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p.1161 despite their differences, whether mythic, magic, or scientific, all explanatory systems operate on a common principle. In the words of the physicist Jean Perrin, the heart of the problem is always "to explain the complicated visible by some simple invisible"... Whether mythic or scientific, the view of the world that man constructs is always largely a product of imagination.
p.1161 To produce a valuable observation, one has first to have an idea of what to observe, a preconception of what is possible. Scientific advances often come from uncovering a hitherto unseen aspect of things as a result... of looking at objects from a different angle.
p.1162 Nature functions by integration. Whatever the level, the objects analyzed by natural sciences are always organizations, or systems.
p.1162 At each level, new properties may appear which impose new constraints on the system... But as a general rule, the statements of greatest importance at one level are of no interest at the more complex ones.
p.1163 Complex objects are produced by evolutionary processes in which two factors are paramount: the constraints that at every level control the systems involved, and the historical circumstances that control the actual interactions between the systems. The combination of constraints and history exists at every level, although in different proportions.
p.1163 Natural selection is the result of two constraints imposed on every living organism: (i) the requirement for reproduction, which is fulfilled through genetic mechanisms carefully adjusted by special devices such as mutation, recombination, and sex to produce organisms similar, but not identical, to their parents, and (ii) the requirement for a permanent interaction with the environment because living beings are what thermodynamicists call open systems and persist only by a constant flux of matter, energy, and information.
p.1163 Natural selection has no analogy with any aspect of human behavior. However, if one wanted to play with a comparison, one would have to say that natural selection does not work as an engineer works. It works like a tinkerer - a tinkerer who does not know exactly what he is going to produce but uses whatever he finds around him... in short he works like a tinkerer who uses everything at his disposal to produce some kind of workable object.
p.1164 The tinkerer... always manages with odds and ends. What he ultimately produces is generally related to no special project, and it results from a series of contingent events, of all the opportunities he had to enrich his stock with leftovers. As was discussed by Levi-Strauss (5), none of the materials at the tinkerer's disposal has a precise and definite function. Each can be used in a number of different ways. In contrast with the Engineer's tools, those of the tinkerer cannot be defined by a project.
p.1164 Often, without any well-defined long-term project, the tinkerer gives his materials unexpected functions to produce a new object... Evolution behaves like a tinkerer who, during eons upon eons, would slowly modify his work, unceasingly retouching it, cutting here, lengthening there, seizing the opportunities to adapt it progressively to its new use.
p.1164 Evolution does not produce novelties from scratch. It works on what already exists, either transforming a system to give it new functions or combining several systems to produce a more elaborate one.
p.1165 Small changes modifying the distribution in time and space of the same structures are sufficient to affect deeply the form, the functioning, and the behavior of the final product - the adult animal. It is always a matter of using the same elements, of adjusting them, of altering here or there, of arranging various combinations to produce new objects of increasing complexity. It is always a matter of tinkering.
p.1165 Sex is one of the most efficient inventions of evolution.
p.1166 As Simpson (4) pointed out, the interplay of local opportunities - physical, ecological, and constitutional - produces a net historical opportunity which in turn determines how generic opportunities will be exploited. It is this net historical opportunity that mainly controls the direction and pace of adaptive evolution.
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