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forms of extraterrestrial intelligence

In speculating about the guises that intelligence may assume elsewhere, it is worth remembering the diversity of intelligence that exists even on Earth, both within and between species. This broad terrestrial spectrum strongly suggests that among organisms that have evolved on other worlds, and adapted to different environments and perhaps with a different biochemical basis, there may be an even richer variety of intelligent forms, just as extraterrestrial life in general is likely to prove surprising and novel to us (see extraterrestrial life, variety of). However, some aspects of intelligence may not be so different from one planet to another. All creatures are subject to the same physical rules and, as Carl Sagan points out in his Dragons of Eden:1
Natural selection has served as a kind of intellectual sieve, producing brains and intelligences increasingly competent to deal with the laws of nature... [T]he same evolutionary winnowing must have occurred on other worlds that have evolved intelligent beings... I think we will find that much of their biology, psychology, sociology and politics will seem to us stunningly exotic and deeply mysterious. But I suspect we will have little difficulty in understanding each other on the simpler aspects of astronomy, physics, chemistry and perhaps mathematics.
That a common appreciation of physical science and mathematics (see mathematics, as a universal language) will exist among intelligent races is a fundamental assumption of those engaged in SETI. Yet we already know of species that appear highly intelligent and have an intuitive understanding of complex physics (see dolphins, as a form of alien intelligence) but that are completely non-technological. Furthermore, it may well be the case that outside of a certain technological "window", intelligent species are incapable or not interested in establishing contact (see Drake equation and extraterrestrial intelligence, more advanced than us).

The biological evolution of intelligence is slow, although as in the 5-million-year development of modern humans from an ape ancestor, it can undergo comparatively rapid spurts. By contrast, it is likely that technology can dramatically enhance intelligence over almost insignificant timescales. The human race now appears to be on the brink of this development with the first practical applications of brain-computer links. Once such connections are perfected and become freely available, it is difficult to predict what levels of intelligence a man-machine symbiosis might achieve.

The idea that sentient machines might be the ultimate product of life's evolution has long existed in fiction. The Greek god Hephaistos is described in the Iliad as having artificial women of gold to help him around the house. A bronze giant, Talos, was supposed to guard the shores around Crete. And in his witty satire Erewhon (1872), Samuel Butler suggested that machines are evolving faster than people because people tend and develop them. More recently, following the dawn of electronic computers, writers such as Arthur C. Clarke and Isaac Asimov have explored futures in which machines, both benign and malignant, partly take over human affairs. In view of the rapid progress made in computer technology and robotics over the past couple of decades, it no longer seems far-fetched that artificial intelligence may one day far exceed that of humans. Developments such as the Internet and prototype brain-computer links suggest that some form of part-human part-machine life-form might emerge in the not-so-distant future. Fictional explorations of such possibilities are commonplace – for example, Mr. Data and the Borg in Star Trek. As time goes on, and we see the pace of our own technological development far outstripping that of biological evolution, the conclusion becomes compelling that if advanced extraterrestrial intelligence exists then some of it at least may be partly artificial.2


  1. Sagan, Carl. The Dragon's of Eden. New York: Random House (1977).
  2. Bradbury, R. J. "Dyson Shell Supercomputers as the Dominant 'Life Form' in Galaxies," paper presented at Bioastronomy 99: A New Era in Bioastronomy, Kohala Coast, Hawaii, August 2-6, 1999.

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