48 Life: Its Nature and Origin 



of primeval life. Because organisms almost certainly originated in 

 water, it is significant that Fox's proteinoids form cell-like spherules 

 that persist over a moderate temperature range and have an outer 

 membrane through which water is lost or absorbed with changes 

 in salt concentrations in the environment. 



Because proteins normally have a fairly short life in water, the 

 persistence of these proteinoid spherules for several weeks may be 

 all that could be expected of such a structure composed of protein 

 alone. Among the most effective substances which protect proteins 

 from decomposition are the nucleic acids. Perhaps some nucleic 

 acid precursors such as ureidosuccinic acid, which was formed in 

 the thermal experiments, would be effective protectors likewise. 

 Living cell membranes are thought to be composed of oriented 

 lipoproteins (Upjohn, 1958), in which the protein fraction is pre- 

 sumably protected by fat molecules (lipid); whether such protec- 

 tion was available and involved when life first started is not known. 



Fox (1957, 1959) has proposed an interesting hypothesis from 

 the results of his thermal experiments. He suggests that in pockets 

 of hot, compressed gas rising through fissures in the crust of the 

 earth, simple compounds recombined to form biological staples, 

 and these staples likewise recombined to form macromolecules. 

 Furthermore, if the gas escaped through a CRistal fissure into a 

 warm or hot ocean, the proteinoids would form "cells" containing 

 proteins and nucleic acid precursors. Thus a primeval protein- 

 nucleic acid system embodied within the confines of a membranous 

 "cell" wall would be formed automatically and rapidly from gases 

 arising from within the earth. 



A description of idealized cells must stress the orientation as well 

 as the chemistry of molecules. Hence, the physical as well as the 

 chemical properties of macromolecules such as proteins must be 

 fitted into any explanation of the origin of life. Some proteins ap- 

 proximate a crystalline organization under certain conditions. Thus 

 fibrils of collagen, from cartilage or muscle (Fig. 21a), may be 

 dispersed in weak acetic acid in such a manner that the molecules 

 of collagen are completely randomized (Fig. 21/;). When the 

 proper amount of sodium chloride is added to this mixture, the 

 collagen molecules spontaneously reassemble into long fibrils in 

 which the molecules are arranged in a crystalline type of organiza- 

 tion (Fig. 21c), Thus, under certain conditions of the environment, 

 a great deal of order is inherent in the physical nature of some 

 organic molecules, an order resembling that found in living or- 

 ganisms (Fig. 21c/). 



