Donald gazed down upon the gleaming city of Newer York and the gleaming citizens that walked, rolled, or flew its gleaming streets. Long ago, or so the oldest files in his memory indicated, he had been an organic human. That human, whom Donald regarded as himself, had also gazed down upon the city, then known as New York. In those dark days, primates walked and drove the dirty streets and the only things that gleamed were puddles of urine.
Donald’s thoughts drifted to the flesh-time, when his body had been a skin-bag holding an array of organs that were always but one accident or mischance away from failure. Gazing upon his polymer outer shell and checking a report on his internal systems, he reflected on how much better things were now. Then, he faced the constant risk of death. Now he could expect to exist until the universe grew cold. Or hot. Or exploded. Or whatever it is that universe do when they die.
But he could not help be haunted by a class he had taken long ago. The professor had talked about the ship of Theseus and identity. How much of the original could be replaced before it lost identity and ceased to be? Fortunately, his mood regulation systems caught the distress and promptly corrected the problem, encrypting that file and flagging it as forgotten.
Donald returned to gazing upon the magnificent city, pleased that the flesh-time had ended during his lifetime. He did not even wonder where Donald’s bones were, that thought having been flagged as distressing long ago.
While the classic AI apocalypse ends humanity with a bang, the end might be a quiet thing—gradual replacement rather than rapid and noisy extermination. For some, this sort of quiet end could be worse: no epic battle in which humanity goes out guns ablaze and head held high in defiance. Rather, humanity would simply fade away, rather like a superfluous worker or obsolete piece of office equipment.
There are various ways such scenarios could take place. One, which occasionally appears in science fiction, is that humans decline because the creation of a robot-dependent society saps them of what it takes to remain the top species. This, interestingly enough, is similar to what some conservatives claim about government-dependence, namely that it will weaken people. Of course, the conservative claim is that such dependence will result in more breeding, rather than less—in the science fiction stories human reproduction typically slows and eventually stops. The human race quietly ends, leaving behind the machines—which might or might not create their own society.
Alternatively, the humans become so dependent on their robots that when the robots fail, they can no longer take care of themselves and thus perish. Some tales do have happier endings: a few humans survive the collapse and the human race gets another chance.
There are various ways to avoid such quiet apocalypses. One is to resist creating such a dependent society. Another option is to have a safety system against a collapse. This might involve maintaining skills that would be needed in the event of a collapse or, perhaps, having some human volunteers who live outside of the main technological society and who will be ready to keep humanity going. These certainly do provide a foundation for some potentially interesting science fiction stories.
Another, perhaps more interesting and insidious, scenario is that humans replace themselves with machines. While it has long been a stock plot device in science-fiction, there are people in the actual world who are eagerly awaiting (or even trying to bring about) the merging of humans and machines.
While the technology of today is relatively limited, the foundations of the future is being laid down. For example, prosthetic replacements are fairly crude, but it is merely a matter of time before they are as good as or better than the organic originals. As another example, work is being done on augmenting organic brains with implants for memory and skills. While these are unimpressive now, there is the promise of things to come. These might include such things as storing memories in implanted “drives” and loading skills or personalities into one’s brain.
These and other technologies point clearly towards the cyberpunk future: full replacements of organic bodies with machine bodies. Someday people with suitable insurance or funds could have their brains (and perhaps some of their glands) placed within a replacement body, one that is far more resistant to damage and the ravages of time.
The next logical step is, obviously enough, the replacement of the mortal and vulnerable brain with something better. This replacement will no doubt be a ship of Theseus scenario: as parts of the original organic brain begin to weaken and fail, they will be gradually replaced with technology. For example, parts damaged by a stroke might be replaced. Some will also elect to do more than replace damaged or failed parts—they will want augmentations added to the brain, such as improved memory or cognitive enhancements.
Since the human brain is mortal, it will fail piece by piece. Like the ship of Theseus so beloved by philosophers, eventually the original will be completely replaced. Laying aside the philosophical question of whether or not the same person will remain, there is the clear and indisputable fact that what remains will not be homo sapiens—it will not be a member of that species, because nothing organic will remain.
Should all humans undergo this transformation that will be the end of Homo sapiens—the AI apocalypse will be complete. To use a rough analogy, the machine replacements of Homo sapiens will be like the fossilization of dinosaurs: what remains has some interesting connection to the originals, but the species are extinct. One important difference is that our fossils would still be moving around and might think that they are us.
It could be replied that humanity would still remain: the machines that replaced the organic Homo sapiens would be human, just not organic humans. The obvious challenge is presenting a convincing argument that such entities would be human in a meaningful way. Perhaps inheriting the human culture, values and so on would suffice—that being human is not a matter of being a certain sort of organism. However, as noted above, they would obviously no longer be Homo sapiens—that species would have been replaced in the gradual and quiet AI apocalypse.