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The Clay Life Hypothesis
| Article
# : |
12126 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
12 / 1987 |
3,024 Words |
| Author
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Graham Cairns-Smith
Graham Cairns-Smith is a reader in the Chemistry Department at
Glasgow University and author of Seven Clues to the Origin of
Life (London and New York: Cambridge University Press, 1985). |
…there should be no combination of events for which the wit of man cannot conceive an explanation. Simply as a mental exercise, without any assertion that it is true, let me indicate a possible line of thought. It is, I admit, mere imagination; but how often is imagination the mother of truth?
--Advice of Sherlock Holmes, from The Valley of Fear
The Oxford English Dictionary gives one of the meanings of clay as "the earthly or material part of man." This reflects an ancient myth, appearing in many cultures, that man was formed originally from clay. One can perhaps understand the line of thought. Clay is a commonly available material and, although formless itself, can readily have form imposed on it. A fine piece of sculpture even seems to have a kind of life in it. So perhaps the Great Sculptor first made man and other living things from clay. It is a vivid poetic image, but might there just be a grain of literal truth in it?
Many scientists say that indeed clay minerals are likely to have been involved in the origin of life. This is not to say that any organisms of the sort we know today were ever made out of clay, as in the Creator-Sculptor myth, but that clay minerals may have helped to initiate an evolutionary process that would head eventually to all the forms of life now on the earth.
According to the conventional view of how life started on the earth, the first proto-organisms--the first things able to evolve by Darwin's mechanism of natural selection--were made of much the same materials as organisms now; thus they must have arisen from some kind of stockpile of the required molecular components--some kind of "primordial soup." In that case, Darwinian evolution proper must have been preceded by a "chemical evolution" to bridge the gap between very simple molecules such as methane, supposed to have been present in the early atmosphere, and the more complex "molecules of life."
Stanley Miller's famous experiment of 1953 was an encouraging beginning. Miller simulated a primordial thunderstorm in the laboratory by passing sparks through a mixture of gases. This mixture included methane, then thought to have been a major constituent of the early atmosphere on the earth. Organic molecules were indeed produced, including some of the amino acids out of which proteins are made. It looked as if the gap between non-life and life might be
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