As well as these various accepted and relatively widely-known risks to the continued survival of the human animal, there are plenty of more obscure dangers that may elevate as current technological levels continue to advance in sophistication.
It has previously been noted that the task of anticipating future technological development is a haphazard occupation at best, but the question of mankind’s survival cannot be properly addressed without at least some extrapolation based on technologies currently in use or high level development.
One such is nanotechnology, which in its optimal form will produce self-replicating artificial molecules that can ‘feed’ on any material in the surrounding environment.
The malicious use of these devices would of course lead to disastrous consequences, but equally notable is the possibility of accidental misuse, leading to the infamous ‘grey goo’ scenario (a term first used in Engines of Creation by nanotechnologist Eric Drexler) where all matter on planet Earth is converted into tiny nanomachines whose replication is uncontrollable.
Runaway Particle Physics
Particle physics experiments could in theory generate runaway reactions with results varying from the destruction of the laboratory, continent, planet or even the universe itself.
As early as the first atomic bomb test in 1945, Robert Oppenheimer instructed physicist Hans Bethe to perform calculations to ensure that the detonation would not spark a chain fusion reaction and ignite the Earth’s atmosphere.
Even now in particle physics laboratories such as CERN, similar risk calculations are undertaken before each experiment begins in order to ascertain exactly how remote the possibility is that particle accelerators may accidentally create a black hole or an unnatural atomic template which binds other matter, thus collapsing spacetime into a void.
Artificial Existence and Philosophy
Further from extrapolation into speculation of a more science-fiction or philosophically orientated nature, even more possibilities for human extinction exist.
If the human species only exists as part of an intricate computer simulation being run by some other power, external factors could cause this simulation to be shut down.
At some point in the future humanity could choose to create an artificial intelligence or superintelligence, and so the possibility exists that this device or creature would decided that it no longer required its creators, either through faulty programming or independent awareness, and exterminate them.
As an alternative to this particular case, humans could choose to upload consciousness into some digital form as a bid for immortality, then enhance that consciousness to expand intelligence until the subject of the process again achieves a transcendent level of awareness such that it decides to eradicate the biologically ‘lower’ human life.
Depending on the outcomes of such models as the Fermi Paradox, which suggests the probability of the existence of extraterrestrial (“alien”) civilisations, one such species could at some point cause, directly or otherwise, the destruction of humanity.
Many of the scenarios discussed are contributed to in large part by providence and the laws of chance, which cannot be determined reliably on such a large and potentially catastrophic scale even with the most sophisticated statistical analysis.
An Inevitable Apocalypse?
Thus far an apocalypse has not occurred. Of course this assertion in the style of the anthropic principle- that what is simply is because if it was any other way then it would not be possible for it to be observed- is far from satisfactory.
Simply the fact that humanity has survived this long is no assurance that it will continue to do so for a day, a month, a thousand years or longer. The random factors, both human and otherwise, seem to make any kind of preparation or anticipation a fruitless exercise.
The best that can be done is to imagine and, perhaps, to hope.