Speculation on this matter is all over the Internet and cable TV. The assumption among the particular scientists interviewed in articles and on cable programs is that it's almost a given that someday we will contact intelligent alien life. Almost all of them seem to be astronomers and physicists, not evolutionary biologists, and they base their assumptions on astronomical numbers: the odds of planets similar to ours in size, composition, temperature, atmosphere, etc., existing in our neighborhood, our galaxy, and the universe. They multiply these odds by the massive number of stars in our galaxy, and galaxies in the universe, and conclude that life, and intelligent life, is common. I think this general trend, both in the scientific community and the public, is largely wishful thinking. We don't like the thought that we might be alone, therefore we believe the opposite.
A number of assumptions are commonly made. The first is that life is likely to arise on many planets whose conditions resemble ours. But when life arose here, conditions were radically different in terms of atmospheric content, and possibly pressure, and temperature. Scientists are still largely unclear as to just what the ancient Earth was like, but it was almost certainly what we would consider very alien. If we are looking for planets resembling early Earth, we still don't know what to look for. And, we still have hardly a clue as to how life first originated. How can we assess the probability of life arising on other planets when we don't know how it arose on our own?
But even conceding the likely abundance of life in the universe, and even in our corner of the galaxy, many seem to overlook something. While preoccupied with the idea of scarcity of life in the universe, they don't consider the scarcity of intelligent life on the one planet we know life exists--our own. I don't mean this in a sarcastic social-commentary kind of way; I mean it literally. What are the odds that what we would consider intelligent life will evolve on a planet where life exists? Some talk as though they assume it's inevitable, that our form of intelligence is some logical culmination that all life inevitably evolves toward, some kind of fulfillment. I see nothing in evolution to support that assumption.
In the more than 4 billion years life has existed on our planet, many millions of species of life have come and gone, and millions of species live today. Out of all these millions of species past and present, how many 'attained' our kind of intelligence, capable of technology and long-range communication? One--us. One species, out of millions present, and many more millions past. If we're inevitable, why are we so rare? It makes more sense to think of our particular kind of intelligence as an odd quirk of evolution, like a giraffe's neck or a peacock's plumage--only we're not rare, we're unique.
Think of it this way. Imagine that at some time in the last 4 billion years an extraterrestrial intelligence arose in our part of the galaxy, the kind of intelligent life we're looking for. Now imagine that, at any time in the last 4 billion years, they had come to Earth looking for intelligent life. If they had looked here at any time from the beginning of life here over 4 billion years ago all the way through a few hundred thousand years ago--maybe a million--they would have found no 'intelligent' life, just animals. No one to talk with. If any extraterrestrial intelligences have visited Earth at any time over more than 99% of the history of life on Earth, they would have found no intelligent life. And that's on the one planet where we know life exists!
If the history of life on Earth is any indication--and it's our only indication--it seems likely that we could search the near parts of our galactic neighborhood and find thousands of planets bearing some form of life...without finding a single 'intelligent' life form.
We think if we search a few hundred systems, we'll find at least one extraterrestrial intelligence. Play the lottery much?
Not long ago, Stephen Hawking wrote his opinion on the future of mankind, stating essentially that our future is among the stars, that our best long-term chances for survival as a species involve us leaving Earth and colonizing space. Given that Hawking is one of the most brilliant astrophysicists since Einstein, his opinion carries considerable weight. But Hawking is a physicist, not an evolutionary biologist. Credentialism loses legitimacy when the expert in question ventures outside his or her field. In matters relating to physics Hawking is the man to listen to, but matters relating to evolutionary biology are better referred to scientists like Richard Dawkins. When discussing mankind's long-term future, Hawking's opinion carries no more or less weight than any other highly intelligent non-professional.
From our unclear origins as single-celled organisms to our human present, we evolved on this planet, and this planet only. Conditions have changed often over our planet's history, but mostly in slow incremental changes which evolution could keep up with. When conditions changed radically and quickly, the results were always mass extinctions. Do we think that we are so adaptable as to survive truly radical changes in environment? Think about all the conditions that will kill a human. Outside the extremely unlikely possibility of finding a planet that replicates conditions of present-day Earth almost exactly, the list of possible conditions we will encounter will all fall into the category of 'fatal to humans'. Imagine the most hostile environments on Earth: Sahara desert, Antarctica, the Himalayas. Now consider that we have yet to find a single environment outside Earth even a fraction as survivable as the most hostile environment here other than the inside of an active volcano. Can you point to any environment outside Earth which would be friendlier to human life than Antarctica or the Sahara? Humanity trying to live in space could be likened to fish leaving the water, only the jump would be far quicker, and much, much bigger.
Those of the opinion that 'our future is among the stars' imply that we are destroying our environment, 'fouling our nest' so much, that between climate change, pollution, wars, and other nasty things we're doing to our planet, we will end up making Earth unlivable, and therefore we face extinction unless we 'spread our wings and take to the stars'. But what can we do to our planet that will make conditions here anywhere near as hostile to life as the best environment we can reasonably expect to find in space? We could dump every pollutant we have into our air and water, detonate every nuclear weapon we've got, and while many people and species would die, the resulting environment would still be not nearly as deadly as anywhere else we know of. This isn't an old Star Trek episode; we can't just land on an alien world, open the hatch, and walk around breathing the air. Which surface would you rather be plunked down on suddenly: a post-apocalyptic Earth, or Venus or Mars? I'll take my chances on a post-apocalyptic Earth, thank you very much. At least here the air pressure won't crush me like a tin can on the ocean floor, or make me explode.
Think about all the things that can go wrong on any space colony. Take all the precautions taken on a base in Antarctica, for example, then multiply by a factor of ten, or a hundred, and those are the precautions that must be taken to keep the occupants of a space colony alive. So many things can go wrong when preserving a fragile artificial living space in a hostile environment, and the more hostile the outside environment, the more of these things gone wrong will prove fatal. Catastrophic airlock breach? All die. Serious problems with food or water production? All die. Long long list of problems...all die. What are the odds that any of these fatal malfunctions or events will happen in any one year? Multiply these odds by decades,centuries, millenia. Apply Murphy's Law. The long-term survival rate of any space colony will be zero, especially if there is no possibility of supply from Earth.
Our long term survival is tied with that of our own planet. If we can't make it here, we can't make it anywhere. Even in Al Gore's worst nightmare, earth is many magnitudes less inhospitable than Mars; and besides, what mistakes will we make here on earth that we won't make in a space colony?
While we can, and should, and possibly will continue to explore space, most of this exploration will likely consist of unmanned probes; and even if we manage to send human explorers into and out of the solar system, into deep space, we're not going to move there and live there. We're stuck on this island, and there is almost no possibility of anyone to talk to on any islands we could reach. Somewhere out there, somewhere in the universe, there almost certainly are others like us, but we'll never know they're there, and they'll never know we're here. We are, effectively, alone.
