's landscapes, as soil erodes, deserts expand, wetlands vanish and lakes, seas and rivers shrink. Perhaps the most poignant example is the Aral Sea in central Asia, which has lost three-quarters of its water because of river diversions. In Britain water demand during hot weather is forecast to grow by 35 per cent over the next 25 years - and hot weather will become much more frequent. By 2050 hot dry summers, such as 1995's, which in the past have happened only once in 90 years, will be occurring one year out of every three.

The implications for peace, health, food production and the survival of wild plants and animals are enormous. Chronic water shortages already affect 40 per cent of the world's population. So-called "water wars" between states over shared lakes and rivers could break out - the Middle East and north-east Africa are likely flashpoints. According to Washington's World-watch Institute, conflict between Israeli settlers and Arabs over water rights probably contributed to the Palestinian intifada. Rationing and metering may increase the spread of diseases such as dysentery and the "mining" of underground aquifers for fresh water is already causing widespread subsidence in cities. Mexico City, for example, is sinking by up to 8in a year.

HOW LIKELY? Less likely, and more manageable, than most.

WILLIAM HILL'S ODDS (against the human race being wiped out by drought before 2097): 100,000:1.

FAMINE

To say that the world faces a hungry future risks ignoring the fact that nearly a seventh of its population - that's 800 million people - are already chronically undernourished. But many experts, including those at the World Bank, which recently predicted an "unthinkable nightmare" of world hunger unless urgent action was taken, believe things could get much worse.

In 1995, for the third year running, the world produced less food than it ate, and its "carry-over" stocks of emergency grain supplies sank to a record low, enough to cover only 48 days of consumption. Good harvests this year may have redeemed the situation a little but the key indicator of grain production per person has been on a downward trend since the mid-1980s.

Vegetarianism is one strategy for survival, providing roughly five times more protein per acre than a meat-based diet, but many fast-developing Third World countries see meat as a form of dietary "improvement" - China now consumes twice as much red meat as the United States. Many other solutions bring their own problems, too. Genetic engineering could produce vast monocultures vulnerable to a single pest. And any food expansion strategy has to take account of water shortages, declining soil fertility and the disruptions caused by climate change - hence the conclusion of experts like Lester Brown, president of the Worldwatch Institute, that we may be witnessing a shift in the world's food economy "from a long-accustomed period of overall abundance to one of scarcity". And although the West may be able to buy itself out of the hunger, it may find the conflict generated by hunger more difficult to avoid (see War).

HOW LIKELY? A real threat, although perhaps more as an indirect cause than as a direct one.

WILLIAM HILL'S ODDS (against the human race being wiped out by famine before 2097): 75,000:1.

NATURAL CAUSES

Most things that have a beginning also have an end, and since the Big Bang theory about the origins of the universe (which argues that it began in an unimaginably explosive "singularity" between 9-14 million years ago) has now eclipsed steady-state theories (which contend that matter is continually being created), a Big Crunch is ultimately, in theory, unavoidable.

Before that happens, however, several intermediate endings have to be negotiated. It used to be thought, for example, that industrial man was the fortunate resident of the latest "inter-glacial" - the warm periods during Ice Ages in which life has briefly rioted before the glaciers returned. Glaciations are triggered by changes in the Earth's orbit around the Sun, but since the ice sheets withdrew from Britain around 10-15,000 years ago, and interglacials last as little as 20,000 years, the glaciers seemed due to return in another 5,000 years or so.

Global warming may have led to the cancellation of the next glaciation, although some predict it will produce sudden and unexpected shifts in climate and therefore accelerate it. It is certainly not unreasonable to expect one sooner or later. Other, more awe-inspiring possibilities include being sucked into a drifting Black Hole or incinerated when the Sun nears the end of its stellar life-cycle and turns into a giant star, a Supernova or a White Dwarf.

As yet, we do not know for sure whether the universe is still expanding under the influence of the Big Bang. But if the Big Crunch does come, all is not lost. According to the Oscillating Universe theory, the Big Crunch may only be a prelude to another Big Bang, a fresh Universe, new life on Earth (or something like it) and a lot more worries about the future.

