The second most common mistake in science fiction is the time frame of extraterrestrial civilisations. Let's look at it this way. Some fields of science, such as astronomy and biology, are open-ended. There will always be something new to discover. Indeed, the subjects will be changing as we watch them. But when it comes to physics and chemistry, there must come a time when we will literally know everything about the basic functioning of the universe. After that, it will just be a matter of fine-tuning the technology we already produce. We will have reached a technological plateau. How long will this take? Another hundred years? Another thousand? In any case, that is the order of magnitude of the time scale.
Now let us ask a second question: how old is civilisation? It depends on what you mean by the term. Agriculture first arose at various points abut 11,000 or 12,000 years ago. However, primitive versions of it, such as the Melanesian garden economies or the Maasai cattle herding are scarcely what most people would call "civilised". The first city, Uruk arose about 6,000 years ago. Even then, the vast majority of the world's population were still hunter gatherers - as was the whole of the human race for most of its history. Homo sapiens itself is about 200,000 years old. If aliens had seen our ancestors half a million years ago, they might have declared there was no intelligent life on earth, even if some species showed promise.
A third question: how long does it take for intelligent life to evolve? For that matter, how long is a piece of string? If an asteroid hadn't wiped out the dinosaurs 65½ million years ago, they would probably still be around. They would have seen some hard times, but there was nothing which would have caused them to go extinct, and no obvious reason any of them should evolve humanlike intelligence. On the other hand, if the asteroid had arrived 50 million years earlier, it would have kicked started the age of mammals by 50 million years, but not necessarily the evolution of intelligent life. That requires a special set of environmental circumstances. The chance might have been lost completely.
The fact is that there is no way of predicting when intelligent life will evolve, because life forms, like technology, advance faster as they become more complex. The earth is about 4,600 million years old - and there are stars, and presumably planets, even older. For the first 800 million years it was completely lifeless. After that, for the majority of its history, life was restricted to tiny, even microscopic forms. It was only about 600 million years ago that simple, multicellular organisms of any size appear in the fossil record.
In the evolution of intelligent life, let us assume that no planet can be more than 100 million years "behind" us or "ahead of" us. This, I am sure, is a gross underestimate. Let us also assume that it requires 10,000 years of civilisation before a technological plateau is reached. Of that, 6,000 years has already passed on earth, and we need another 4,000 years to reach it.
That means that, when we finally head off into the stars, half the living planets will be at an earlier stage than ours. Some of them will be stuck in the age of reptiles 100 million years ago. Some others will have primitive intelligent life forms such as evolved half a million years ago on earth. A quick calculation will reveal that they will form just half of one percent of the total. If we think of those civilisations comparable to those which have arisen in the last 6,000 years on earth, they will be present in only 0.0006% of cases.
Of course, that's just the half which are "behind" us. What would we find in the other half? Well, we wouldn't find them; they'd find us. If UFOs are what we think they are, they already have. Half the living planets in the galaxy will be occupied by civilisations more advanced than ours. Of these, all but 0.0004% will have already reached the technological plateau. And that's putting it mildly. It assumes that they all stay on their own planets. It is far more likely that they will colonise other planets before we reach them. Have no doubt about it: any intelligent life forms we encounter out there will be far, far more advanced than us, usually by millions of years.
This, you might note, is the reverse of what is portrayed in much of science fiction, especially the "space opera" type. Look at Star Trek. They were regularly encountering civilisations with technologies only 100 years or so in advance of ours - or 100 years behind us. That's not how it's going to be. The Vulcans and the Romulans would have possessed technologies which would make our science look like children's toys. We might meet a few species still running around clad in fur and throwing spears, but not very many. We are the babies of the galaxy. The others out there are probably watching us as something special: the first new civilisation to come along in a long time.
There is one more objection people might make: what if the more advanced civilisations have become extinct? That would simply mean more space for those which did not go extinct to expand into - because it is highly unlikely that every single one would go extinct.
But it might be more germane to ask exactly what could cause the extinction of an advanced civilisation, especially one which has reached the technological plateau? It is natural that these doomsday scenarios would proliferate during the second half of last century, when we lived under the threat of nuclear war, and when societies awoke to the prospect of ecological dangers. But consider it cold-bloodedly. If a nuclear war had taken place a few decades ago, it would certainly have devastated the Northern Hemisphere. A lot would depend on whether China took part in it. The economies of the rest of the world would have collapsed. Some backward societies, such as Africa, would probably have reverted to barbarism. But the human race would not have become extinct. And in isolated areas, such as New Zealand, civilisation would still have continued, as the seeds of a new civilisation. So the doomsayers would have to assume that every time civilisation made a comeback, it would destroy itself again. That's a pretty big assumption - especially if it applied to every intelligent species in the galaxy. After all, we missed it the first time round!
What about ecological collapse? Global warming would not destroy civilisation, let alone humanity. No, there is no need to "deny" the science. The worst case scenario is that the situation would become so dire that, eventually, the world would have to stop everything and fix it up - just as we did during the two World Wars. This is the fatal flaw of all the eco-apocalyptic scenarios: economics and sheer inconvenience will cut in long before total destruction.
Anything else? If another asteroid such as destroyed the dinosaurs were to have struck 100 years ago, it well might have wiped out the human race. But if it were to approach next year, we would see it coming, and at least take action to permit a nucleus of us to survive. If we saw it coming 100 years from now, we would be able to intercept it. Besides, it's not as if such disasters are a regular occurrence. The last one happened 65½ million years ago, and it appears to have been the only one.
No. Take my word for it: once high civilisations arise, they will be around for millions of years, if not forever. And they're the ones we are going to encounter.
The next chapter will be Interplanetary Hybrids.
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