being selected on other planets, it is sometimes argued, is minimal. Faculties comparable with human intelligence do not have to evolve.
George G. Simpson (1964a) has questioned the assumption that extraterrestrial life is likely to emerge along similar paths to that taken on Earth, and draws a contrast between the deterministic view of the bioastronomers and a more opportunist view. Evolution, he stresses, is not goal-directed, there has been a ‘continual and extremely intricate branching’ with Man as ‘the end of one ultimate twig. The housefly, the dog flea, the apple tree and millions of other kinds of organisms are similarly the ends of others’ (ibid.: 773). Evolution, he points out, produces numerous dead ends and extinctions without issue. If humans disappeared it is not inevitable that they would be replaced by another intelligent species. There is no reason, he argues, to assume a continuous development from primitive organisms to human intelligence. The turtle, which can be traced back some 200 million years into the Mesozoic era, reveals that life can get by without too much intelligence. In terms of Darwinian survival, the most successful species are rats and beetles. The development of our neuro-anatomy was not merely unpredictable, he says, it was ramshackle. Our brains were pieced together over millions of years. Against this it might be objected that the hardware is unimportant; that what matters is the software: our thoughts, consciousness and problem-solving abilities, which can operate with different kinds of hardware. But this argument, concludes Simpson, is unsatisfactory, as it presupposes a free-floating intelligence independent of our brains – not to mention our natural and social history. In fact, the only way that such an argument can be supported is by an appeal to some Divine programmer, a view which is not likely to find acceptance among SETI scientists, says Simpson.
When contemplating the likelihood of an extraterrestrial intelligence similar to ours the appeal to large numbers, the vastness of the universe, is of limited value. Given an almost infinite number of locations it might be suggested that somewhere an extraterrestrial intelligence has evolved with an English grammar and vocabulary. Maybe they have cockney accents as well. If they speak English, it is inevitable that they will speak it with an accent. But these possibilities are not merely rare, or of low probability; they are unlikely to the point of being downright impossible, as they would require an incredible duplication of countless events in human history, its wars and invasions, to emulate one of the languages spoken by humans. However, if they are in the habit of monitoring our radio transmissions, then they might easily acquire some of the peculiarities of a language like English.
If Simpson is correct in his assertion that extraterrestrial life is unlikely to develop along similar evolutionary lines to terrestrial life, then it would appear that if intelligence is widespread throughout the galaxy it is probably the result of diffusion. Opponents of Simpson and the neo-Darwinists might, however, respond by raising questions concerning the assumption that evolution is neither law-like, predictable nor progressive. For it could be maintained that progress is a feature of evolution, and that progress towards greater levels of complexity, which
includes the development of self-consciousness and intelligence, is a law-like feature of evolutionary development. Evolutionists who shun notions like progress as unscientific may simply be confusing progress with destiny. Rigidly drawn dichotomies between ‘chance’ and ‘necessity’ continue to mislead. Evolution is neither a product of blind chance nor absolute necessity; it is a matter of probability determined by physical possibility. Moreover, SETI scientists have responded to Simpson’s argument by pointing out that the emergence of a technological intelligence need not replicate all the sequences of mankind’s development; in nature there are many different means of arriving at a similar goal.
Nevertheless, appeals to progress and complexity in evolution frequently rest on a highly selective range of examples. As Stephen J. Gould points out:
When we consider that for each mode of life involving greater complexity, there probably exists an equally advantageous style based on greater simplicity of form (as often found in parasites, for example), then preferential evolution towards complexity seems unlikely a priori. Our impression that life evolves towards greater complexity is probably only a bias inspired by parochial focus on ourselves.
Gould strongly rejects the view that human intelligence is a result of some natural evolutionary process of complexification. Homo sapiens, he says, could very well be ‘a tiny, late-arising twig on life’s enormously arborescent bush – a small bit that would almost surely not appear a second time if we could replant the bush from seed and let it grow again’ (ibid.: 70).
What do we normally mean when we speak of ‘intelligence’? It is difficult to define, but it should include several of the following: faculties for reasoning, creativity, inventiveness, imagination, foresight, reflection, an aptitude for learning and problem-solving and some communicative abilities. These should be employed in a manner which indicates a degree of co-ordination. In this respect it is a mistake to start from a definition of intelligence; rather, it is best to indicate what it actually does, and what it actually requires in order to function. Intelligent communication, for example, requires similar sensory equipment among members of a communicating group. This, however, is not a necessary feature among beings who share an identical environment. A desert can provide a home for humans, dogs, insects and rattlesnakes, none of which can communicate with each other. Our expectation that similar sensory receptors will be found among living beings sharing a similar terrestrial niche is dashed when we learn that the dog’s sense of smell is 15 million times stronger than ours, and that, despite sharing a similar exposure to light, the rattlesnake relies on nearby wavelengths with its infrared receptors which enable it to sense its warm-blooded prey in the dark. This suggests that an environment so radically different from Earth would yield yet another range of diversity.
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