HOW LIKELY? Ultimately, a certainty; but life will probably be extinguished by something else first.

WILLIAM HILL'S ODDS (against the world ending in the course of the natural development of the Universe before 2097): 50 million: 1.

OVER-POPULATION

Ever since Malthus, who argued 200 years ago that population growth would inevitably outstrip world food resources and advocated "moral restraint" as the solution, the rise in human numbers has been a leading component in global doomsday scenarios. There are roughly 90 million additional people on the planet each year (nearly three people a second).

The UN regularly reassesses its estimates about the future size of the world's population, as fertility rates fluctuate. The latest figure is 9.4 billion by the year 2050, compared with 5.8 billion today, but estimates for a century later (2150) have ranged from 28 billion (and rising) to 3 billion (and falling). If current growth rates continued, for example, there would be over 600 billion of us living in 150 years' time.

How many people can the Earth support? According to the American academic Joel Cohen, who wrote a book with this title, answers have ranged between 1 billion and 1,000 billion. But already we are pre-empting a huge share of the planet's sunshine, energy, rainfall and land, pushing other species into isolation and extinction. And calculations of living-space or standing- room - it used to be said you could get the entire population of the UK on the Isle of Wight and still have room to spare - fail to take into account a range of biological, social and psychological factors. A world in which the total number of species was measured in hundreds, instead of millions, would probably be biologically unstable, for example. And if recent outbreaks of "rage" - road rage, noise rage - are a measure of high-density living, and thus, indirectly, of growing human numbers, what further conflicts might erupt if the crowds were inescapable?

HOW LIKELY? A long shot. We might just adapt.

WILLIAM HILL'S ODDS (against the human race being wiped out as a direct result of over-population before 2097): 25 million: 1.

SPACE INVADERS

If you believe that aliens have already visited the earth - and 47 per cent of Americans do, according to a recent Gallup poll - then the scenario of the film Independence Day, in which the Earth is invaded by extra-terrestrials, may well rank high on your worry list. As John Leslie points out in his book The End of the World: The Science and Ethics of Human Extinction, there are several good reasons why the failure - so far - of our search for extra-terrestrial life does not mean the threat can be discounted. First, our searches have been relatively primitive; second, there may be lots of advanced civilisations in the universe, but they may be listening rather than broadcasting, to avoid attracting attention.

A more plausible threat, however, comes from the impact of meteorites, asteroids or comets. Astronomers say that the chances of being hit by a big asteroid are fairly remote - about one in 2 million years. For a small asteroid, the odds come down to one in 2,000 years. But even an asteroid only 50m across would be enough to devastate a country the size of England. Earth has been peppered by asteroids throughout its history and at least one of them, which hit the planet about 65 million years ago, is associated with the extinction of the dinosaurs. In that instance a trillion tons of rock up to 20km across and moving at about 20km a second exploded in what is now Mexico with an energy of 100 million megatons - more than 10,000 times the energy locked up in the world's nuclear arsenals at their peak. The result was huge tidal waves and forest fires, darkness lasting several months, caused by clouds of dust, and hurricanes moving at nearly the speed of sound.

There are about 100 million asteroids in space, an estimated 100,000 of them in an orbit which takes them near to the Earth. Some scientists believe nuclear weapons could be used to blow them off course. Over the last two decades bits of comets have hit both Jupiter and the Sun. Earth's next (known) date with inter-stellar destiny will be in 2126 when the comet Swift-Tuttle will come within two weeks of hitting it.

HOW LIKELY? A dark horse.

WILLIAM HILL'S ODDS against the world being conquered by aliens before 2097: 500,000:1; against life on Earth being wiped out by a cosmic collision before 2097: 10,000:1.

