Since I think I have a fair chance of living long enough to see the defeat of aging, it follows that I expect to live long enough to see many momentous scientific and technological developments. Does one such event stand out? Yes and no.
You don't have to be a futurophile, these days, to have heard of "the Singularity". What was once viewed as an oversimplistic extrapolation has now become mainstream: it is almost heterodox in technologically sophisticated circles not to take the view that technological progress will accelerate within the next few decades to a rate that, if not actually infinite, will so far exceed our imagination that it is fruitless to attempt to predict what life will be like thereafter.
Which technologies will dominate this march? Surveying the torrent of literature on this topic, we can with reasonable confidence identify three major areas: software, hardware and wetware. Artificial intelligence researchers will, numerous experts attest, probably build systems that are "recursively self-improving"—that understand their own workings well enough to design improvements to themselves, thereby bootstrapping to a state of ever more unimaginable intellectual performance.
On the hardware side, it is now widely accepted as technically feasible to build structures in which every atom is exactly where we wish it to be. The positioning of each atom will be painstaking, so one might view this as of purely academic interest—if not for the prospect of machines that can build copies of themselves. Such "assemblers" have yet to be completely designed, let alone built, but cellular automata research indicates that the smallest possible assembler is probably quite simple and small. The advent of such devices would rather thoroughly remove the barrier to practicability that arises from the time it takes to place each atom: exponentially accelerating parallelism is not to be sneezed at.
And finally, when it comes to biology, the development of regenerative medicine to a level of comprehensiveness that can give a few extra decades of healthy life to those who are already in middle age will herald a similarly accelerating sequence of refinements—not necessarily accelerating in terms of the rate at which such therapies are improved, but in the rate at which they diminish our risk of succumbing to aging at any age, as I've described using the concept of "longevity escape velocity".
I don't single out one of these areas as dominant. They're all likely to happen, but all have some way to go before their tipping point, so the timeframe for their emergence is highly speculative. Moreover, each of them will hasten the others: superintelligent computers will advance all technological development, molecular machines will surpass enzymes in their medical versatility, and the defeat of our oldest and most implacable foe (aging) will raise our sights to the point where we will pursue other transformative technologies seriously as a society, rather than leaving them to a few rare visionaries. Thus, any of the three—if they don't just wipe us all out, but unlike Martin Rees I personally think that is unlikely—could be "the one".
Or... none of them. And this is where I return to the Singularity. I'll get to human nature soon, fear not.
When I discuss longevity escape velocity, I am fond of highlighting the history of aviation. It took centuries for the designs of da Vinci (who was arguably not even the first) to evolve far enough to become actually functional, and many confident and smart engineers were proven wrong in the meantime. But once the decisive breakthrough was made, progress was rapid and smooth. I claim that this exemplifies a very general difference between fundamental breakthroughs (unpredictable) and incremental refinements (remarkably predictable).
But to make my aviation analogy stick, I of course need to explain the dramatic lack of progress in the past 40 years (since Concorde). Where are our flying cars? My answer is clear: we haven't developed them because we couldn't be bothered, an obstacle that is not likely to occur when it comes to postponing aging. Progress only accelerates while provided with impetus from human motivation. Whether it's national pride, personal greed, or humanitarian concern, something—someone—has to be the engine room.
Which brings me, at last, to human nature. The transformative technologies I have mentioned will, in my view, probably all arrive within the next few decades—a timeframe that I personally expect to see. And we will use them, directly or indirectly, to address all the other slings and arrows that humanity is heir to: biotechnology to combat aging will also combat infections, molecular manufacturing to build unprecedentedly powerful machines will also be able to perform geoengineering and prevent hurricanes and earthquakes and global warming, and superintelligent computers will orchestrate these and other technologies to protect us even from cosmic threats such as asteroids—even, in relatively short order, nearby supernovae. (Seriously.) Moreover, we will use these technologies to address any irritations of which we are not yet even aware, but which grow on us as today's burdens are lifted from our shoulders. Where will it all end?
You may ask why it should end at all—but it will. It is reasonable to conclude, based on the above, that there will come a time when all avenues of technology will, roughly simultaneously, reach the point seen today with aviation: where we are simply not motivated to explore further sophistication in our technology, but prefer to focus on enriching our and each other's lives using the technology that already exists. Progress will still occur, but fitfully and at a decelerating rather than accelerating rate. Humanity will at that point be in a state of complete satisfaction with its condition: complete identity with its deepest goals. Human nature will at last be revealed.