Endurance of life : the implications of genetics for human life / Macfarlane Burnet.

  • Burnet, F. M. (Frank Macfarlane), Sir, 1899-1985.
Date:
1978
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Endurance of life : the implications of genetics for human life / Macfarlane Burnet. Source: Wellcome Collection.

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    6 Endurance oí Life early in this century. It is clear enough that Ufe must have evolved in hquid water and the process could not have begun until the first seas were well established on the cooling earth. The situation then must have been such that an almost infinite variety of relatively small organic molecules could form at random in the warm, primitive seas. Between that stage and the appearance of self-reproducing micro¬ organisms equivalent to primitive bacteria there is an enormous conceptual gap. But the time gap is also large, possibly as much as 1000 million years. If that primitive organism was created by an accumulation of random events—awJ there is no other conceivable process within the universe known to science—iht chance of its occurring must have been almost infinitely small. But it did occur, and all that can be said is that, if the circumstances are right—the numbers of organic molecules in the upper layers of all the water on earth, the infinite variety of accidental occurrences, and the almost infinite lapse of time represented by 1000 million years—anything that can happen will happen. Somehow the micro-organisms that have been found in South African rocks 3000 million years old came into being. They must have had a chemical structure based on DNA and protein and a turnover of protein and energy handled by enzymes. Once the organismal pattern had been laid down, there is no special intellec¬ tual difficulty in accepting that an evolutionary process could deve¬ lop the general sequence of organisms that we can follow through the geological record. Most of the really difficult and interesting things must have taken place in that first 1000 million years. Without making any attempt to speculate about the chemistry of what took place, one can consider some phases that could be relevant to the understanding of death. The primitive meaning of death Death is clearly impossible until we have some entity that corre¬ sponds to our definition of Ufe or living matter. Probably the most basic definition is that Ufe is the capacity to reconstruct a repUca of a complex pattern of organic molecules. This would include some laboratory artifacts, but that does not disquaUfy it. As soon as large molecules could build up larger complexes by bringing in smaller molecules, and these complexes break up into two or some other smaU number of units with similar capacity, a process toward life was under way. That process would at first be fragile in the extreme. An abrupt rise in temperature or a switch of the water to a more acid or a more alkaUne reaction would probably destroy the system and in a sense kill the tentative approach to Ufe. True death could hardly be