Disentangling the causes of development

The idea that genes explain the development of an organism (Monod 1970; Jacob 1981; Rosenberg 1997) offered a simple view of the causality of development. Yet many biologists and philosophers (Griffiths and Gray 1994; Lewontin 2000; Oyama 2000; Gilbert 2002; Minelli 2003; Robert 2004) have suggested that this idea was inadequate, both because genes never exert a causal influence in isolation, and because many other factors causally impact development.

The fundamental epistemological question of how to explain the development of a new organismnow comes back as a common issue for biologists and philosophers of biology, with an enriched and increasingly complex background, in which many different developmental causes are recognized (including “environmental” factors such as temperature, luminosity but also symbiotic entities), and are in addition considered as “co-constructed”, in the sense that each causal factor influences the other (Lewontin 2000).

As an example, it has been demonstrated that gut bacteria can activate some genes in mammals (those genes would not be activated otherwise) and that, depending on the type of bacteria found in the gut, different phenotypes can be obtained (Hooper and Gordon 2001; Gilbert and Epel 2009); this example, and many others, show that genes should not be seen as a “separate” cause from the environment, and that different causal factors can interact in a complex, “intertwined” manner.

What is at stake here, nonetheless, is the possibility ofconductingprecise and well-focused scientific research: if developmental causes constantly interact in complex ways, how can biologists in the lab choose a specific question to be addressed, and how can they contribute to the advancement of our understanding of development? This problem has been discussed by leading figures in philosophy of biology, including Philip Kitcher (2001) and Marcel Weber (2005). An essential objective of IDEM is to address this worry about the possibility of articulating a sophisticated conception of developmental causality with the requirements of an effectivescientific research.

The case of symbiont-induced development will be examined as a major test case, as it seems both to illustrate the intertwinement of developmental causesand to have led in the last ten years to a very focused and highly successful research program, using the most cutting-edge tools and molecular techniques (McFall-Ngai et al. 2013). These reflections will be confronted to the very dynamic debate currently held in philosophy of science and metaphysics of science over different conceptions of causality –and especially over the interventionist framework renewed by Jim Woodward (see Woodward 2003 and, for a contrasting perspective, Mumford and Anjum 2011), a framework now extensively discussed in philosophy of biology (Woodward 2010).

Thus, this IDEM sub-project will address the following questions:

  • What is the causal role of genes and other factors in development, and how to make sense of the claim that developmental causes are intertwined, i.e., influence each other? Does such a conception hinder practical scientific research?
  • Among the different philosophical frameworks about causality currently under discussionin philosophy of science and metaphysicsof science, which one is the most adequate to account for biological causes, and especially the intertwined causes involved in the construction and maintenance of a biological individual?
  • Confrontation to a specific case: In development, how do symbionts interact with the host, and in particular with the hostgenome?
  • Does ecological developmental biology, and in particular the demonstration of the role of symbionts in development across phyla, offer a richer account of developmental causality? Does it answer the “practical challenge”, according to which it would be extremely difficult to do actual research if all developmental causes influenced each other?


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