Why has the earth not been colonized from outside, although any developed technological civilization should be able to diffuse through the galaxy within a few million years? Mainly two answers have been proposed:

(1) We are alone (or nearly so) because some narrows along the path towards our level of complexity make the appearance of intelligence or civilization extremely unlikely events. A whole universe (or even multiverse?) is then needed to let this possibility become realized on just one planet.

(2) Technological civilization itself is the narrows. Either it becomes selfdestructive through global ecological (or social) disaster, or it succeeds in self-organizing technological restriction. Then, mind might be a long-lived phenomenon but renounce the spatial expansion of its own physical structure.

The first answer has been favoured by Brandon Carter, Frank Tipler and many others. Carter’s probabilistic argument [1, 2] is impressive at the first glance: A crossing of the narrows must be extremely unlikely, because otherwise it would have happened much earlier; that it happened only “near the end” (at about half the life-time of the sun) appears then as a natural implication of the fact “that we are here”.

The weakness of Carter’s argument lies in the fact that many known and unknown processes on earth happen on time-scales similar to that of solar evolution. Present knowledge may not even be sufficient to exclude the possibility that the decay of some abundant radioactive nuclides was necessary before life or nervous systems could reach their present level of complexity. Similarly, the decreasing frequency of large volcanic eruptions and of collisions with interplanetary bodies might have played a role, as well as the slow shaping of Gaia’s crust and atmosphere as parts of the biosphere. Therefore, the idea that “intelligence” is likely to appear on “habitable planets” after a few billion years is still compatible with Carter’s argument.

Tipler [3] argued that “the most solid experimental fact” in this whole discussion is the absence of foreign explorers or conquerers throughout the earth’s history. In his opinion this makes the SETI project comparable to ESP-research: “Virtually any motivation we can imagine that would lead extraterrestrial intelligences to engage in interstellar radio communication with us would also motivate them to engage in interstellar travel. In particular, radio communication is colonization of other inhabited star systems by memes (idea complexes) from alien star systems. If one pposed on moral grounds colonization by genes (via interstellar travel), one would also oppose colonization by memes (via radio). Interstellar colonization either by genes or by memes necessarily implies biological evolution on an interstellar scale: The first intelligent species to originate will occupy all ecological niches available to it, a behaviour pattern adopted by all species that ever existed on the earth. …” [3]. Obviously, Tipler assumes that mind’s ecological niches would have to be found in physical space. “What have they been doing these billions of years?”, he asks – but isn’t this a childish question? Even human mind has already discovered quite different spaces for inward instead of outward expansion. And even some human minds do communicate with others without wishing to “colonize” them. Mind is a new front of evolution in the space of possibilities, not “property” of some individuals or species or cultures.

From arguments like Tipler’s we can certainly not exclude the possibility that there are intelligences around and communicate with each other. Concerning the present and future attempts of search for extraterrestrial intelligence (SETI), Jill Tarter said [4]: “It’s technology which we are trying to detect – not intelligence”. This very relevant remark leads us to the right track to answer the question “Where are they?”, even if we don’t think we are necessarily alone.

I have often argued [5] that technology itself is the narrows along the way to further mental evolution, because there is a purely logical upper limit to the speed of growth of complexity, and that so-called technological civilization surpasses that limit, thus destroying the conditions for further “creation of values”. Even worse, from the theory of creation, i.e. self-organization, there follows what I called the “devil-theorem”: In a spatially finite system with unbounded evolution the speed of innovation must increase until a global instability sets in.

Why is that so? We do have a “solid experimental fact” (just look at the present situation of the earth), but we can gain more general insight by thinking about time and complexity. To remember what complexity is, consider the number of possible “relation structures” for a set of points with one line or no line between any two of them. How many points are needed to let the number of such possible structures surpass the number of baryons in our observed universe? The answer is: 24 points! How, then, have viable structures at all been found and kept any stability for some time? How is the history of our universe and all its details being selected? This single realized line in a practically infinite-dimensional space of possibilities? It started from an extremely special global state (“big Bang”) which offered immense “fossil” resources and sinks for later self-organization. (The two main sources of free energy are “fossils of the first few minutes”: Because things were thrown apart, they stored gravitational potential energy with respect to each other, which can be re-gained in the formation of lumps, and, because expansion was initially so fast, there wasn’t time to go beyond Hydrogen and Helium, the fossil fuels in stars.) Ever since this unlikely beginning, the unavoidable fluctuations have been exploring neighbouring possibilities. Since there are so many of them, there are probably “better” ones found, more viable ones – if there is time enough to test the relevant relations between the new and the old. More viable possibilities survive by definition. A hierarchy of dissipative structures emerges, with more and more mutual adaptation, which also includes relative isolation as far as possible. The tautological principle of this Darwinian co-evolution is: “Probably, something more likely is going to happen”. This is the meaning of time, the drive behind the growth of complexity in our universe – up to the speed-limit.

Does this mean that the “better” (the more complex, which we find more valuable) arises without any value-judgement? No, the selection process is the value-judgement, and its principle is the same on the levels of physical, chemical, biological and mental evolution. One can easily see why the emerging world is hierarchical. Structures on lower levels, the viability of which has long been tested, will be used on higher levels with little modification because attempts to “improve” them must introduce many untested interactions nd, therefore, probably lead to break-down. With too many new relations (remember the 24 points!) time is not sufficient to try them out, and no viable new structures will be found, even if they might be possible. Building upon time-tested feed-back loops is more successful. Still, a crisis is unavoidable.

