Risking human extinction

Abstract

Of all humans so far, roughly ten per cent are alive with you and me. If human extinction occurred soon, our position in population history would have been fairly ordinary. But if, in contrast, humankind survived for many more centuries, perhaps colonizing the galaxy, then we could easily be among the earliest 0.001 per cent of all humans who will ever have lived. This could seem a very surprising position to be in — a point which is crucial to a “doomsday argument” originated by the cosmologist Brandon Carter. People who accept the argument, even in a weakened form which takes account of the fact that the world is probably indeterministic, will re-estimate the size of the threats to humankind, showing increased reluctance to believe that humans will survive for very long. Possible threats include nuclear and biological warfare; ozone layer destruction; greenhouse warming of a runaway kind; an environmental crisis caused by overpopulation; new diseases; disasters from genetic engineering or from nanotechnology; computers replacing humans entirely, as some people think would be desirable; the upsetting of a space-filling scalar field through an experiment at very high energies, as discussed in a recent book by England’s Astronomer Royal; and even the arguments of the many philosophers who see no duty to keep the human race in existence. But despite all such dangers and despite Carter’s disturbing argument, humans may well have a good chance of surviving the next five centuries.