Christian Défarge

Experimental Silicification of Thermophilic Microorganisms. Relevance for Early Life on Earth and Mars

This issue of Origins of Life and Evolution of Biospheres contains the abstracts of the scientific contributions presented at the 2008 ISSOL Meeting, which was held in Florence (Italy) on 24–29 August, 2008. The Symposium’s main objectives were to bring together scientists working in different areas of the study of the origin and early evolution of life, to stimulate discussion on this fundamental process and to have an appraisal of the most recent advances in this multidisciplinary field that combines research from space sciences and astrophysics, to chemistry, geology, paleontology, genomics, molecular biology, history and philosophy of science, among others. The meeting was attended by about 350 scientists from all over the world, and more than 310 presentations were given, including 260 posters. This volume collects almost all the contributions, which are an up-to-date account of the state of the knowledge on this exciting area of scientific and educational pursuits. It is with great pleasure that I acknowledge the contributions of different authors in assuring the prompt publication of the OLEB Special Issue. I would also like to express my thanks to the Editor of OLEB, Alan W. Schwartz, and Springer for the publication of the Proceedings.Darwin fully acknowledged the difficulties in seeing how such a thing as an eye might have nevolved through natural selection (Darwin 1859, Chapter 6), but he knew of many lesser nexamples that could clearly have arisen that way. If the detailed, well adapted, shape of a nbird’s beak could have arisen through natural selection without the need for a prior creator, nthen Nature can indeed act as if it were an engineer, producing what seem to be purposebuilt nstructures, and giving an impression of foresight. But, really, no mysterious view of nthe future is required. What is absolutely required for nature’s engineer to get to work is nremarkable all the same: it is a kind of memory of what succeeded in the past. So this is the nquestion that should be the first focus of our attention: What are the simplest genetic nmemories that we can imagine working in a primitive geochemical milieu? The RNA world nidea has been a great inspiration, but this system is already too sophisticated and too far nfrom ordinary geochemistry to be a likely beginner in the evolution game. I have suggested nthat the mineral world provides us with several candidates for more primitive genetic nmaterials (Cairns-Smith 2005, 2008 and references therein). I will argue against the usual napproach to the puzzle of the origin of life, which looks for ways in which the present nmolecules of life might have arisen as a prelude to a Darwinian evolution. I think that this nputs the cart before the horse. I will suggest rather that natural selection came first, based on ninorganic materials, and that “the molecules of life” were a crucial but later part of the story