An essay for the middle of night.
In principle life will begin any place where the conditions for it are suitable, but the eventual evolution of an intelligent species, i.e., one possessing what we call would call true consciousness, is a much more complex proposition, resting as it does on an increasing number of variables at each emergent level. The number of ways life can evolve without producing an intellectually advanced species is formidable, and it is entirely possible that most life in our Universe is no more advanced than microbes. Even if it becomes established, an intelligent species may destroy itself in any number of ways; we might eventually provide our own example of how this is done. Nonetheless, we may suppose that there are in fact other civilizations which have emerged in our home galaxy. How numerous such civilizations might actually be is still a matter of considerable dispute, however. Peter D. Ward and Donald Brownlee have argued that the number of true civilizations in the Milky Way might be much lower than we commonly believe. They have come up with a formula which they believe to be the basis for a realistic estimate. They first discuss the famous Drake Equation (after astronomer Frank Drake), formulated in the 1950s:
N* x fs x fp x ne x fi x fc x fl=N
N*= stars in the Milky Way Galaxy
fs = fraction of sun-like stars
fp = fraction of stars with planets
ne = planets in a star’s habitable zone
fi = fraction of habitable planets where life does arise
fc = fraction of planets inhabited by intelligent beings
fl = percentage of a lifetime of a planet that is marked by the presence of a communicative civilization.
Based on the assumption that planets are very common, Carl Sagan and other astronomers posited at one time that the Milky Way contained 1,000,000 communicative civilizations. But Ward and Brownlee point out that planets may be less common around stars than initially believed (although a number of exoplanets have been discovered) and they also point to the complex interaction of variables on our own planet (the influence of plate tectonics, a low number of mass extinctions, the presence of a large moon) that may be necessary for the emergence of intelligent life. Their equation, therefore, looks like this:
N* x fp x fpm x ne x ng x fi x fc x fl x fm x fj x fme = N
N* = stars in the Milky Way Galaxy
fp = fraction of stars with planets
fpm = fraction of metal-rich planets
ne = planets in a star’s habitable zone
ng = stars in a galactic habitable zone
fi = fraction of habitable planets where life does arise
fc = fraction of planets with life where complex metazoans arise
fl = percentage of a lifetime of a planet that is marked by the presence of complex metazoans
fm = fraction of planets with a large moon [to stabilize the tilt of a planet’s axis and to help stabilize its atmosphere]
fj = fraction of planets with Jupiter-sized planets [ones that gravitationally attract asteroids and comets]
fme = fraction of planets with a critically low number of mass extinction events
Based on these much more rigorous criteria, Ward and Brownlee estimate that planets where communicative civilizations emerged are very rare. Even assuming that there are just a few thousand planets in the Milky Way with any advanced life might be optimistic.
In my view, to be pessimistic, there might be no more than 100 civilizations, including our own in the 100,000 light year diameter of our galaxy. A civilization on average every 1,000 light years. But multiply this figure by 125 billion or so galaxies (to use a low estimate), and there may still be more than twelve trillion civilizations in the Universe. Perhaps it’s not as lonely out there as we might fear. Even if there is only one civilization per galaxy on average, it still means that the population of the Universe may be well into the quintillions of intelligent beings.
What are they like? To say the least, the images of aliens provided by our popular culture have not, for the most part, been helpful in answering this question. Any life form must conform to certain physical boundaries, and perhaps it would be useful to confine ourselves to examining where these might lie. To begin with, extraterrestrials are probably three-dimensional (no flat aliens need apply). As Peter Atkins has pointed out, nervous systems function most efficiently in three dimensions and in particular the neuronal interconnectivity with which we associate higher order intelligence is only possible in such a configuration. It is conceivable that there are stringy intelligent beings or beings for whom depth has no meaning, but the probability of them is vanishingly small.
Next, we must assume that they are neither incredibly tiny nor breathtakingly gargantuan. Different gravities on different planets would, of course, permit a wide range of sizes among intelligent creatures, but I would guess the planets where such beings evolved are probably not characterized by Jupiter-like gravity (which would make the vertical growth of animals problematic although they could be stretched very far horizontally). Very low gravity would present difficulties as well, so such beings probably live on planets that are not radically different from terrestrial size (unless these beings have re-engineered their home worlds). We should also remember that physical laws dictate the proportions and dimensions of living things. Intelligent giants could exist elsewhere. but their structures would still be severely circumscribed by gravity. There could be enormous cloud-like beings (which has been speculated by some writers), but as Arthur C. Clarke has pointed out the speed of their nervous systems would be limited by the speed of light and in order to function effectively and intelligently their brains would have to be of a manageable (and inherently limited) size. Physical laws also restrict smallness of size. There could be very small intelligent beings, but the cells out of which they are constructed would have to be very small as well, and cells are pretty tiny as it is. If we assume that brains need large numbers of cells to develop intelligence, it would seem to rule out a race of intelligent creatures the size of a spider monkey. And yes, we should forget about worlds of intelligent creatures who live around atoms. (A wonderful discussion of such matters is found in Clarke's Profiles of the Future). Therefore, we should not expect that aliens would be many orders of size different from ourselves, although there could be a great deal of variation. (Witness the difference between our tallest humans and the smallest dwarves.)
