Have you ever looked at a sparkling city from the top of a nearby mountain, and wondered, what alien landed here?
How long has Earth hosted life . . and yet how briefly has Earth hosted human life. We're such a rapid force of change on this planet that anyone intelligent viewing Earth from a distance would observe that an alien life form must have taken over.
Semantic similarities between humans and non-resident aliens aside, there is no chance that there is not an alien life form already out and about, exploring our galactic neighborhood, Moreover it is highly probable that they will contact this planet fairly soon, as the ever increasing sphere of our radio signature races away from Earth - the edge of it now some 100 light years away. Our transmissions have already reached a huge number of planetary systems. The earth is no longer quiet . . . our electromagnetic communications have given us away to an interested race of extraterrestrials.
Aliens will come here, and we will most likely go elsewhere. Advanced life forms like ourselves, or spores from fungi that we've liberated through a convenient set of thermonuclear explosions, will float about the galaxy, as representatives of Earth, little time capsules of highly adaptable DNA, that can survive extreme environments.
I do emphasize that it matters not whether a spore, or a human being is the vector that carries the message. The key evolution of life on this planet is DNA. All else that has evolved here is too specialized to have much of a chance in another environment.
Human evolution may only serve to carry a Noah's ark of DNA to another world. Once transported, our mission might be finished.
Spores could do it alone with just a single strand of DNA in a hardy protein coat, humans might do it in complex engineered environment similar to the International Space Station.
A snippet of DNA is all that is necessary to populate a receptive medium, or change the genes of an already existing species. Modern agricultural 'gene therapy' snips and adds genes almost at will. Commercially grown roses, for years interbred for their color, size and appearance, have lost their sense of smell. Why? Well they no longer needed to produce an odor to attract insects to move their pollen around - they had humans doing the job for them. But now science has found an easy way to restore the scent of a rose to domesticated roses.
Alien means 'strange' and once we dispense with our self-view as 'normal' we'll then admit that we are strange, not as highly evolved as we think we are, and probably overdue for a lesson on the existence of more advanced galactic brothers and sisters!
Mammals were probably viewed as alien by intelligent dinosaurs. Cro magnon was certainly seen as alien by Neanderthal (and vice-versa). Homo erectus in Europe and Asia, (the oldest skeletons are only tens of thousands of years old) were called elves, fairies, demons by our ancestors - these 'people' must have been thought of as alien indeed!
The most probable source of alien life on this planet will probably be ourselves. A giant shift in human DNA, will lead to the evolution of a new species, more advanced than we are.
By the time that population is recognized, described, and feared, it will be too late to stop it. Homo sapiens will go the way of the dinosaurs, eventually. Yet we may leave 'children'. Evolution continues.
Oh the planet will most likely last long enough . . . and we will most definitely experience a collapse in population at some point or another - that will historically be perceived as dramatic, but which might even take dozens of lifetimes. Out of that crippling environment might come our successor(s). Genetics favors it. We have the numbers to create a new species. The only scenario I think that would make this impossible would be all out nuclear war, or an extra-terrestrial body colliding with and destroying our planet, not likely but possible.
And it is always possible that the events or species that bring about our end never came from here at all. This scary scenario is one we have to consider particularly if we live on, peaceably increasing our technological abilities, and, our ability to refine raw materials, as well as our ability to live amongst ourselves.
A classic adaptive situation: nuclear winter descends on the planet, but one not so fierce as to eliminate all life. This creates a number of possible pathways to survival. Being able to live with less food is one, able to survive radioactive food is another, able to manipulate technology in a world of spare parts left by broken economies, and technological waste.
Similarly if no major crisis event hits us, we are certainly likely to continue to evolve physically, emotionally, and intellectually.
a) towards vegetarianism,
b) become smaller physically, and use less energy.
c) learn to exploit the sun's energy more efficiently and
d) learn to self-govern ourselves, and the ecology of our planet.
Assuming we do these things well, our lease on Planet Earth could go on for quite a long time! But in that event the attractiveness of us, our planet, and our piles of refined metals, may become too attractive to alien life forms to pass up.
In other words, prosperity may bring us to the most cataclysmic collapse of all, or the kind of scenarios sketched by H.G.Wells.
Big towers when they fall, fall hard. Same with stars. The big ones explode like flashbulbs in middle of galaxies. . lighting everything around them. A star 27% larger than the sun can perish in a few weeks through a supernova collapse. Little stars, such as our own, and smaller. . . live on, shriveling as they grow old. . . giving off less and less energy. They are the old folks of galactic time, rocking for billions of years, while the young hotshots grow big, wealthy, and then blow up.
If a major crisis occurs, caused by man, or an outside force, cannibalism and vampires may indeed become a norm of survival for certain groups.
Vampirism has started! We give blood to restore strength! We fertilize 'in vitro' to bear young. Our hospitals are labs for extracting bodily fluids and moving them along to those that need them most.
We may indeed go 'abroad' for precious bodily fluids, proteins, i.e. sustenance, or, others may come here for the same. Or others may come here for the same reason.
All that eat, are eaten.
