Evolutionary Chance Mutation: A Defense of the Modern Synthesis' Consensus View

Abstract

[Disponible en ligne : http://hdl.handle.net/2027/spo.6959004.0002.003]International audienceOne central tenet of the Modern Evolutionary Synthesis (1930s-1950s), and the consensus view among biologists until now, is that all genetic mutations occur by "chance" or at "random" with respect to adaptation. However, the discovery of some molecular mechanisms enhancing mutation rate in response to environmental conditions has given rise to discussions among biologists, historians and philosophers of biology about the "chance" vs "directed" character of mutations (1980s-2000s). In fact, some argue that mutations due to a particular kind of mutator mechanisms challenge the Modern Synthesis because they are produced when and where needed by the organisms concerned. This paper provides a defense of the Modern Synthesis' consensus view about the chance nature of all genetic mutations by reacting to Jablonka and Lamb's analysis of genetic mutations (2005) and the explicit Lamarckian flavor of their arguments. I argue that biologists can continue to talk about chance mutations according to what I call and define as the notion of "evolutionary chance," which I claim is the Modern Synthesis' consensus view and a reformulation of Darwin's most influential idea of "chance" variation. Advances in molecular genetics are therefore significant but not revolutionary with respect to the Modern Synthesis' paradigm

Epigenetically facilitated mutational assimilation: epigenetics as a hub within the inclusive evolutionary synthesis

“…Which specific mutations occur is not determined by the environment itself, but the functional portions of the DNA molecule where the mutation rate changes have the potential to be guided by the environment via epigenetic marks, promoting genetic variation in these loci upon which selection can act, thus leading to epigenetically facilitated mutational assimilation. Thus, the evolutionary outcome is similar to that of directed mutations, although each mutation is still non-directed [for a more complete discussion of this topic, see Pocheville & Danchin, 2017; for a discussion about randomness in biology see Merlin, 2010 andRazeto-Barry &Vecchi, 2017]. Nonetheless, there are important differences.…”

Monod's conception of chance: Its diversity and relevance today

“…Thus, it should be defined more precisely in order to deal with attacks against its current validity. But this is the topic of another paper [8]. The important point to stress here is the univocal character of such usual answer about Monod's conception of chance: it is limited to one specific concept of chance and does not exhaust the several meanings Monod attributes to it, which is particularly apparent in Le hasard et la ne´cessite´.…”

Explanation in Biology

“…Actually, the history of chance reveals that this idea is just one way to conceive it. Let us take as an example the specific (biological) notion of "evolutionary chance", which is at the core evolutionary theory since Darwin (Merlin 2010), in order to understand Millstein's thesis. Amongst others, Millstein (2011) makes this point by using the example of radioactive decay, which is usually considered a fundamentally indeterministic phenomenon of the quantum level (in other terms, an event without any cause at its origin).…”