We should probably assume that intelligent beings are not photosynthetic (and hence not plants) and thus they would need to ingest material for their metabolic processes. (Yes, we might indeed be appetizing to them.) If they do need to eat in the sense we understand it that means they must be mobile in some way. We must also assume that they have some way of manipulating the physical objects around them. If they couldn't do so, it’s hard to see how they could construct a civilization unless they were telekinetic (which I strongly doubt somehow). Dolphins and whales on our own planet are highly intelligent beings but they are not technological. Their inability to grasp and manipulate objects precludes this. (So does this mean our alien friends live on land rather the water? Not necessarily. but it might be easier for them if they did.) Therefore, extraterrestrials probably have appendages of some sort, although these could be of a startling variety of sizes, shapes, and flexibility.
They would also have to have some sort of sensory apparatuses for detecting the energies which flow and undulate around all of us. Their primary sense for navigating the physical world might not always be sight, however. As Richard Dawkins has pointed out, bats construct a sonic reality which is as vivid to them as visual reality is to us. Therefore, alien eyes might not always be as acute as ours (or even exist, for that matter). If they are of a race which evolved eyes, those eyes may be adapted to perceive different parts of the light spectrum than our own. They may be multiple in number (although two eyes are handy in the construction of a visual field which permits depth perception). Other sensory apparatuses which they may have evolved or given themselves through genetic engineering may allow them to perceive various forms of radiation, signals transmitted directly from other brains, or forms of energy the existence of which we might not suspect.
Of course, the above limits leave a lot of room for variation. What are their body chemistries? Are they carbon based, like terrestrial life forms, or are they perhaps based on silicon or some other element which bonds readily to form organic molecules? Are they based on nucleic acids of some sort? Do any of them resemble terrestrial mammals or could there be intelligent creatures which resemble Earth’s amphibians or reptilians in appearance (or even its birds, for that matter)? Is it possible that there are multiple species of intelligent, culture-possessing, symbol-manipulating beings on some of these planets? Do the beings of other worlds have lung-like structures or do they process atmospheric gases in some other way? What are their brains like? Do their brains, like ours, reflect their species' evolutionary history, and if so are these beings mixtures of instinctive emotional. and intellectual behaviors? How do their brains process and transmit language? Have any of them figured out a way to transcend physical bodies altogether and exist as pure intelligence (which strikes me as improbable, but who knows)? One thing is certain: they don’t look like us. The odds against this are so prohibitive that we needn't concern ourselves with it. Any science fiction which portrays aliens as human-like in their appearance strikes me as being particularly unimaginative.
But aside from my child-like curiosity about the possible appearance and physical features of extraterrestrial intelligent beings, there are deeper issues with which I’d like to deal. Is there a set of rules that would apply to any intelligent, consciousness-possessing, sentient being anywhere in this or any other possible Universe, rules which would arise naturally from the very nature of mind itself? I ask this not because I think we will ever encounter such beings—I consider the odds of this happening to be remote—but rather to try to connect us intellectually and emotionally to a larger reality than ourselves, and to see our moral rules in a new perspective.
We must imagine that intelligent creatures everywhere possess awareness of the impact of their actions on others and thus (in some way) have a moral and ethical sense. It’s difficult to see how they could interact with each other if they didn’t. (In that sense, an ethical system has utility. It serves as a minimal social good.) If they, like us, evolved in part through physical struggle and violence, have they learned how to overcome their violent tendencies? How do they get along with each other now in light of their own past histories? In how many ways have moral issues been resolved, and what kinds of sufferings and sacrifices were necessary to bring about these resolutions? Have others been able to achieve the precarious balance between the rights and integrity of the individual and the needs of a broader social group? Is there a universal sense of right and wrong, a sense of empathy perhaps based on phenomena similar (although obviously not identical) to the mirror neurons in our own brains?
More ominously, are there planets where the doctrine of Might-Makes-Right has triumphed to the exclusion of all other possible ethical systems? Has the utility of evil proven so alluring that there are planetary civilizations that are nightmare worlds of oppression, savagery, violence, suffering, and uninhibited cruelty? On our own planet the grim history of would-be world conquerors must give us at least some pause. The impulse toward mass murder and mass enslavement still rests in the darkest recesses of some of our fellow humans’ minds. There is at least the possibility that such horror may yet engulf us. There is a very real possibility that it has engulfed others elsewhere.
Moreover, in the course of the social evolution of other intelligent species, did they evolve belief systems that were planet-centric, ones that placed them at the center of creation, as did ours? Did their planets tend to develop several different belief systems, and if so, did their worlds undergo the agonizing religious clashes we have seen on ours? If there are indeed multiple intelligent species on these planets, how did they learn to co-exist? There may have been terrible racial wars, true inter-species conflicts that scarred the history of these worlds. How have the civilizations which may have experienced such events managed to overcome their deleterious effects?
