Any human civilization that eventually is built on another world, or built in an artificial environment not on the surface of any world, will be unprecedented in the history of human civilization. Everything else might be the same — every detail of the institutional structure of such a civilization might be identical to some civilization on Earth — but the mere fact of its existence on a world other than Earth, or on no planet at all, would make such a civilization unprecedented in the history of human civilization.
All human civilizations to date have appeared on the surface of Earth, so that this property of terrestrial domicile, usually assumed without being explicitly formulated, characterizes all known civilizations. When a property that has characterized all civilizations to date is falsified by the appearance of some new civilization (or by some new kind of civilization), and that new civilization is nevertheless recognizable as a civilization (and is not some novel form of emergent complexity that is not civilization), I call this transcendence.
The transcendence of planetary endemism will define a new class of civilizations — human exocivilizations — and these civilizations, being derived from terrestrial civilizations, will have important historical relationships to terrestrial civilizations. What will be (or what ought to be) the relationship between human civilizations off Earth and the tradition of human civilization originating on Earth? What relationship will extraterrestrial human civilizations want to preserve with their terrestrial heritage? What will we take with us from Earth? What will we replicate on other worlds from the world we left behind? On the other hand, what traditions of terrestrial civilization will we want to expunge? What will we want to leave behind? What will we seek not to replicate of terrestrial civilizations in human exocivilization?
To these questions there are short term answers and long term answers, and these answers are different. The short term answers constitute the ordinary human range of history, so all that we would expect to see happen when multiple civilizations are in contact over historical time, and one is descended from the other, would be likely to happen. The scale would be larger than that of human history, and if both terrestrial and human exocivilizations were successful, these exchanges could endure over the longue durée, but much of this interaction could be predicted on the basis of terrestrial models.
If human exocivilizations eventually appear, they will be characterized by a number of historic firsts that will establish relationships between the heritage of terrestrial civilization and the emerging culture of human exocivilizations. For example, there will be the first Old Master painting to leave Earth and to be exhibited in a gallery on the moon or on Mars, or something similar. Portable terrestrial heritage of the kind that has repeatedly throughout history been sold, traded, looted, and stolen will move back and forth between Earth and the exocivilizations. But Earth is rich is culture and history, and the populations of human exocivilizations would want to bring a part of this culture with them, so that the primary movement of terrestrial heritage would be from Earth to the exocivilizations.
In the event of a continued viable civilization on the surface of Earth along with growing human exocivilizations elsewhere in our solar system, I expect that the process of transporting human heritage off Earth will be extremely slow and gradual. Parallel civilizations on Earth and on other worlds that remain in contact with one another, no doubt bound by relationships of cooperation, competition, and conflict, will see trade and commerce, cultural exchanges, emigration and population movement. With these interactions culture and heritage will migrate from Earth to the exocivilizations.
Individuals and families would take in their luggage personal heirlooms, many of which would be of lasting cultural significance. I have known individuals who have personally owned museum-worthy objects of cultural heritage, and I expect that this is commonplace, and would be a significant factor in the off-worlding of terrestrial heritage. And there would also be individuals who would smuggle out articles that were stolen or forbidden to be taken off Earth. Customs officials would intercept some of these illegal attempts to move cultural heritage off Earth, but not all of them. Some articles would get through. Over time, this gradual and incremental process would move a significant quantity of terrestrial heritage off Earth, and the longer that this process continued, the more human heritage would leave Earth.
Although Earth is large from a human perspective, the solar system is much larger yet, and the scale of industry that can occur off the surface of Earth is many orders of magnitude larger than the scale of industry that can occur on Earth. What this means is that, eventually, great fortunes will be created off Earth in a solar system-wide economy, and the individuals who make fortunes in human exocivilizations will want to engage in symbolic and conspicuous consumption, one form of which is the purchase art treasures, much as wealthy Americans of the Gilded Age returned to the Old World in order to buy up cultural icons and bring them back. (Hence the origins of institutions like the Getty Museum.)
This gradual process of off-worlding human heritage would eventually result in a small but substantial number of objects of artistic and historical importance being preserved away from Earth. If this process were to continue as long as Earth remains habitable for a human civilization, more objects of distinctively human value would move off Earth, with the process accelerating as the end of human habitability of Earth loomed nearer. And as the viability of civilizations on Earth neared their end, we come into consideration of the long term answers to the relationship between terrestrial civilization and human exocivilization.
In the case of some artifacts, there would be a question as to whether an attempt to preserve them in situ, on Earth, or to move them off planet for their own protection, would be preferable. For example, the iconic cities of Earth are dependent upon particular geological and climatological conditions that will not obtain over the longue durée. A city like Venice, for example, is extremely vulnerable. A rise in sea level of a few feet would leave the city underwater. Assuming a civilization had the technology and the resources, would it be better to attempt to preserve Venice in situ, perhaps by raising the entire city to the appropriate elevation (much as the Abu Simbel temples were dismantled and reassembled to save it from the rising waters of the Aswan High dam), or would it be better to take the entire city and move it off Earth to a stable geological location where water could artificially be maintained at a particular level?
What will happen to Venice in the not-too-distant future will happen to all terrestrial cities sooner or later over geological time. Earth is a geologically active planet, and that means that any city on a coastline will be subject to the forces that have reshaped coastlines over Earth’s history. The cities that eventually will be built on Mars will not be subject to earthquakes and plate tectonic movements, and so will be stable for a far longer period of time than any city on Earth. Major monuments threatened on Earth could be moved to Mars, where they would likely be safe for millions of years.
