Ours will not be the last human civilization. This presumed fact is both optimistic and pessimistic and should inspire equal parts dread and hope.
On the down side, inherent in the idea is that our civilization will, in fact, end. At some point, the world and cultures we have created will cease to be and very likely be forgotten for all time. How this will occur is a mystery, as is when, but there are many potential ends awaiting us or our descendents. We might, for example, simply fade away — no catastrophe, no great revelation, just the irresistible force of time’s arrow withering the body of our civilization as surely as it withers all things. Even mountains crumble under its power; what makes us believe we can outlast it? In this possible end, we are obscured by our own descendents. Like the dinosaurs becoming the birds, one day what we are will have evolved out of existence and a new thing will stand in our place, only a vague semblance of us. Of course, the end for our civilization might come hard and fast, instigated by an apocalyptic event like an asteroid collision or mega-eruption. In this case, the change and challenges wrought by this catastrophe would be too much for our civilization to accommodate or adapt to and collapse would come like a bleak dawn. Not so long ago, it was not difficult to imagine doom by our own hands, by the very tools that have made our civilization possible. We have built weapons of war that dwarf all weapons ever created put together. Even our plowshares have the potential to destroy us as we manipulate forces we do not fully comprehend and unleash them in hopes of enriching our lives and expanding our civilization.
No matter what the end, two things are near certainties: it will come, and some people will survive. Perhaps they will live in fortified bunkers beneath the surface of the earth. Perhaps they will be the people far removed from civilization as we know it now. Perhaps it will be a tiny, isolated population or perhaps a smattering of enclaves will endure the world over, none large enough to continue civilization alone. A force that could completely wipe out the human race is almost incomprehensible. Even the great mass extinctions of the past took centuries or millenia to do their grim work, so though our civilization is surely doomed our species will very likely thrive.
And herein lies the hope. Human are by their nature social and creative. Those two aspects virtually guarantee that even the smallest viable population eeking out an existence in the post-apocalyptic wilderness will create culture. With that culture will come diversity of ideas and expansion. With diversity of ideas and expansion will come trade. Just as our ancestors did after the apocalyptic era of the ice age, at the end of the next apocalyptic age our survivors will create civilization anew. Perhaps they will not be forced to start from scratch as our ancestors did; perhaps some remnant of knowledge will remain so they have a leg up. Perhaps we will be wise enough now to leave our descendents knowledge and skills they can access to make the rise to civilization easier and faster. Or perhaps it will take many more thousands of years than it did our ancestors. Perhaps our descendents will have genetic memory of the collapse of civilization and fear concrete towers and weapons that rend the sky and purposefully avoid building a civilization of their own. Even so, no such fear could last forever or infect all future people. Inevitably, one tribe or nation would rise to prominence and civilization would rise again. It is even possible that human civilization will not be reborn on Earth but another world. Should our civilization last long enough and reach high enough, we may spread among the worlds of our solar system or beyond and be reborn there.
Whatever civilization rises from the ashes of our own, it, too, is doomed. Its own end will loom before it, and also the rise of the civilization that follows it. How long can this cycle last? How many deaths and rebirths can human civilization endure before it either reaches Nirvana or is consumed into the Void? What would the civilization with no end look like? Or the one with no hope?
Finally, one other question emerges: are we truly the first? Our civilization has existed ten thousand years, from the first walled towns of the Middle East, through the millenia long lives of Egypt and China, through to the relatively short lived but unquestionably powerful modern Western civilization we have. A continuous line of people and knowledge can be traced from the first sowed fields to the Mars rovers. I presume above, and our anthropologists and archeologists and historians believe too, that we are the first such human civilization on earth. This, despite somewhere on the order of one hundred thousand years — ten lifetimes of our civilization — of mist shrouded time of human existence. If some civilization had risen before ours took root in the Levant, would we know of it? Would its artifacts or structures survive the grinding force of the glacial advance and retreat? Would we have any genetic memory of its language, art or religion? And if not, how can we know we are the first?