Soups & SELEX for the origin of life.

Abstract

The theory of evolution quickly brought up the most fascinating question in biology: the origin of life. How did life emerge? The biggest challenge in this endeavor to understand how life could have emerged without a controller is to unravel the chemical processes that made the synthesis of complex molecules containing information possible. Already at high school I was totally caught by Oparin's hypothesis that simple unicellular organisms evolved from simple organic molecules, which in turn originated from simple inorganic molecules present in the early atmosphere of our planet. Oparin and Haldane coined the idea of “primordial soup” experiments. For my “Matura” (that is the name of the exam you do in Austria, when you finally leave high school) I got Stanley Miller's famous primordial soup experiments as question. I just now realize that ever since SOUP & SELEX experiments are the ones I find most seminal for shaping our view of the world. I still consider these experiments as the breakthrough in biology of the 20th century because it opened up a whole new field clearly suggesting that one day it might be possible to understand how life emerged. Until the discovery of microorganisms by Louis Pasteur, fermentation by microorganisms was thought to be the product of spontaneous generation. Until Eduard Buchner demonstrated that fermentation could occur outside a living organism, in a test tube, it was the belief that only living cells were able to catalyze biochemical reactions. When in 1897 Bucher reported that a cell-free extract from yeast was able to ferment sugar, the field of biochemistry was invented and the analysis of chemical reactions taking place in living cells became accessible. There have been several theoretical approaches to the emergence of life as a self-replicating system, whereby the most essential part of all these concepts is the idea that complex systems can evolve from simple compounds without an external controller. This was indeed a revolutionary thought! As Erwin Schrodinger pointed out in 1944, it looks like living organisms bypass the second law of thermodynamics because they are able to evolve to complex systems out of disordered compounds ignoring Maxwell's Demon. Manfred Eigen, Leslie Orel and Stuart Kauffmann coined theoretical backgrounds on which chemists could develop experimental set ups. Combinatorial events of simple chemical reactions could lead to stably replicating populations of increasing complexity.