If humanity remains a single planet species, our extinction is all but assured—there are so many ways the world could end. The mundane self-inflicted apocalypses include such things as war and environmental devastation. There are also more exotic dooms suitable for speculative science fiction, such as a robot apocalypse or a bioengineered plague. And, of course, there is the classic big rock from space scenario. While we will certainly bring our problems with us into space, getting off world would dramatically increase our chances of survival as a species.
While species do endeavor to survive, there is the moral question of whether or not we should do so. While I can easily imagine humanity reaching a state where it would be best if we did not continue, I think that our existence generates more positive value than negative value—thus providing the foundation for a utilitarian argument for our continued existence and endeavors to survive. This approach can also be countered on utilitarian grounds by contending that the evil we do outweighs the good, thus showing that the universe would be morally better without us. But, for the sake of the discussion that follows, I will assume that we should (or at least will) endeavor to survive.
Since getting off world is an excellent way of improving our survival odds, it is somewhat ironic that we are poorly suited for survival in space and on other worlds such as Mars. Obviously enough, naked exposure to the void would prove fatal very quickly; but even with technological protection our species copes poorly with the challenges of space travel—even those presented by the very short trip to our own moon. We would do somewhat better on other planets or on moons; but these also present significant survival challenges.
While there are many challenges, there are some of special concern. These include the danger presented by radiation, the health impact of living in gravity significantly different from earth, the resource (food, water and air) challenge, and (for space travel) the time problem. Any and all of these can prove to be fatal and must be addressed if humanity is to expand beyond earth.
Our current approach is to use our technology to recreate as closely as possible our home environment. For example, our manned space vessels are designed to provide some degree of radiation shielding, they are filled with air and are stocked with food and water. One advantage of this approach is that it does not require any modification to humans; we simply recreate our home in space or on another planet. There are, of course, many problems with this approach. One is that our technology is still very limited and cannot properly address some challenges. For example, while artificial gravity is standard in science fiction, we currently rely on rather ineffective means of addressing the gravity problem. As another example, while we know how to block radiation, there is the challenge of being able to do this effectively on the journey from earth to Mars. A second problem is that recreating our home environment can be difficult and costly. But, it can be worth the cost to allow unmodified humans to survive in space or on other worlds. This approach points towards a Star Trek style future: normal humans operating within a bubble of technology. There are, however, alternatives.
Another approach is also based in technology, but aims at either modifying humans or replacing them entirely. There are two main paths here. One is that of machine technology in which humans are augmented in order to endure conditions that differ radically from that of earth. The scanners of Cordwainer Smith’s “Scanners Live in Vain” are one example of this—they are modified and have implants to enable them to survive the challenges of operating interstellar vessels. Another example is Man Plus, Frederik Pohl’s novel about a human transformed into a cyborg in order to survive on Mars. The ultimate end of this path is the complete replacement of humans by intelligent machines, machines designed to match their environments and free of human vulnerabilities and short life spans.
The other is the path of biological technology. On this path, humans are modified biologically in order to better cope with non-earth environments. These modifications would presumably start fairly modestly, such as genetic modifications to make humans more resistant to radiation damage and better adapted to lower gravity. As science progressed, the modifications could become far more radical, with a complete re-engineering of humans to make them ideally match their new environments. This path, unnaturally enough, would lead to the complete replacement of humans with new species.
These approaches do have advantages. While there would be an initial cost in modifying humans to better fit their new environments, the better the adaptations, the less need there would be to recreate earth-like conditions. This could presumably result in considerable cost-savings and there is also the fact that the efficiency and comfort of the modified humans would be greater the better they matched their new environments. There are, however, the usual ethical concerns about such modifications.
Replacing homo sapiens with intelligent machines or customized organisms would also have a high initial startup cost, but these beings would presumably be far more effective than humans in the new environments. For example, an intelligent machine would be more resistant to radiation, could sustain itself with solar power, and could be effectively immortal as long as it is repaired. Such a being would be ideal to crew (or be) a deep space mission vessel. As another example, custom created organisms or fully converted humans could ideally match an environment, living and working in radical conditions as easily as standard humans work on earth. Clifford D. Simak’s “Desertion” discusses such an approach; albeit one that has unexpected results on Jupiter.
In addition to the usual moral concerns about such things, there is also the concern that such creations would not preserve the human race. On the one hand, it is obvious that such beings would not be homo sapiens. If the entire species was converted or gradually phased out in favor of the new beings, that would be the end of the species—the biological human race would be no more. The voice of humanity would fall silent. On the other hand, it could be argued that the transition could suffice to preserve the identity of the species—a likely way to argue this would be to re-purpose the arguments commonly used to argue for the persistence of personal identity across time. It could also be argued that while the biological species homo sapiens could cease to be, the identity of humanity is not set by biology but by things such as values and culture. As such, if our replacements retained the relevant connection to human culture and values (they sing human songs and remember the old, old places where once we walked), they would still be human—although not homo-sapiens.