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DOES IT PAY TO ACQUIRE HIGH INTELLIGENCE? ERNST MAYR* I was surprised by the correspondence I had with various physicists after the publication of my note questioning the feasibility of the Search for Extraterrestrial Intelligence (SETI) project [I]. To my amazement many of them took it for granted that intelligence was a necessary development as soon as life originated on some planet. In spite of all of the developments in modern physics, there is apparently still a strong deterministic tendency among physicists. By contrast, I showed that among the more than a billion species that have existed on earth since the beginning of life, only a single one, Homo sapiens, acquired high intelligence. To be sure, a lower level of intelligence was reached by a number of warm-blooded vertebrates: among mammals, particularly among primates, carnivores, and whales; as well as among birds, among parrots and ravens. However none of this is high intelligence, sufficient to establish civilizations and communicate electronically. Every property of any living organism has evolved with the assistance of natural selection. When there is a high premium on a property—such as, for example, vision—it will be acquired repeatedly. Eyes or welldeveloped photosensory organs originated at least forty times independently in organisms [2]. One of my correspondents, a biologist, suggested quite perceptively that the lack of the repeated acquisition of high intelligence among the hundreds of millions of evolutionary lineages possibly suggests that there is not as high a selective premium for such a property as we assume. This is a thought that we anthropocentric humans, so proud of our intelligence, find difficult to accept. It is true, however, that all the other millions of species on earth are getting along fine without that property. They have other adaptations to cope with any life-threatening encounters and have the necessary instincts to cope with normally occurring situations. Whatever deficiencies there might *The Agassiz Museum, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138.© 1994 by The University of Chicago. All rights reserved. 0031-5982/94/3703-0875$01.00 Perspectives in Biology and Medicine, 37, 3 ¦ Spring 1994 337 be in their survival capacities are being compensated by selection for reproductive success. The final outcome is that they survive and prosper without benefit of high intelligence. There is a second factor to consider. High intelligence such as that found in the human species is perhaps not easily acquired. It requires a long infancy during which information can be obtained and stored that is later helpful in processing signals from the environment that facilitate survival. Also, a large brain is metabolically very demanding, and it is obviously not merely a coincidence that all cases of real intelligence are limited to warm-blooded animals. It is important to remember that even though the hominid line branched away from the chimpanzee line about five million years ago, the large brain of Homo sapiens was acquired only about 300,00 years ago; that is, only in the last 6 percent of hominid existence. The development of a very large central nervous system that permits high intelligence apparently requires a high level of parental care. As was shown by Stanley [3], this was possible only after the descent of the bipedal Australopithecus from trees was completed, thus freeing the mothers' arms for carrying the large and very incompletely developed human baby. It thus appears that the development of high intelligence in humans was made possible by a rather improbable sequence of evolutionary developments. By no means do I want to suggest that exactly the same evolutionary sequence is necessary for the development of high intelligence on other planets with life. What I do want to emphasize, however, are two things. First, the development of high intelligence is not at all an inevitable consequence of the existence of life. Second, there are very many other mechanisms and devices than intelligence to cope with survival and successful reproduction, mechanisms that apparently can evolve far more easily than high intelligence. REFERENCES 1.Mayr, E. Search for intelligence. Science 259:1522-23, 1993. 2.Salvini-Plouen, L., and Mayr, E. On the evolution of photoreceptors and eyes. In Evolutionary Biology, edited...


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