Abiogenesis: A Problem of Origins (part 2)

(Part 2 in a 3 part series)

Making Bricks

Granted, life is complex, but what is so impossible about starting life if you've got plenty of time and materials at your disposal? After all, didn't we once have a seething prebiotic soup covering our planet? Weren't the oceans a rich primordial ooze teaming with exotic chemicals derived from a mix of an alien atmosphere, abundant lightning, and solar energy? And isn't our planet billions of years old? Time plus chance are a dynamic duo. So, what's the problem?

The problem is with all of the assumptions.

The first flaw is in the myth of the prebiotic soup. The idea of a chemical "soup" is not a product of geological evidence, it was merely assumed based on its theoretical need. In order to build a thing you first need the materials with which to build it, and since life (or any meaningful precursor to it) is such a complex thing, you need a lot of materials jostling around for chance to do its work.

Unfortunately, there is no compelling evidence that our oceans, or the atmosphere with which it might interact, had the necessary composition to produce even the building blocks of the cell. It was assumed that the early earth had a "reducing atmosphere," (hydrogen, methane, ammonia, water vapor) which would enable the creation of the essential components. Instead, the evidence indicates that it was a mix of carbon dioxide, nitrogen, and water vapor. There are also many strong indications that free oxygen has been present even from before the appearance of life. This would be a substantial problem in that oxygen is destructive to the molecules necessary to assemble biological life. And the greatest irony is that water — which is so necessary for life — actually interferes with the assembly of certain of these building blocks.

Regardless of the state of the earliest atmosphere, there was an extensive period of Earth's history that was unavailable for the formation of life, or at least its survival. This is due to the continual bombardment of the earth by pre-planetary materials, the scars of which can still be seen on our moon. The largest of these would have sterilized any life that might have formed, and such events did not dwindle until approximately 4 billion years ago. The interesting thing is that the earliest geological records have life arriving on the scene shortly after this time. The long period of time necessary to allow chance to work its magic has evaporated. In the words of Steven Jay Gould:

We are left with very little time between the development of suitable conditions for life on the earth’s surface and the origin of life. Life is not a complex accident that required immense time to convert the vastly improbable into the nearly certain. Instead, life, for all its intricacy, probably arose rapidly about as soon as it could.

And paleontologist Niles Eldridge goes a step farther in saying that

There is now overwhelmingly strong evidence, both statistical and paleontological, that life could not have been started on Earth by a series of random chemical reactions.... There simply was not enough time... to get life going.

But let's assume for the sake of argument that all the conditions did happen to be just as they had hoped. What is it that might be produced? Well, according to the famous Miller-Urey experiments, when energy is added to the chemical mix (hydrogen, methane, ammonia, water vapor) certain essential molecules are produced. Most notably, these include amino acids, which are the building blocks of proteins. And proteins are some of the most important and abundant components of the cell. This was an exciting step for origins of life research. Unfortunately, it was only a token victory.

First of all, it should be noted that proteins are made up of some 20 different amino acids, and not all of these were formed in these or subsequent experiments. Second, the energy needed to assemble amino acids is as likely to destroy them as form them, so the experiment itself must carefully take this into account. This means that the results of the experiment were a matter of human engineering — intelligent design. Third, in the presence of oxygen, there would be no results to speak of and, as stated earlier, there is substantial evidence that oxygen was present in the early atmosphere and oceans. Fourth, even though some desirable molecules were present, the vast majority of what was produced was an insoluble tar-polymer. So, to yield enough amino acids in our oceans to give "chance" a fighting chance would also mean the existence of an enormous amount of tar, which would in turn leave a distinct signature in the fossil record. There is no trace of such a thing, nor is there evidence of any other biotic precursor or byproduct in the geological strata prior to the sudden appearance of cellular life.

But again, let's assume for the sake of argument that all the essential amino acids can be formed by natural processes. We still have the problem of building proteins from these, and as theoretical physicist and astrobiologist Paul Davies said:

Just as bricks alone don't make a house, so it takes more than a random collection of amino acids to make life. Like house bricks, the building blocks of life have to be assembled in a very specific and exceedingly elaborate way before they have the desired function.

If amino acids are like bricks from stirred mud, then proteins are like mansions from stirred bricks.
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Part 3