Jeremiah Keenan | Not a chance, part II

Keen on the Truth | Revisiting the possibility of getting the aaRS protein by chance

By Jeremiah Keenan 10/14/15 12:29am

In my last column, I introduced a small part of why I favor the conclusions of a minority of scientists who are skeptical of materialistic explanations for the existence of biological life. Members of The Daily Pennsylvanian community made incisive comments on both sides of the issue.

One response, quite common in the wider debate over strict materialism, was as follows: Sure, the probability of getting the aaRS is small enough that it wouldn’t have happened on Earth in 4.5 billion years. But the universe is a big place — the dice were being rolled on every conceivable Earth-like planet. Think in terms of the universe, and the statistical problem goes away.

This argument fails when we begin to put numbers to general statements. The observable universe contains an estimated 10 to the 80th electrons. Letting each electron be an amino acid furiously linking and unlinking with its neighbors for 13.5 billion years, still leaves us many orders of magnitude below the expected waiting time for getting a couple of functional proteins. Of course, it is possible that a very large unobservable universe exists, and one could define the boundaries of such a universe to make the numbers work. Such claims are unfalsifiable — but remain more a way of salvaging untenable theories of abiogenesis than providing a reasonable suggestion for how life began.

In a similar vein, some have pointed out that there may be many ways of making life out of matter. The low probability for the one that happened is no more significant than the low probability that, out of millions of college-bound seniors, one particular combination of 2,500 names ended up on Penn’s register this fall.

This suggestion fails to consider that even granted a very large number of ways of making life out of matter, the probability of hitting upon one of them remains negligible as long as there is an overwhelming number of nonfunctional combinations for each functional one.

The analogy about Penn’s register does not apply because there is no “unfunctional” combination of students. To make the analogy relevant we must create such a combination. For example, suppose the first letters of the last names of the Class of 2019, arranged in the order that students confirmed their attendance, turned out to be a recognizable approximation of the opening stanzas of “Hamlet.” This might constitute a “functional” combination of names, and has a ballpark probability similar to that of stumbling upon the entire family of aaRS proteins.

Now, to keep the analogy consistent, we imagine there are many ways of getting “functional” combinations of letters. Just as the aaRS function might arise in any number of different ways, so, too, the 2,500 letters might spell out virtually any conceivable thought. Would this get us into the ballpark of the possible? The answer, statistically, is no. For, though there are an extremely large number of ways to arrange 2,500 English letters into coherent sentences, they remain an infinitesimal fraction of 26^2500.

The same principle applies to achieving a functional system like the aaRS proteins. There may be many ways to achieve such a system. Some of them might not even involve amino acids. But the combinations of amino acids, or other substances, that “work” remain an infinitesimal fraction of a much larger total.

A few commentators brought up the RNA world hypothesis which suggests that the function of the aaRS protein might have been achieved through RNA-based enzymes. There is evidence for the possibility of RNA-based charging of tRNA molecules. Some RNA structures may be capable of self-replication, thus allowing for gradual development of RNA enzymes guided by natural selection.

However, as far as we currently know, the length of RNA needed to act as an aaRS protein is far too great to realistically allow for such self-replication. Thus, the RNA world hypothesis does not solve the overarching problem I articulated with respect to the aaRS protein function. It simply moves the problem from a protein-based system to an RNA-based system.

An increasing number of scientists faced with this and other issues have become skeptical that life arose on Earth by purely materialistic means. Their (and my) position is not a matter — as some imagine — of questioning laboratory science. It’s a rational rejection of an ideological framework that demands life can be explained by chance and Darwinian evolution.

JEREMIAH KEENAN is a College junior from China studying mathematics and classical studies. His email address is jkeenan@sas.upenn.edu. “Keen on the Truth” appears every other Wednesday.

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