It’s not difficult to discover an alien creature. Take a sterile plastic tip, pass it between your gum and tooth, and put it on the microscopic slide. Among the masses of bacteria you’ll see will be many which don’t need oxygen to survive – in fact, creatures to which oxygen is a poison, which destroys them as surely as breathing in Zyklon B would you or me.
If one is a little more adventurous, one could go down to the depths of the Pacific ocean, where life clusters around geothermal vents – life which flourishes at temperatures near the boiling point of water, at pressures which would crush any of us flat as a sheet of thick paper, and at levels of mineral concentrations which would be toxic to any organism living nearer the surface. Here are giant tubeworms, which don’t even have mouths and digestive tracts, but have masses of symbiotic bacteria creating food for them.
(One might even imagine a religion for these creatures – where god lives underneath, not above, and hell is the frigid, low-pressure heights above. And one can imagine the wrath of this god, which causes tectonic shifts to close off the vents, so that everything around withers and dies.)
Then there are the tardigrades, which I’ve mentioned elsewhere – a phylum of creatures so tough that they can survive being roasted, boiled, frozen, starved for years on end, subject to hard radiation and shot into the vacuum of space without protection – all the same creature, remember.
Why do I call these creatures alien? Aren’t they of this earth?
Well, of course they are. But so what?
Let’s imagine a planet, like one of those the scientists are discovering just about every week these days in the “Goldilocks zone” orbiting other stars, which is to say, at distances where liquid water is possible and conditions may be conducive for life to develop. Now let’s imagine some – purely theoretical – life on one of those planets. If it’s a rocky planet, like earth, with liquid water, it’s got to have approximately earth-like conditions, even if particular details differ – say, it has a different mix of atmospheric gases than earth.
Most creatures which evolve under such conditions will, therefore, be fitted to life on that planet broadly like we are fitted to life on this one. While, of course, shape, size, and other physical features – dependent on the accumulation of beneficial mutations over hundreds of millions of years – will differ, an “alien” from such a world and a human could more or less coexist under the same conditions, with only minor aids, like, say, gas masks, being necessary.
So, just how is such an organism more “alien” than something which is living, literally, in your gums?
Even Hollywood hasn’t managed to come up with creatures as alien as the deep sea tubeworm. The archetypal Alien itself, which gestates inside a human body before exploding out in a shower of blood and Ellen Ripley heroics, is a pretty straightforward lift from a common Earth organism – the ichneumon wasp. Not that anyone ever accused Hollywood of having originality or imagination.
Meanwhile, of course, to an anaerobic bacterium or a deep sea tubeworm, we are the aliens. We breathe poison, live under conditions approaching vacuum, and at temperatures where any decent, honourable tubeworm would freeze in an instant. We even have mouths and eat, instead of having other organisms create food for us out of minerals in the water. How can any of these creatures not conceive of us as aliens?
The fact that earth organisms are more “alien” than most “aliens” would be raises an interesting notion. Life can adapt, apparently, to any conditions anywhere, even if said conditions would normally be considered lethal. Therefore, life ought to be a remarkably tenacious phenomenon, occupying any and all niches which it can possibly occupy.
To something, somewhere, we are all aliens. Or, in other words, none of us are.
Live long and prosper. I have spoken.