POLLUTION

If extra-terrestrials existed, they might well decide to leave the Earth uninvaded on the grounds that for the last couple of centuries the human race has been conducting a large-scale experiment in chemical toxicity. An estimated 100,000 man-made chemicals have been released into the biosphere, only a small minority of which have tested for potential hazards. A recent study of the 50,000 industrial chemicals in use - excluding pesticides, food additives, cosmetics and drugs - found there was no information on 80 per cent and big gaps on the rest. Two thirds of pesticides do not even have "minimal toxicity information".

Toxins produced by man are ubiquitous in the modern world, from DDT in human breast milk to PCBs in polar bears and radiation from Chernobyl falling as rain on Snowdonia. They puff out from car exhausts, cling as residues to food, contaminate soils and waters. Sometimes the amounts are microscopic - we are aware of them only because of increasingly sophisticated measuring devices. But that does not necessarily mean they are innocuous.

Pollution can kill but more often it damages or debilitates, and although cause and effect are hard to establish, warning signs have been accumulating. There is direct evidence of deteriorating health, ranging from deformities and die-offs among animals such as frogs - one of the main "sentinel" species - to rising rates of cancer and declining fertility in humans. In Our Stolen Future, Theo Colborn pointed the finger at a range of hormone- disrupting chemicals, like PCBs, that are now part of the fabric of industrial society. Their presence, she argued, has already lowered sperm counts, harmed babies' brains in the womb, impaired intelligence and altered behaviour. Unless such chemicals are banned, she says, men could become infertile by the middle of the next century.

HOW LIKELY? More likely to cause extreme discomfort than extinction; but there are some nasty shocks in store.

WILLIAM HILL'S ODDS (against the human race being wiped out by pollution before 2097): 1 million: 1.

WAR

The atomic bomb that destroyed Hiroshima in 1945, killing or wounding 150,000 and destroying three-quarters of the city, had a destructive energy measured at 10 kilotons - equivalent to 10,000 tons of the explosive TNT. Today, despite the ending of the Cold War and the evidence of substantial progress towards disarmament, the world still houses enough nuclear weaponry to detonate the equivalent of 600,000 Hiroshima bombs.

In the early 1980s, when nuclear war still seemed possible, and the Government was issuing copies of Protect and Survive, telling us how to rig up home- made bunkers, the World Health Organisation estimated that such a war would kill off half the world's population more or less immediately. Yet, although the mushroom cloud that was so evocative an image of Armageddon looks a little dated now, the horizon is far from clear.

First, the New World Order supposed to follow the collapse of Communism has itself undergone fission, into a patchwork of regional conflicts, not merely in conventionally strife-ridden regions such as the Middle East, but in Yugoslavia and the former Soviet Union. These conflicts mix nationalism, tribalism and religious fundamentalism and have generated terrorist activity worldwide. But there will almost certainly be new sources of conflict in the next century, sparked off by climate change, centring on issues such as land, water and food and generating millions of "environmental" refugees. Suppose the participants in such conflicts got their hands on bits of the remaining nuclear stockpile or on the large stockpiles of biological weapons that are even less regulated ...

The evidence suggests that such dangers must be taken seriously. Saddam Hussein threatened chemical warfare in the Gulf in 1991. Last year, the extremist Japanese sect Aum Shinrikyo attacked commuters with the nerve gas sarin. And as Russia has dissolved into something approaching internal chaos, worries have grown about nuclear accidents and weapons being sold on to the black market. These scenarios are close to death by anarchy.

An international coalition of over 60 leading generals and admirals recently warned of the dangers of terrorism, proliferation and a new nuclear arms race. Anti-nuclear bunkers might still come in handy.

HOW LIKELY? Probably still the biggest risk.

WILLIAM HILL'S ODDS (against the human race being wiped out by war before 2097): 500:1.

Doomsday Stakes (clockwise from top left): William Hill offers 500:1 against life being wiped out by war; by climate change, 250,000:1; by anarchy, 50,000:1; by space invaders, 500,000:1; by pollution, 1 million:1; by drought, 100,000:1

The chances of all human life being wiped out by famine (above) are slight; but widespread famine could easily provoke other doomsday scenarios, such as anarchy and war (below)