Terrestrial civilization would not likely lightly give up its treasures and its heritage, even when these are threatened by terrestrial conditions. Without large-scale cooperation in moving terrestrial monuments to safer locations off Earth, these monuments are likely to experience a much higher rate of attrition than easily portable objects of historical value. If human beings in human exocivilizations feel the tug of longing for what they have left behind on Earth, there is a good chance that they will build close replicas of what has been left behind. Just as we possess many ancient Greek statues only in the form of Roman copies, we may someday possess terrestrial monuments only in the form of Lunar and Martian copies.
Terrestrial places might be recreated on other worlds (or, again, on no world at all, in an artificial environment, in addition to being virtually preserved data bases) in a grand gesture of historical reconstruction. And there might be other surprising ways of preserving our terrestrial heritage, such as building monumental projects that were never realized on Earth. For example, some future civilization might choose to build Étienne-Louis Boullée’s design for an enormous cenotaph commemorating Isaac Newton or Antonio Gaudí’s design for a skyscraper hotel in New York City. Cities imagined on Earth but never built — Frank Lloyd Wright’s Broadacre City or Antonio Sant’Elia’s Città Nuova, for exampleo — or even cities imagined in film or video games, could be actually constructed and inhabited by real human beings (if anyone wanted to live in some of these dystopian settings).
Entire cities of a particular vintage might be recreated, as open-air museums attempt to preserve the architectural heritage of past human civilization today. We will want — or, at least, some of us will want — to preserve some of this history as well. And, indeed, with the resources of human exocivilizations, the space and the funding necessary to do this on a grand scale would be available. For example, entire artificial environments might be created as open-air museums devoted to some particular tradition or period in Earth’s history. Some individuals would probably elect to live under these conditions, whether for scholarly reasons, or simply because they prefer this life, which would make the tradition come alive in a way that would be of great interest to visitors. Such recreations of the terrestrial past away from Earth would likely become tourist attractions, unless they were specifically constituted as an experiment, so that outside influence was to be kept to a minimum.
Visiting an experimental reconstruction of Earth’s past would be something like the experience portrayed in the film and later television series WestWorld, where visitors dressed the part and sought to fit in, in order to experience this reconstructed past authentically. By the time when it is possible to do this away from Earth, no doubt the technology to build robots indistinguishable from human beings would also be available, so that immersive experiences created for the purposes of entertainment, again, as in the television series, would be possible. While it would be easy to dismiss this sort of thing as a mere distraction, or a vulgar imitation, an immersive experience of history someday may be the most effective tool for teaching history in a way that is more compelling than any academic setting. The importance of this should not be glossed over. It may fundamentally change our relationship to the past, and how we understand ourselves as a consequence of the historical process.
In the event of some catastrophic disruption in human civilization (which would no doubt affect both terrestrial civilizations and human exocivilizations, regardless of which was primarily affected), if terrestrial civilization failed rapidly, there would be rapid departure of objects of human significance, and a kind of triage would take place by which the most valuable items were spirited away, whether legally or illegally. With a rapid failure of terrestrial civilization, cities would be abandoned, their art treasures looted, and eventually the abandoned cities would return to nature, to be swallowed up by the tides, the sands, the jungles, or covered over with layers of sediment. This is occurred many times in terrestrial history, and these forgotten and buried remains give contemporary archaeologists something to dig up in investigating Earth’s past. One can, in this way, easily imagine a future in which Earth is largely abandoned in a disruptive event, but hundreds or thousands of years later scientists and archaeologists return to Earth to excavate the major sites.
One can even stretch one’s imagination into the future when terrestrial civilizations have collapsed and human exocivilizations return to Earth on expeditions to recover terrestrial heritage in a kind of salvage archaeology, so that the crown jewels of Earth’s civilizations can be preserved in safety for future generations — and not on Earth. Libraries of ancient books may be collected, great sculptures may be carefully crated and lifted off Earth, the contents of defunct museums may be swept up and transferred to other worlds. It is entertaining to imagine the logistics of crating the Nike of Samothrace and carefully lifting it out of the ruined roof of the Louvre and into the belly of a waiting spacecraft, to be whisked away from Earth.
These long term answers to the question of the relationship between Earth and its daughter exocivilizations lie beyond the ordinary horizon of human experience, and they force us to address questions of planetary scale and even questions of cosmological scale. Even under ideal circumstances, even if we do everything right, the Earth will eventually become uninhabitable. When all the oceans have been boiled away and our pale blue dot is no longer blue, but brown and gray, humanity or the heirs of humanity will either be extinct or living elsewhere. But long before Earth is uninhabitable, the surface of Earth will rearrange itself so completely that everything that human beings have built, every trace of our culture on Earth, will be destroyed as coastlines change, mountains rise and are worn away, and seas rise and fall.
These are not existential risks, but rather existential certainties — the only reason we do not think of them as certainties is because they lie so far in the future that these eventualities seem hazy at best to us, and certainly irrelevant. I suppose most people simply assume that human beings and their artifacts will be long gone by that time. However, if one makes a habit of thinking of the far future (as I do), one must ask oneself, if civilization, or some post-civilization institution that is the result of descent with modification from contemporary civilization, manages to survive over geologically significant periods of time, what will become of the heritage of our civilization? What efforts could be made, and what efforts ought to be made, toward the conservation of our terrestrial heritage?