This adaptation led ultimately to the evolution of protein synthesis and the genetic code. The evolution of protein synthesis is not understood in detail. One of the great challenges of the problem of the origins of life is to demonstrate in the laboratory how polynucleotides, without the help of preformed enzymes, could have replicated and begun to control the synthesis of peptides with determined sequences. Once this has been done we shall be well on our way to understanding the origins of the first living cells. The Composition of the Primitive Atmosphere Geological and geophysical evidence is insufficient to allow us to state with any precision what conditions were like on the surface of the primitive earth.
Arguments concerning the composition of the primitive atmosphere are particularly controversial.
It is important, therefore, to state our own prejudice clearly. We believe that there must have been a period when the earth's atmosphere was reducing, because the synthesis of compounds of biological interest takes place only under reducing conditions. We are not certain that either assumption is correct for the primitive earth. On the other hand, it may not. There is clearly a wide range of choices of intermediate models.