The Chances of a Protein Forming

Allow the soup that nature disallows. Millions of amino acids in the soup, hundreds of different kinds, roughly half of them in a left-handed form and half right-handed. Would the amino acids now connect up in long chains to make proteins? Would only the 20 kinds needed be selected by chance out of the hundreds of kinds in the soup? And from these 20 kinds, would chance select only the left-handed forms found in living organisms? And then line them up in the right order for each distinctive protein and in the exact shape required for each one?⁠⁷ Only by a miracle.

A typical protein has about one hundred amino acids and contains many thousands of atoms. In its life processes a living cell uses some 200,000 proteins. Two thousand of them are enzymes, special proteins without which the cell cannot survive. What are the chances of these enzymes forming at random in the soup​—if you had the soup? One chance in 10^40,000. This is 1 followed by 40,000 zeros. Written out in full, it would fill 14 pages of this magazine. Or, stated differently, the chance is the same as rolling dice and getting 50,000 sixes in a row. And that is for only 2,000 of the 200,000 needed for a living cell.⁠⁸ So to get them all, roll 5,000,000 more sixes in a row!

By now I felt that I was beating a dead horse. But I continued. Assuming that the soup did give us proteins, what about nucleotides? Leslie Orgel of Salk Institute in California has indicated nucleotides to be “one of the major problems in prebiotic synthesis.”⁠⁹ They are needed to make the nucleic acids (DNA, RNA), also called an overwhelming difficulty. Incidentally, proteins cannot be assembled without the nucleic acids, nor can nucleic acids form without proteins.⁠¹⁰ It’s the old riddle in chemical garb: Which came first, the chicken or the egg?

The final step of the six listed at the outset: a membrane. Without it the cell could not exist. It must be protected from water, and it is the water-repellent fats of the membrane that do this.⁠¹² But to form the membrane a “protein synthetic apparatus” is needed, and this “protein synthetic apparatus” can function only if it is held together by a membrane.⁠¹³ That chicken-and-egg problem all over again!