Mankind was born on Earth. It was never meant to die here. - Interstellar
The human species was not meant to die on Earth. This claim can be taken in different ways. At the first mention of grand purpose and meaning, the human mind tends to fly to cosmic beings and supernatural creators. But this claim can be understood without recourse to either metaphor or metaphysics. All that is needed to fully understand this claim is an understanding of the kinds of beings we find ourselves as. That is, we can understand where we are going and, indeed, where we ought to go, by understanding where we are and where we've come from.
We are a peculiar species because we are peculiar kinds of creators. Other species create things (spiders, beavers, etc.) so what is peculiar about our mode of creativity? There are several ways in which our creative capacities are unique, but here I will focus on the one I believe is most general and of broadest philosophical import. We are the only species who augment our creative capacity with our creations. We create and then use our creations to enhance our creative capacities. That is, we are the only species who make creative progress.
A spider builds a web and its work is finished. A beaver constructs a dam and moves on with its life. A human forges a sword to protect himself and then notices this sharp metal is useful for cutting wood, turning soil, etc. and then, half by luck and half by ingenuity, notices that when this metal is rubbed and struck in different ways, different types of pleasing sounds can be produced. The human creates and then uses what was created to keep creating. Further, human history, especially the last couple of centuries, has revealed that once this capacity of self-augmenting creativity reaches a certain stage of development, it explodes into a landscape of creative possibility as diverse and complex as anything else in the known universe. Recent human history has revealed, it seems, that we are not merely creators of parochial, locally useful tools, but are general creators. That is, we can create technology of virtually infinite variety that is universally useful and our creative capacities seem limited by nothing other than time and the laws of physics.
Part of what a spider is is a web-builder. Part of what a beaver is is a dam-builder. Part of what a human is is a general creator. This means, however, that what we are is still an open question, or, better, that what we are is essentially, that is, will always be, an open question. The fact that we are general creators seems clear and is an important insight, but what our creative capacities are capable of is still obviously an unanswered question. Again, it may be that it is in principle unanswerable, that every time we make a new creative breakthrough new vistas open up before us. The faster we fly forward the faster the horizon races away.
All of this implies, of course, that engineering projects are not of mere practical import, but relate to questions of the meaning and purpose of human existence. The question of whether we can build the requisite technology to colonize Mars, for example, is not just of practical or economic import, but bears on the most basic of questions, "What are we?"
Despite the fact that we have reason to believe that the question of the full capabilities of our creative capacities will always remain an open question (if you find this claim too strong, it is still certainly the case that we are nowhere near our creative limits) and that our identity and nature will therefore always remain an open question, the more we create, the more detailed our picture of ourselves becomes. We know much more now about the kinds of beings we are than humans did 2000 years ago, or 1000 years ago, or 100 years ago, or even 10 years ago. We know, for example that we are a kind of being that is capable of leaving its home planet and reaching other heavenly bodies. (Armstrong's first step on the moon was no mere engineering accomplishment, it was one of the most important philosophical and spiritual revelations in human history. (Perhaps of greater importance was Yuri Gagarin's first journey into space, but the same point can be made with either event.))
And this insight brings us back to our point of departure. Armstrong's step revealed that, by some immense stroke of luck, back on the prehistoric African savannah, the first humans to tell tales and sharpen stone tools had a roadmap to the stars written in their DNA. Those first humans had no idea what they were capable of, the kind of beings that they were. Only we lucky few in the last five decades or so understand this most peculiar of facts about the species homo sapiens.
The African savannah gave birth to a creature unlike any other to ever walk the face of the Earth and, as far as we currently know, unlike any creature to ever wake up in this cosmos. The Earth, one way or another, is destined to die, but this peculiar animal, this homo sapiens, is the only creature she ever gave birth to which has the ability to escape. Our species wasn't meant to die here.