Frank Drake devised an equation to express the hypothetical number of observable civilizations in our galaxy:
N = Rs nh fl fi fc L
where N is the number of civilizations in our galaxy, expressed as the product of six factors: Rs is the rate of star formation, nh is the number of habitable worlds per star, fl is the fraction of habitable worlds on which life arises, fi is the fraction of inhabited worlds with intelligent life, fc is the fraction of intelligent life forms that produce civilizations, and L is the average lifetime of such civilizations. But there is an evident paradox. According to the Drake equation, our Universe should be populated by thousands of civilizations similar to our’s. The number of stars that appear to be orbited by Earth-like planets increases on an almost daily basis. But if that is the case, where is everybody? Why are there no signs of their existence? Why does SETI fail to produce evidence that would support the Drake equation?
In 1981, cosmologist Edward Harrison suggested a powerful self-regulating mechanism that would neatly resolve the paradox. Any civilization bent on the intensive colonization of other worlds would be driven by an expansive territorial impulse. But such an aggressive nature would be unstable in combination with the immense technological powers required for interstellar travel. Such a civilization would self-destruct long before it could reach for the stars. The unrestrained territorial drive that served biological evolution so well for millions of years becomes a severe liability for a species once it acquires powers more than sufficient for its self-destruction. The Milky Way may well contain civilizations more advanced than ours, but they must have passed through a filter of natural selection that eliminates, by war or other self-inflicted environmental catastrophes, those civilizations driven by aggressive expansion.
We propose an alternative explanation of the paradox. In the past, the Earth was populated by numerous and disjoint civilizations that thrived almost in isolation. The Sumers, the Mayas, the Incas, the Greeks, the Romans, etc., etc. If one or more of these civilizations happened to disappear, many more remained. The temporal and spatial correlation between civilizations was very limited. However, the Earth today is populated by one single globalized civilization. If this one fails, that’s it. As we know, the evolution and growth of a civilization manifests itself in an increase in complexity. The Egyptians, for example, deliberately chose not to evolve and for many centuries they haven’t advanced an inch. Such a static civilization is only possible in the presence of an extremely structured and rigid society. But any form of progress is accompanied by an increase in complexity (a mix of structure and entropy). Until critical complexity is reached. Close to criticality, a system becomes fragile and therefore vulnerable. In order to continue evolving beyond critical complexity, a civilization must find ways of overcoming the delicate phase of vulnerability in which self-inflicted destruction is the most probable form of demise. It appears – see our previous articles – that our globalized society is now arguably headed for collapse and shall reach criticality around 2040-2045. What does this mean? If we fail to move past criticality, there will be no second chance, no other civilization will take over, at least not for millenia. Clearly, the biological lifetime of our species is likely to be several million years, even if we do our worst, but as far as technological progress is concerned, that will essentially be it. Based on our complexity metric and on the Second Law of Thermodynamics we can conclude that any world populated by multiple and disjoint civilizations will always tends towards a single globalized society. It appears that globalization is inevitable and this, in turn, accelerates the increase of complexity until criticality is reached.
We argue that the self-regulating mechanism that Harrison suggests ultimately stems from critical complexity. Only a civilization which is capable of evolving beyond criticality and in the presence of overwhelmingly powerful technology, can ever hope to reach for the stars. In other words, critical complexity is the hurdle that prevents evolution beyond self-inflicted extinction. Since none of the ancient (and not so ancient) civilizations never evolved beyond critical complexity – in fact, they’re all gone – they were all pre-critical civilizations. There has never been on Earth a post-critical civilization. The only one left that has a chance of becoming a post-critical one is our’s. But what conditions must a civilization meet in order to transition beyond criticality? Essentially two. First, it must lay its hands on technology to actively manage complexity. Second, it must have enough time to employ it. The technology exists. Since 2005.