Primordial Soup Evolution

Molecular Knowledge in The Primordial Soup

Table 5.3 calculates the knowledge in the B chain of insulin assuming that the protein evolved in the primordial soup.

Table 5.3: Molecular Knowledge in Insulin B Chain

Total = 211 bits.

* Any position with a gap does not need an amino acid and therefore the knowledge is set to 0 bits.

  

Example calculation: At position 7, only leucine is found in the alignment. Nevertheless, the technique to calculate knowledge assumes that the other amino acids in this group are allowed. The number of blocks labeled with the 5 amino acids belonging to group 1 in the truck (figure 5.1) is 413,200. There are 3,520,880 total blocks. So the knowledge is 3.32 x log [3,520,880/413,200] = 3.1 bits.

   Notice that no position can ever contribute less than 2 bits. If all 20 amino acids are found at a particular position, the position still contributes 2 bits. This accounts for the amino acids not used by life found in the soup.

   The average knowledge per amino acid is calculated as follows: molecular knowledge per amino acid = 211 bits/30 amino acids or 7 bits per amino acid.

   Notice that the molecular knowledge in the B chain increased from 76 bits with the genetic code to 211 bits with the primordial soup. The average knowledge per amino acid with the genetic code is only 76/30 or 2.5 bits per amino acid.

   Because of the nature of logarithms, the implications are dramatic. Suppose that one of the first proteins to evolve contains 100 amino acids, and that 30% of this protein shows a conservation pattern similar to insulin.

Knowledge today = 100 amino acid x 2.5 bits per amino acid x 30%
= 75 bits

Odds of evolving today are 1 time in 2⁷⁵ tries or 1 time in 4 x 10²² tries. This could happen with enough tries.

Knowledge in Primordial Soup = 100 x 7 bits per amino acid x30%

                + 100 x 2 bits per amino acid x 70%

                        350 bits

Odds of evolving in the primordial soup are 1 chance in 2³⁵⁰ or 1 time in 2.2 x 10¹⁰⁵ tries. This can never happen.

   Before life exists, chance will require an incredible number of tries to create knowledge, and the vastness of space, the number of atoms in the universe, and the incredible age of the universe do not make a dent in the problem. Nature simply cannot accumulate enough tries to overcome the poor odds.

   Finally, this chapter had to make quite a few assumptions. Some readers may be concerned about these assumptions, but realize that almost every assumption was for the benefit of protein evolution. For example, this chapter assumed that primordial soup did not contain aldehydes, carboxylic acids, and amines. This assumption is obviously false, but it greatly improves the chance for a protein evolving because it eliminates many side reactions. Also the amino acids not listed in Miller’s table (because they are not present in significant quantities), are assumed to be in the soup at a very generous level. Allowing every star in the universe to have an earthlike planet is certainly a generous assumption, but perhaps the most generous assumption is to allow every single one of these planets to be composed entirely of peptide chains each containing 150 amino acids. This assumption is only rivaled by the next one that allows these peptide chains to break down and reform every year, and even with all of these generous assumptions, the probabilities do not budge from zero.

   Scientists who believe that nature can create molecular knowledge before life rely on faith to justify their opinion, because the math tells a different story.

References:

1) Keefe and Szostak, “Functional Proteins from a Random Sequence Library,” Letters to Nature, 410: 715-718, 2000.
2) Miller, Which Organic Compounds Could have Occurred on the Prebiotic Earth?, Cold Spring Harbor Symposium of Quantitative Biology Volume L11, 17-25, 1987.
3) Miller, Orgel, The Origins of Life on Earth, Prentice Hall, 1974
4) Ehrenfreund, Glavin, Botta, Cooper, Bada, “Extraterrestrial amino acids in Orguil and Ivuna: Tracing the parent body of CI type carbonaceous chondrites,” PNAS, 98: 2138-2141, 2001.

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