known to be 5,750 million years, within about 200 million 

 years, from studies of radioactively formed isotopes in 

 meteorites. There has therefore been a period of about 

 5,000 million years on this planet — the Pre-Cambrian — 

 during which the complicated molecules of life were being 

 built up from simple ones. 



Modern chemical research has now shown that the 

 essential constituents of living matter, proteins, are com- 

 posed of enormous long spiral molecules which are assem- 

 bled from the much smaller amino acid molecules obtained 

 from the breakdown of other proteins in an animal's food. 

 The assembly process takes place within the body cells, 

 under the control of ribonucleic acid molecules sent out 

 from the cell nuclei, the latter molecules being made in 

 the nuclei according to information contained in the struc- 

 ture of the chromosomal genes, which carry most of the 

 hereditary specification of the animal species in terms of 

 their chemical structure (the remaining information being 

 contained in the cell wall according to the latest studies). 

 The question of how the genes of the earliest organisms 

 came into being is probably to be answered in terms of the 

 deposition of carbon-containing molecules upon a crystal 

 matrix of an inorganic mineral, the organic molecules then 

 uniting in their close proximity to give large molecules. 

 It must be remembered that the early genes would be far 

 smaller and simpler than those occurring in organisms 

 today, since long evolution has evidently led to many in- 

 creases in complexity of the genes. Actually, modern genes 

 appear, according to the most recent research, to have 

 considerable redundant portions in their lengths; that is, 

 the specification of the species-specific characteristics of 

 an organism appears to be repeated to an extent greater 

 than is really necessary — this leads to greater reliability 

 in copying of the genes however. 



55 



