Humanity is just a tiny spark. If we survive the next few decades and successfully develop superintelligence, that spark will grow into a tremendous fire on the scale of a supernova. If we fall prey to existential risk, that spark will be forever extinguished.
Our present culture, accomplishments, and intelligence are little in comparison to what we have the potential to become by the end of this century. We have the potential to become so radically intelligent that our current selves are mere insects by comparison. This doesn't mean we should hate or belittle ourselves, just realize that our greatest potential lies in our future as a civilization rather than our present.
The potential for this superlative transformation rests on three simple precepts: that radically greater-than-human intelligences are physically possible, that the speed cognitive activity is dictated by the speed of the underlying processing elements, and that intelligence can exist on a substrate other than proteinaceous neurons. I'll briefly address these three.
Is greater-than-human intelligence possible? We have no physical evidence for this, because human beings are the only form of intelligence of which we are aware. However, wouldn't it be incredibly odd if the first species on Earth to display truly general intelligence also happened to possess the highest possible class of that intelligence? Wouldn't it be odd if genetic engineering, or brain-computer interfacing, and artificial intelligence all contributed nothing to improving intelligence? I'm welcome to hear arguments for why human beings are already in possession of the highest possible intelligence level that the universe permits, if you have any. If you acknowledge that greater-than-human intelligence is possible, then how much greater? Greater than humans as we are over chimps? As we are over mice? As we are over insects? As we are over a thermostat? Discard all anthropocentric pride, and take a real guess.
Is the speed and quality of cognitive activity dictated by the underlying brain? Traditional Christianity, and likely many other world religions (I don't know enough about them) strongly imply "no". They (implicitly or explicitly) teach that humans have a God-given level of intelligence and cognitive speed and that manipulating these values by more than a trivial degree is metaphysically forbidden. If these teachings are wrong, it implies that we can ultimately tweak the underlying operation of our neurons, or replace them with faster neurons, and accelerate our thinking speed, perhaps by as much as a dozen orders of magnitude, because our neurons operate relatively slowly. Recently IBM demonstrated a single-atom memory element and molecular switch. If we could port the structure of our biological intelligence to such a device, who could tell how fast we'd then think or what we could do? This is partially a trick question: we'd be able to think faster to a degree proportional to the difference in switching speed between our biological neurons and the new substrate. I.e., pretty damn fast.
Can intelligence exist on substrates other than proteinaceous neurons? As intelligence is clearly a type of information-processing, transforming and integrating sensory information into concepts and outputting actions, there seems to be little reason why not. On a planet where life hypothetically evolves out of, say, methane-based biochemistries, our proteinaceous neurons would be as foreign to them as they to us. All it takes is for there to exist a single example of non-protein-based intelligence in the entire multiverse and we'd know that such entities are hypothetically possible. Why not try building one and see?
Bruce Klein, Outreach Director for the Singularity Institute, recently asked a question as far and wide as he could: "When will AI surpass human-level intelligence?" 50% of the respondents estimated between now and 2050. This post is directed towards that group. If AI is possible before 2050, then that means that intelligence can be ported to a nonbiological substrate, and that quickly, human intelligence will be portable to that substrate as well. That unlocks the possibility of us accelerating our thinking speed, and experiencing much more in much less time. We could experience centuries of time in a single day. This helps us envision how much we have to lose if our species is snuffed out by a technological disaster in the time between now and then.
Of course, if all three of these precepts are false, then we can still do a lot of interesting things in the future, like healing all diseases, wiping out poverty, and extending our lifespans greatly. Flying cars and megastructures. But to me, the most interesting future lies in the possibility of massively boosting our intelligence and thinking speed by transferring our civilization over to new substrates, such as diamondoid nanocomputing.