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Chapitre D'ouvrage Année : 2010

Complex causality as the root of the structure/function relation problem: 1/ general considerations; 2/ the example of the bone tissue

Résumé

Biological functions, at all integrative levels of biology, are readily understood as the justification (or explanation) of the actual occurrence of the structures involved into their execution. This brings back directly to Aristotelian " final causes " and it is why modern epistemologists have struggled to offer concepts of function rid of any finalism. The two current answers, known as the etiological and systemic concepts of function respectively echo Mayr's distinction between historical and functional biology (1961). Those two aspects of biology convey either the historical (phylogenetic) or functional (mechanistic) modes of explanations for every actual structuro-functional occurrences. Each aspect is set within distinct epistemological (experimental/nomological vs. comparative/historical) frameworks, dealing with the analysis of proximate and ultimate causes, respectively . A third point of view on causal explanation of form/function relationships was reintroduced in modern science by Seilacher (1970) and Gould, (2002) namely a structuralist (or constructional) input which mainly deals with the constraints (eg. topological) imposed by the materials organisms are built from. Accordingly, three general aspects of causation, historical, functional and structural, may be involved together in the origin of any form/function relationship in biology. Integrating them should bring satisfactory causal explanations of empirical data. However, little progress has been accomplished in practice towards this goal, because a methodologically efficient tool was lacking. We have applied a new statistical method which allows partitioning the variation of a given biological trait among the three causal factors evoked above to analyze growth function in bone. 1/ Historical component. The variation of bone growth rates contains a significant phylogenetic signal, suggesting that the observed patterns are partly the outcome of shared ancestry. 2/ Functional causation. Resting metabolic rate may determine the maximum possible bone growth rate. 3/ Structural constraint. While soft tissues grow through a multiplicative process, growth of mineralised tissues is accretionary (additive, i.e. it occurs only at free surfaces). Bone growth of many amniotes partially circumvents this topological constraint by new bone being laid down not only at the external surface of the bone shaft, but also within cavities included in the bone cortex as it grows centrifugally. The three causal components interfere a great deal: i.e. the functional causation is in part phylogenetically structured. Accordingly, it becomes possible now to decipher quantitatively the complex causality of the structure/function conundrum.
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hal-00596867 , version 1 (30-05-2011)

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  • HAL Id : hal-00596867 , version 1

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Armand de Ricqlès, Jorge Cubo. Complex causality as the root of the structure/function relation problem: 1/ general considerations; 2/ the example of the bone tissue. Gayon J., de Riclès A. Les fonctions : des organismes aux artefacts, Presses Universitaires de France, pp.179-188, 2010. ⟨hal-00596867⟩
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