A fantastic article at Universe Today reports on “The Improbable Origins of Life on Earth.” It opens with a striking admission of our ignorance about how life arose:

We do not yet know how, where, or why life first appeared on our planet. Part of the difficulty is that “life” has no strict, universally agreed-upon definition.

The author is Paul Sutter, an astrophysicist at Ohio State University — and he’s absolutely right: there’s presently no natural explanation for the origin of life. 

What Is Life?

Sutter provides some useful definitions of life, starting with what he calls a “simple statement”:

Life is that which is subject to Darwinian evolution. That is, life experiences natural selection, that unceasing pressure that chooses traits and characteristics to pass down to a new generation through the simple virtue of their survivability.

If we accept this definition at face value, life must be highly complex. That’s because Darwinian evolution requires both survival and replication. Survival requires the ability to metabolize materials from the surrounding environment into energy needed to power the chemical reactions of life, and replication requires the ability to make copies of yourself with some minimal level of fidelity. Both of these requirements entail highly complex systems.

Here’s how Walter Bradley and I described the minimal complexity of life in our chapter “Did Life First Arise by Purely Natural Means?” in The Comprehensive Guide to Science and Faith, published in 2021:

[A]ll living systems (1) process energy, (2) store information, and (3) replicate. In nature, these processes are performed primarily by molecules from three families of large biopolymers: proteins, DNA, and RNA. The mystery of how life began is essentially the mystery of how these three types of biopolymers formed and congregated within a cell with a barrier made of lipids as a self-replicating system.

Sutter seems to unwittingly agree with this description of life, because he then elaborates on what is necessary to make Darwinian evolution possible, and lands on exactly the same three requirements for life (though listed in a different order):

To succeed at evolution and separate itself from mere chemical reactions, life must do three things. First, it must somehow store information, such as the encoding for various processes, traits, and characteristics. This way the successful traits can pass from one generation to another.

Second, life must self-replicate. It must be able to make reasonably accurate copies of its own molecular structure, so that the information contained within itself has the chance to become a new generation, changed and altered based on its survivability.

Lastly, life must catalyze reactions. It must affect its own environment, whether for movement, or to acquire or store energy, or grow new structures, or all the many wonderful activities that life does on a daily basis.

Again, this is exactly right. And doing these “three things” — “store information,” “self-replicate” and “catalyze reactions” — isn’t simple. The whole process requires complex DNA and RNA molecules and molecular machines. Sutter appreciates this fact and gives a decent sketch of the complexity of life:

[L]ife on Earth has evolved a dizzying array of chemical and molecular machines to propagate itself — a menagerie so complex and interconnected that we do not yet fully understand it. But a basic picture has emerged. Put exceedingly simply (for I would hate for you to mistake me for a biologist), life accomplishes these tasks with a triad of molecular tools.

Sutter is correct that life is full of molecular machines and that we’re still untangling its complexity. And the molecular triad he refers to is composed of DNA, RNA, and proteins. 

The Molecular Triad of Life

Regarding DNA, he says strikingly that, “The raw ability of DNA to store massive amounts of information is nothing short of a miracle.” 

Regarding RNA, Sutter says that it “stores information but, again speaking only in generalities, has the main job of reading the chemical instructions stored in the DNA and using that to manufacture the last member of the triad, proteins.” Of course he’s right that RNA stores (and transports) information that is used in manufacturing proteins, but I would argue he understates its other important functions. As we recently discussed, we can now identify “RNA genes” which produce RNAs as an end in themselves that perform numerous important cellular functions. 

As for proteins, Sutter provides a nice summary of their importance and their diversity:

“Proteins” is a generic catch-all term for the almost uncountable varieties of molecular machines that do stuff: They snip apart molecules, bind them back together, manufacture new ones, hold structures together, become structures themselves, move important molecules from one place to another, transform energy from one form to another, and so on.

But there’s a catch: proteins are also necessary for replicating DNA. Sutter explains: “DNA stores information, RNA uses that information to manufacture proteins, and the proteins interact with the environment and perform the self-replication of DNA.” 

The Irreducible Complexity of Life

But then Sutter closes with a powerful conclusion that the “interconnected” nature of this triad means that all aspects of the system must be present for life to function:

The interconnected nature of DNA, RNA, and proteins means that it could not have sprung up ab initio from the primordial ooze, because if only one component is missing then the whole system falls apart — a three-legged table with one missing cannot stand.

This almost sounds like a description of “irreducible complexity” — if “one component is missing then the whole system falls apart.” And once again, he’s absolutely right: Life as we know it requires DNA, RNA, and protein to function, and it can’t arise in a stepwise manner on the early earth.

A Potent Challenge to Chemical Evolution

What about his comment that life’s “interconnected nature” means “it could not have sprung up ab initio from the primordial ooze”? That sounds like a potent challenge to chemical evolution. 

Now make no mistake, Sutter clearly endorses evolution at multiple points in his article, and I have no idea what he thinks about intelligent design. And while he thinks that life “could not have sprung up ab initio from the primordial ooze,” it’s not entirely clear if that wording is intended to leave the door open to some other unspecified types of models for a natural origin of life. Nonetheless, his arguments here about obstacles to a stepwise explanation of chemical evolution — even alluding to the irreducibly complex nature of life’s fundamental biomolecules — are exactly right. 

It’s good to find another scientist — with no connections to intelligent design — who sees the issue so clearly