It has been argued that the limited set of proteins used by life as we know
it could not have arisen by the process of Darwinian selection from all
possible proteins. This probabilistic argument has a number of implicit
assumptions that may not be warranted. A variety of considerations are
presented to show that the number of amino-acid sequences that need have been
sampled during the evolution of proteins is far smaller than assumed by the
argument.Comment: 14 Pages; International Journal of Astrobiology / FirstView Article /
October 2012, pp 1