Quantifying the Left-Handed
Amino Acid Dilemma:
The Tale of the Snail
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.