When I first learned that the human body was made up of trillions of cells I was fascinated. These cells are almost like small organisms themselves - they grow, reproduce, consume and respond just as the organism itself does. It's almost as if the human body is a colony, not just an individual. In fact, it seems very likely that the first multicellular organisms were actually colonies of individuals which stuck together and began to evolve as a group, not just as individuals.
Another fascinating fact that I learned recently is that there are more bacterial cells than human cells in a human body - though they are much smaller they are about 10 times more numerous. It's sort of like how we keep animals of different species like cows and chickens in our macroscopic communities.
Even our human cells aren't "pure human" - they contain mitochondria which have their own DNA and almost certainly evolved from a separate line if you go back far enough in history. It's almost like life is fractal (though the self-similarity doesn't descend infinitely).
That makes me wonder if colonies act as individuals on a much larger scale. If we colonise the universe could we end up with societies that are complex enough to have an awareness of their own? Could we ever, as individuals, become aware of this awareness? Presumably (because of the speed of light) such awareness would be much slower than ours and generations could be born and die in the time it takes for a single thought to happen in on the "higher level". However, because we (unlike our cells) are intelligent beings, we could presumably read the writings that such a being had made over the course of history. Such a being would be a God, in a sense, as it would transcend us, but wouldn't necessarily be omnipotent, omniscient or kind, and certainly wouldn't have created the universe.
"Even our human cells aren't "pure human" - they contain mitochondria which have their own DNA and almost certainly evolved from a separate line if you go back far enough in history. It's almost like life is fractal (though the self-similarity doesn't descend infinitely)."
Not only are our human cell not "pure human" in that they contain mitochondria with it's own separate DNA lineage (which as you point out started as a separate symbiotic organism within early bacteria), we actually have the remnants of viruses which infected the germ cells of our forefathers (and foremothers for that mater). These ancestors were infected with a virus, which also infected their germ cells (sperm and eggs), and though they successfully fought off the invading virus fragments were left in their germ cell's DNA which passed to their offspring. Geneticists can look at modern human nuclear DNA and see fragments of known viruses. This of course happened in other animals (and plants as well) and has undoubtedly played a role in evolution.
Fascinating stuff! Life is so messy - it seems like whenever we try to figure out some kind of rule about it, we find an exception somewhere.