Big bang in Antarctica - killer crater found under ice, EurekAlert!, 1-Jun-2006, Pam Frost Gorder, Ohio State University ...
Whatever caused the Permian extinction - not to mention the other four of the `Big Five' mass extinctions - the bottom line is that without it (and indeed all of them) we would not be here! ... Continued from part #1
I was reading a 1982 essay by the late Ernst Mayr on the unlikelihood that there is extraterrestrial intelligent life and therefore that SETI was a waste of time. I knew that Mayr had in 1988 pointed out that because "each step leading to the evolution of intelligent life on earth was highly improbable and that the evolution of the human species was the result of a sequence of thousands of these highly improbable steps", therefore "It is a miracle that man ever happened, and it would be an even greater miracle if such a sequence of improbabilities had been repeated anywhere else" (my emphasis):
"Looking at the SETI project from a biologist's point of view ... I demonstrate that each step leading to the evolution of intelligent life on earth was highly improbable and that the evolution of the human species was the result of a sequence of thousands of these highly improbable steps. It is a miracle that man ever happened, and it would be an even greater miracle if such a sequence of improbabilities had been repeated anywhere else." (Mayr, E.W., "Toward a New Philosophy of Biology: Observations of an Evolutionist," Harvard University Press: Cambridge MA, 1988, p.5)
Here are just three in that "sequence of thousands of highly improbable steps," which if they had not happened, we would not be here:
1) "an astonishing, unique event 1800 million years ago the first eukaryote originated, a creature with a well-organized nucleus and the other characteristics of `higher' organisms":
"After the origin of life, i.e. 3.8 billion years ago, life on Earth consisted for 2 billion years only of simple prokaryotes, cells without an organized nucleus. These bacteria and their relatives developed surely 50-100 different (some perhaps very different) lineages, but none of them led to intelligence in this enormously long time. Owing to an astonishing, unique event that is even today only partially explained, 1800 million years ago the first eukaryote originated, a creature with a well-organized nucleus and the other characteristics of `higher' organisms. From the rich world of the protists (consisting of only a single cell) there eventually originated three groups of multicellular organisms: the fungi, the plants and the animals. But none of the millions of species of fungi and plants was able to produce intelligence." (Mayr, E.W., "The Search for Extraterrestrial Intelligence," in Zuckerman, B. & Hart, M.H., "Extraterrestrials: Where Are They?," , Cambridge University Press: New York, Second edition, 1995, pp.153-154)
2) the origin of higher intelligence in only one phylum "the chordates," in only one lineage of chordates' "the vertebrates," in only one lineage of vertebrates, "the mammals," in only one order of mammals, the primates (not mentioned by Mayr):
"The animals (Metazoa) branched out in the Precambrian and Cambrian to about 60-80 lineages (phyla). Only a single one of them, that of the chordates, led eventually to genuine intelligence. The chordates are an old and well-diversified group, but only one of its numerous lineages, that of the vertebrates, eventually produced intelligence. Among the vertebrates a whole series of groups evolved, types of fishes, amphibians, reptiles, birds, and mammals. Again it was only a single lineage, that of the mammals, that led to high intelligence. The mammals had a long evolutionary history which began in the Triassic, more than 200 million years ago, but only in the latter part of the Tertiary, i.e. some 15-20 million years ago, did higher intelligence originate in one of the c. 24 orders of mammals." (Mayr, 1995, p.154)
and 3) from that one order of primates, only one species, "Homo sapiens " out of a total of "perhaps as many as 50 billion species, since the origin of life," "achieved the kind of intelligence needed for the establishment of a civilization":
"The elaboration of the brain of the hominids began only about 3 million years ago, and that of the cortex of Homo sapiens only about 300 000 years ago. Nothing demonstrates the improbability of the origin of high intelligence better than the millions of phyletic lineages that failed to achieve it. How many species have existed since the origin of life? This figure is as much a matter of speculation as the number of planets in our Galaxy. But if there are 30 million living species, and if the life expectancy of a species is about 100 000 years, then one can postulate that there have been billions, perhaps as many as 50 billion species, since the origin of life. Only one of these achieved the kind of intelligence needed for the establishment of a civilization." (Mayr, 1995, p.154)
Which reminds me, that Julian Huxley, co-founder of the Neo-Darwinian Modern Synthesis, also pointed out in 1941 that "not merely has conceptual thought been evolved only in man: it could not have been evolved except in man," there being "but one path of unlimited progress through the evolutionary maze" and so "The course of human evolution is as unique in the profounder sense of being the only path that could have achieved the essential characters of man":
"We are now in a position to define the uniqueness of human evolution. The essential character of man as a dominant organism is conceptual thought. And conceptual thought could have arisen only in a multicellular animal, an animal with bilateral symmetry, head and blood system, a vertebrate as against a mollusc or an arthropod, land vertebrate among vertebrates, a mammal among land vertebrates. Finally, it could have arisen only in a mammalian line which was gregarious, which produced one young at a birth instead of several, and which had recently, become terrestrial after a long period of arboreal life. There is only one group of animals which fulfils these conditions-a terrestrial offshoot of the higher Primates. Thus not merely has conceptual thought been evolved only in man: it could not have been evolved except in man. There is but one path of unlimited progress through the evolutionary maze. The course of human evolution is as unique as its result. It is unique not in the trivial sense of being a different course from that of any other organism, but in the profounder sense of being the only path that could have achieved the essential characters of man." (Huxley, J.S., "The Uniqueness of Man," in "The Uniqueness of Man," Chatto & Windus: London, 1941, Third impression, pp.15-16)][Concluded in part #3]
Stephen E. Jones, BSc (Biol).
`Evolution Quotes Book'
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