At any moment, there is a “front of evolution in the space of possibilities”, where innovation proceeds fastest. This speed is itself an “evolutionary success” and is likely to grow until feed-back with the whole becomes insufficient. Then, this front collapses, but evolution goes on with whatever diversity is left. Of course, we cannot formulate a general system-theoretical argument which would allow us to call certain developments “safe” in the sense that they will not destroy there own roots. However, even with the absurd assumption that the front might succeed in complete emancipation from its roots and the whole, a logical limit to the speed of creation of values is self-evident: The level of complexity reached has to be “relearned by each generation”. Thus, the critical speed is roughly defined by “essential change within the life-time of the individual structures at the front”. If the (r)evolutionary process of fluctuation and selection gropes its way into the space of possibilities faster than that, the leading sub-systems cannot even take into account their own complex value. Self-organization of global simplicity sets in and increases the speed of “wrong” value-judgements further. Within a few generations of the leading sub-structures they start destroying themselves and the viability of the whole system from which they evolved.

As I wrote elsewhere [6]: “ … Evolution itself defines and creates a critical time-scale, which it then necessarily tries to surpass. But thereby it must destroy its own logical preconditions. The leading figures at the front of evolution don’t give themselves enough time to judge values in the process of exploring the neighbourhood in the space of possibilities. Of course, the tautology remains valid that “more likely things will probably be realized” via the accidental fluctuations (including their more recent form of appearance, called planning) – but with a lack of time for selective adaptation, i.e. adaptive selection, the more likely is no longer a growth of complexity but rather its decomposition. In a very sophisticated way, the entropy law seems to have conquered the Earth, an open dissipative system in which we thought it wouldn’t be valid. While everybody was still worrying and quarreling about the resources, we have been filling up and blocking the sinks …”

This kind of instability is quite similar to the “success” of a fast-growing water-lily on a pond, or of a cancer-cell in an individual organism. The characteristic difference, however, lies in the “globality”. If the system is isolated or spatially finite in the sense that the time-scale for communication with the outside is long compared to the time-scale of the instability, no revival from “outside ponds” and no survival of “outside individuals” will stop or heal the local disaster. A black hole will remain, or scorched earth.

If evolution doesn’t stop due to external influences, this onset of global instability is probably unavoidable. Growth of evolutionary speed itself seems to be an evolutionary success as long as the errors can be pushed to the “borders” – i.e. until the global scale has been reached. This acceleration must certainly take place when evolution on a planet reaches the level of mental structures. The “discovery” (i.e. “detection”, i.e. “apo-kalypse”) of the laws of nature will start technological progress because this provides more power. Of course, like in our own history, many individual minds will understand the “devil-theorem” quite early, since the laws of logic are more fundamental than the laws of nature. But in the fight between “God and Devil”, dia-bolos (i.e. “he who throws things into disorder”) will prevail because he is always quicker than the creator of true complexity.

Thus, any planet with intelligence is likely to run into our kind of technological crisis and to approach global ecological or social disaster. Still, I call it a crisis, and not the end. When deadly consequences of this “progress” are felt on the critical time-scale (the own life-time) by a majority, insight into the logical pre-conditions of creation may become dominant in the global society of minds. It may then still be possible to self-organize the restriction of power and of the speed of innovation, and to shift the front of evolution to the mind – where creation of new complexity is possible without the destruction of its whole basis.

Conclusions concerning SETI are obvious. If there are others in our universe, they will not be interested in simple material structures, except during a few generations before that crisis. Mind will recognize itself as infinitely more complex, i.e. valuable. Topics like astronomy would play a negligible role in an “Encyclopedia Galactica”. If civilizations transmit signals, they will probably not use “variations of something expected”, as William Calvin proposed here “because radio-astronomers are interested in pulsars” [4]. For mind the only interesting thing in the universe will be other mind. Even the “acquisition signals” (though probably on “magic frequencies” – e.g. as favoured by David Blair [7] might not be perceptible on the human timescale – another relevant remark by Jill Tarter [4].

Civilizations beyond the acceleration-crisis would not try and help others to overcome it, too. Not because they are selfish, but because such help is obviously impossible. They must know that many of us have understood the origin of the crisis, but that we can stop only (if at all) at the very edge of the abyss. The time-scale of interstellar communication is longer than that of our instability. After the development of radio-technology there is no time left for help. Earlier interference, however, before the onset of the instability, would not mean help but colonization – which is probably excluded by further mental evolution (or even by a fundamental incompatibility between long-distance space travel and a “mastering of the Devil”). Hence, there is nothing important which we could learn from aliens on the time-scale of the crisis, i.e. on the human time-scale. It’s all in our minds! Still, the discussion about whether we should listen or not, and why we don’t hear anything, may contribute a little to the understanding of the devil-theorem …


References
[1] Brandon Carter, “The anthropic principle and its implications for biological evolution”, Phil. Trans. R. Soc. Lond. A310, 347-363 (1983).
[2] John D. Barrow and Frank J. Tipler, The Anthropic Cosmological Principle, Oxford University Press, New York 1986.
[3] Frank J. Tipler, Letter to Physics Today, Sept. 1988, pp. 88 and 146.
[4] Panel discussion, 3rd Intern. Symp. on Bioastronomy, Val Cenis 1990, Bioastronomy (J. Heidmann, M. J. Klein Eds.), Springer, Berlin 1991.
[5] First in “On the World’s Ends”, preprint 1976 (publ. in Munich Social Science Review 1978/2, 91-99), last in Das Grundgesetz vom Aufstieg, Carl-Hanser-Verlag, München 1989.
[6] “Time and Complexity” in Proceedings of the Workshop on Gravitation, Magneto-Convection and Accretion at the Ringberg Castle, Tegernsee, May 28-31, 1989 (B. Schmidt, H.-U. Schmidt, H.-C. Thomas Eds.), Max-Planck-Inst. Proc. MPA/P2, Sept 1989. (Included as No. 2 in this collection of essays.)
[7] David Blair, in Bioastronomy, see [4].