The study of the origins of life is recognised as one of the major scientific challenges of the XXI century; it mobilizes several conceptual fields and combines numerous aspects of the scientific knowledge in a variety of areas. Since 2006 and within the frame of its prospective and program-oriented policy, CNRS has created the interdisciplinary research program “Origins of Planets and Life”.
In the context of this programme, key questions are investigated: how planetary systems form and evolve, including the solar system and extrasolar planets, the origin and evolution of the organic matter in the planetary systems (from the dust grains to the comets, asteroids, meteorites and planets), the origin and composition of the early planetary atmospheres, as well as the diversity of planetary systems, the physico-chemical characteristics of the extrasolar planets, and the existence of telluric exoplanets. The processes and conditions that prevailed at the origins of life on Earth are also under intensive investigations. What conditions prevailed in the primitive Earth? What transitions are known to have led from the inanimate to primitive life? How can we recognise the first traces of life on Earth, what chemical biomarkers can we use for searching for living organism (now and in the distant past)? How can we detect signs of extraterrestrial life? What forms of life? Can we extrapolate life on Earth to other systems (in the solar system or in extrasolar planets)? These questions demonstrate how important it is to understand the formation and evolution of planets and to characterize the various planetary systems. Finally, historically- epistemologically- and philosophically-oriented questions must be addressed to highlight and better establish the causal links that bind these themes to one another. The Workshop “Origins of Life: Self-Organization and/or Biological Evolution?”, held on Oct. 3rd 2008, was organised by the CNRS Interdisciplinary programme “Origins of Planets and Life” at École Normale Supérieure in Paris. Specialists in biology, physics, chemistry, mathematics, astrophysics, Earth sciences, philosophy… developed in their respective research areas, their views on the origins of life on Earth as well as how the concepts linked to self-organization and biological evolution can bring new ideas to understand the origins and development of life on Earth. The goal of the workshop was to delineate the importance of these concepts and to initiate discussions between specialists in order to progress towards true interdisciplinary research. In Nature, two types of spontaneous structures exist: structures at equilibrium such as crystals, and structures not at equilibrium that constantly dissipate energy such as whirlpools requiring the participation of energy flows coupled by non-linear processes.
In the particular case when the source of non-equilibrium is a chemical reaction, such dissipative structures are studied by certain investigators, as “simple” archetypes of the mechanisms and conditions for the functioning of biological systems. Moreover, structures of reaction-diffusion are involved in certain aspects of the morphogenesis of living beings. Numerous molecules self-organize themselves in living organisms: actin and tubulin into filaments, lipids and proteins into membranes. Filaments and membranes are organized in cells that themselves are self-organized in tissues then in organs, and finally form the entire organism. Assemblies of molecules are formed and destroyed by weak interaction with binding energies comparable to the thermal energy, rendering them very sensitive to the external conditions and easily adaptable to those conditions. Such self-organization patterns are not a feature of living systems solely; they occur in many physical and chemical systems composed for instance of molecules that are amphiphylic (both hydrophylic and hydrophobic), leading the way from simple material to the construction of biomimetic and microrobotic systems.
Moreover, the theory of morphogenesis attempts to explain the shapes and dynamics of growth of macroscopic objects starting from the relatively simple laws of physics. These laws are well understood at the microscopic level. New theoretical work have demonstrated the power of using physical laws, coupled to the biological information on the growth processes.
Finally, the origin of life was marked by the transition from chemical reactions to self-replicating molecular entities capable of evolving by natural selection. The structure and function of many biological molecules and supramolecular assemblies are today accessible in simulated “prebiotic’’ conditions; nevertheless we are still unable to establish a link between these structures and the complex metabolisms at work in living matter. There is no doubt that self-organization constitutes a key concept to understand collective phenomena, be it at the chemical, biological of behavioural level. It characterizes the processes during which spatial structures collectively emerge from a multitude of interactions that arise from purely local information. In this framework, there is no need for global information as the local interactions are sufficient to provoke the emergence of the collective structures. However, it is now becoming important to understand how the local interactions led to a new level of organisation, how this information was introduced into matter, amplified and then transmitted in an evolving process characteristic of life.
Maryvonne Gérin et Marie-Christine Maurel