In attempting to address such questions, we must assume, I believe, that any intelligent species anywhere in any frame of reference:
A. Is the product of some sort of organic evolution in which reproductive success was of paramount importance.
B. Is sentient in some way and to some degree, and this sentience is the product of its evolutionary inheritance.
C. Is descended from ancestors who had to figure out the rules of their planet from scratch, just as ours did, and discovered the true nature of their world haltingly, over a great period of time.
D. Has ancestors for whom survival involved certain difficulties and hardships, and for whom certain rules of conduct were indispensable.
E. Has undergone a long process of social evolution which has not always proceeded smoothly, and which may have involved a significant amount of interpersonal violence
and other upheavals.
Therefore, an ethical system anywhere in the Universe or Multiverse might rest on the following assumptions:
1. The awareness of the self. Assumption: The survival and physical well-being of the self is desirable, and hence a being has the fundamental right to acquire those things that are essential for its survival and to defend itself.
2. Emotional attachment to a kinship group. Assumption: The security and survival of a being’s family, especially its offspring, is a matter of vital concern.
3. Group Identity. Assumption: The well-being of the broader group of which a being is a member is a vital concern, in light of the group’s likely importance to the survival of the being and its in-groups.
4. Group cohesion. Assumption: Intra-group violence is generally counter-productive and something to be discouraged. Rules of conduct must therefore exist and be enforced.
5. Unregulated Group Relations. Assumption: Ordinary interaction between members of a group must rest on interpersonal trust, lest chaos and anarchy come to prevail.
There are other assumptions which could be made, of course, but to me these seem to be
the most fundamental ones, inasmuch as they are directly related to the reproductive success of the individual and the group of which it is a member.
A group somewhere in the Multiverse may take into consideration other ideas, over and above the basic assumptions, ones which encompass a much wider range of beings. A truly advanced ethical system anywhere might embrace such propositions as:
1. All sentient beings are as real as any others, and since they are sentient, have the capacity to experience both pleasure and suffering. Conversely, I am as real as any other sentient being, and I have a right to expect other intelligent beings to be cognizant of this fact and act accordingly.
2. Our sympathies must not lie entirely with our own group, our own kind of being, or our own culture. They must extend to all others. We have a right to expect reciprocity in this matter. Our empathy must extend as widely as possible as well.
3. We must never seek to deliberately impose needless suffering on any sentient being, and we must never inflict suffering on others who are innocent of any offense against us.
4. We must respect the world upon which we live, and preserve it for those who will come after us.
5. We must grant to all sentient beings the right to make of themselves what they can, within the boundaries of respect for other sentient beings.
Again, there are others, but in my view these all represent a step beyond the basic ethical principles. If a civilization embraces the doctrine of mutual respect among its members, it has genuine hopes of avoiding a future of endless brutality and the horrific reality of “the war of all against all”.
A major complication which might alter these assumptions is the possibility that the intelligent life form of some other world might be machine-based, the product of what we would call artificial intelligence. In that case, we would have to assume that such entities are the successors of organic beings. They would be the indirect product of organic evolution, a sort of secondary offshoot of it. Such machine-based intelligence would have undergone its own evolutionary path, but it might have been a very rapid one, as it has been on this planet, and the machines may in fact have aided and directed their own evolution significantly. Whether an AI entity is capable of consciousness is an issue, as we have seen, that has yet to be resolved. From an ethical standpoint, would an AI entity be a person, some one instead of some thing? And would an AI entity have any capacity for empathy or respect for the survival of others? Would such entities have goals and purpose? Would they evolve an interior emotional life, or is such a question merely the product of one human’s inability to conceive of consciousness on any basis but his own?
How many histories are taking place out there? How many wars, migrations, scientific and technological revolutions, religious movements, artistic developments, empires rising and falling have there been? How many philosophies have been generated? What explanations have the Aristotles, Lao-Tzus, Siddharthas, and Augustines of other planets come up with for the mysteries of existence? In how many civilizations is a god of some sort worshipped? lf there is in fact a single universal God, has He (or it) played out a series of huge cosmic dramas with the intelligent beings of other planets in ways similar to those believed by Jews and Christians to be taking place on this planet? (Have there been, in countless number, prophets? Messiahs? Saviors? Resurrections?) In how many ways is love expressed? Hatred? Passion? Artistic sensibility? We must imagine that somewhere, every conceivable act of which intelligent beings are capable is happening right now (in our frame of reference), from the most deeply spiritual and altruistic to the most atrociously horrible. In a sense, in various parts of the Universe or Multiverse, our entire experience is being recapitulated at any given moment. This is a reality I can't see but it overwhelms me just in its contemplation.
It may be extremely unlikely we will ever directly encounter any other intelligent, language-possessing species. But in the most general sense, we should acknowledge them as fellow perceivers of the Universe, and wish them well in their pursuit of knowledge of it. From an ethical standpoint, we must regard any extraterrestrial intelligent beings as persons. This means, if we endow persons on Earth with certain rights and considerations, that these extraterrestrials would deserve the same. We must know that even though we may never encounter them, that they are as real as we, and by virtue of that fact, deserving of our sympathies and respect. We must hope that they feel the same way. In that sense, perhaps, we might know each other after all.