Thursday, February 23, 2006

The Big Retirement Plan

Twenty-something years ago when the Lotus 1-2-3 integrated spreadsheet and graphic program knocked the socks off the business world, I used to teach people how to use it and even wrote a book on the subject. One exercise I had involved global population growth and how many of us the planet could tolerate before the ecosystem collapsed. The magic number in this case was 7 billion and the estimate to achieving it was around 2012

The planet's population is projected to reach 6.5 billion at 7:16 p.m. EST this Saturday, according to the U.S. Census Bureau and its World Population Clock.

Thomas Malthus, the 18th-century thinker who famously predicted the human population would outrun its food supply, would be astounded.

In 1798, when Malthus wrote his classic An Essay on the Principle of Population, barely a billion humans lived. Today, Earth's population teeters on the brink of a new milestone with 6.5 billion of us.

The clock, which operates continuously, estimates that each second 4.1 people are born and 1.8 people die. The clock figures are estimates, subject to error, given the difficulties of maintaining an accurate global population count.

However, the key concept -- that population levels are growing, but at a slower rate than in the past few decades -- reflects the consensus view of demographers. The current growth of world population, estimated at 1.1 percent a year, has slowed significantly from its peak of 2.1 percent annual growth between 1965 and 1970.

Today, a large portion of the world's population lives in nations that are at sub-replacement fertility, meaning the average woman has fewer than two children in her lifetime. Countries in this camp include former members of the Soviet Union, Japan and most of Europe.

The highest population growth rates emanate disproportionately from the poorest regions of Africa, the Middle East and the Indian subcontinent.

In 1950, less than 30 percent of people lived in areas defined as urban. Next year, the United Nations projects that more than half the world's population will be urban. Read more in Wired Magazine

This question of population leads us on to something called the 'Carter Catastrophe'. From what I can read and understand in an essay on the subject I read by Jim Holt, we shouldn't be worrying to much about those mounting credit card debts.

The end of the human race appears to be on the cards, statistically speaking at least and there's some rather compelling mathematics which suggests that the end is not too far away.

Do you ever lie awake at night wondering why you happen to be alive just now? Why it should be that your own particular bit of self-consciousness popped into e existence in the twentieth century and not, say, during the time of Cleopatra or 10 million years hence? If you do, and your musings take a sufficiently rigorous form, you might arrive at the conclusion that the human race is doomed to die out - and quickly.

A handful of cosmologists and philosophers have reached the same conclusion. Their reasoning is known as the Doomsday Argument. It goes like this:

Suppose humanity were to have a happier future, surviving thousands or millions of years into the future. And why not? The sun still has half its 10-billion-year life span to go. The earth's population might stabilise at 15 billion or so, and our successors could even colonise other parts of the galaxy, allowing a far greater increase in their numbers. But think what that means: Nearly every human who will ever exist will live in the distant future. This would make us unusual in the extreme.

Assume, quite conservatively, that a billion new people will be born every decade until the sun burns out. That makes a total of 500 quadrillion people. At most, 40 billion people have either lived in the past or are living now. Thus we would be among the first 0.00001 percent of all members of the human species to exist. Are we really so special?

But suppose, contrariwise, that humanity will be wiped out imminently, that some sort of apocalypse is around the corner. Then it is quite reasonable, statistically speaking, that our moment is the present. After all, more than 6 billion of the 40 billion humans who have ever lived are alive today, and with no future epochs to live in, this is far and away the most likely time to exist. Conclusion: Doom soon.

Even as transcendental 'a priori' arguments go, this one is pretty breathtaking. For economy of premise and extravagance of conclusion, it rivals Saint Anselm's derivation of God's existence from the idea of perfection and Donald Davidson's proof that most of what we believe must be true or else our words would not refer to the right things.

As far as anyone knows, the Doomsday Argument was first publicly broached in 1983 at a meeting of the Royal Society in London. Its apparent author was Brandon Carter, a British astrophysicist (now living in France) famous for his work on black holes. A decade earlier, Carter had baptized the much-debated anthropic principle, which purports to explain why the laws of physics look the way they do: If they were any different, life could not have emerged, and, hence, we would not be here to observe them.

Perhaps you are skeptical about the Doomsday Argument. It looks like a logical trick. How could an abstract argument have such an experientially rich upshot? Yet it is difficult to find anything amiss in its logic. The sole assumption it requires - an eminently plausible one - is that if humanity endures, our cumulative numbers will increase. And the inference it makes is justified by the principle of probability known as Bayes' theorem, which dictates how a piece of evidence (we are living now) should affect the likelihoods we assign to competing hypotheses (doom sooner versus doom later).

Furthermore, the Doomsday Argument may not seem so unlikely once you consider all the forms doom could actually take. Don't think H5N1 greenhouse gases, weapons of mass destruction - just look up. An asteroid might bump into our planet (one wonders whether the Doomsday Argument occurred to the dinosaurs 65 million years ago). The Swift-Tuttle comet - dubbed the "Doomsday Rock" by the media - will be swinging awfully close on or about 14 August 2126.


Anonymous said...

Just time for a nice cup of tea then.

Anonymous said...

One problem with the ever increasing population argument is how would these extra billions of people be fed?
Ever see the film Soylent Green?

Anonymous said...

Dr Moores, as evidence on this site shows you are often ahead of the game on news items, I am relying on you to warn me when it is time to bend-down and kiss my a*** goodbye!