Seminar #63: On the origins of genetic systems
This week we will have another special Life and Mind seminar that connects nicely with many of the recent discussions on the essential organization of the living and evolution:
On the origins of genetic systems
University of Compiègne, France
Date: Wed., March 24, 2010
Time: 11:00-12:30 (NOTE UNUSUAL TIME)
Room: ARUN 401 (The usual Alergic Room)
Pasteur showed that contemporary organisms always derive from other already existing organisms. Nowadays, there is no spontaneous generation, not even for the simplest extant organisms such as bacteria. However, if life does always come from life, and if we go back step by step in time, there is a logically inescapable conclusion: we must arrive in the end at the very first organisms of all, and these by definition must have arisen by spontaneous generation. So, how is this possible?
All living organisms, past and present, are dissipative structures; they are not “things”, but processes whose dynamic existence depends on their being linked to a flow of energy and matter. Now simple dissipative structures can and do arise by spontaneous generation; examples are Bénard cells in the laboratory, and in natural settings whirlpools and cyclones. However, such structures are intrinsically ephemeral; they disappear as soon as external conditions over which they have no control are no longer sufficient for their maintenance. We may consider that “biological” individuation comes about when the functioning of a primitive dissipative structure does manage to exert some control over its conditions of existence; plausibly, when a metabolic process (a sort of “chemical whirlpool”) produces a membrane within which it can be stabilized. A model of this is the tesselation automaton of autopoïesis.
The next point, however, is that a minimal model of autopoïesis of this sort would not seem to have the capacity to evolve, to complexify through phylogenesis. My working hypothesis is that for this to occur, some sort of “genetic system” is necessary; not just a system of traces produced by the metabolic processes and which in return reinforce those processes, but a differential system where differenttraces are associated with different processes. This could set up the Darwinian process of variation and selection, so that evolution could “go somewhere”.
Where might such a primordial genetic system have come from, and what might it have been like? In all contemporary organisms, there is an ubiquitous genetic system composed of DNA and proteins. However, genetic engineering has shown that if we try to simplify this system, attempting to go back in evolution to its origin, we cannot go very far; the “minimal genome” for functional viability and self-reproduction has to retain about 50% of the genes of the simplest extant organisms; and even more important, it is still a DNA-protein system. The problem is that this system is far too complicated to have arisen by “spontaneous generation”, even in the context of minimal autopoïetic organisms.
In this talk, my focus will be to address this question of the “missing link”. A key point will be to clarify the exact role and nature of “genes”, in an abstract sense. In spite of a lot of gene-centred hype, genes are not the “architects” of living cells, and even less are they the masons who actually build the organisms. By cutting genes down to size, it becomes possible to understand how they might have arisen. And even “cut down to size”, I will argue that they have played a decisive role in making it possible for living organisms to complexify in the course of phylogenesis.