Quantifying the Left-Handed
Amino Acid Dilemma:
The Tale of the Snail
By Douglas B. Sharp
A natural progression from the Miller-Urey experiment creating amino acids in an apparatus where electric sparks zap an atmosphere of water, methane, ammonia and hydrogen gas is to ask the question of whether the same environment is capable of producing viable proteins by assembling themselves.
We will ignore for the moment the multitude of problems with the experiment itself (see http://en.wikipedia.org/wiki/Miller-Urey_experiment for an overview) and assume that the product of the simulation of early conditions of life produced all of the amino acids needed for life. The only question we will deal with in this paper is to isolate one problem out of the multitude concerning the chemical origin of life, that is, that this experiment produces equal mixtures of isomers of amino acids, designated as right-handed or left-handed. Life only uses the left-handed variety. All 20 amino acids that are used in life all exhibit this characteristic except glycine. The left-handed and right-handed isomers react chemically the same, and are virtually impossible to separate. Moreover, when death occurs, the left-handed isomers over time spontaneous reverse into the right-handed variety, a process called racemization.
Early creationists, such as A. E. Wilder-Smith and James F. Coppedge identified this as a major problem for abiogenesis. Coppedge, in his book Evolution: Possible or Impossible took an average length protein of 410 amino acids and calculated that the odds against a protein being formed by chance with every amino acid being left-handed is one chance in 2410 or 10123. This is not taking in account the odds of a specific sequence of amino acids being selected, that’s another problem outside the scope of this one.
Coppedge’s argument, to my knowledge has never been refuted. I remember seeing a large book, proceedings from a conference where papers were being presented trying to find a way to synthesize pure left-handed amino acids, and all met with failure.
How do you quantify a number like 10123 where it can be in terms we can understand? Let’s imagine a snail whose job it is to move the earth to the extreme end of the universe and back one molecule at a time. Furthermore the snail moves at a pace of a millimeter in a million years.
Next, let’s imagine an experiment that produces proteins, all of the right length of 410 amino acids in a quantity of one mole (6.022 x 1023 proteins) every second. The snail will win the race.
Here are the calculations:
The volume of the earth is 1021 cubic meters or 1027 milliliters. Let’s presume that the earth is entirely water for the sake of simplifying our calculations (this actually gives the experiment a slight advantage because the snail will have to take more trips). A mole of water is 18 grams and it contains 6.022 x 1023 molecules. 1 gram = 1 milliliter.
Therefore the earth has 3.345 x 1051 water molecules. To simplify and round up, let’s say the snail has to make1052 round trips.
The edge of the known universe in its most extreme estimate is 20 billion light-years. A light-year is just less than 10 trillion kilometers, so the distance the snail has to travel is 3.8 x 1029 millimeters. To simplify, let’s make it 1030 millimeters. Altogether the snail will travel 1082 millimeters. There are 31,000,000 seconds in a year. Since he travels one millimeter in a million years, it will take approximately 1095 seconds for the snail to complete his task.
If our experiment produces one mole of protein every second it will still take 1099 seconds to produce one viable protein with all left-handed amino acids. Only when our experiment produces 10,000 moles per second do we come to the point where we can catch up to our snail. A mole of polyalanine, with 410 units of amino acids, which would be the simplest protein to experiment with, weighs 36,526.9 grams. So you would have to produce 365,269 kilograms per second to keep pace with the snail. This is over 400 tons per second.
Now suppose by a freak accident, you are able to produce a viable protein. You will need to gather together a sufficient quantity of them to produce life, all which work together in harmony. Furthermore, you need to create DNA, RNA and ribosomes that manufacture them over and over.
If you are investigating the problem of abiogenesis, this is only the start of your journey, the first step in a series of problems that must be solved to create life. This is why the idea of a creator God is a reasonable choice.