Clenes and Genes: Evolution of clay and the genetic takeover

This post is heavily based on Tim Tyler's page. It has lots of dead pictures, so view them on the Internet Archive if you see them.

Genes are not the only thing that can copy themselves. Computer virus, RNA, protein virus (prion), and chain mails, they all can.

The idea of non-gene replicators is not new. Richard Dawkins proposed memes in The Selfish Gene (1976), and Graham Cairns‑Smith proposed clay-genes (clenes?) in The origin of life and the nature of the primitive gene (1966). Genes and memes are getting all the popularities, but clenes aren't, so I'll summarize clene theory. A detailed explanation is here.

Overview of clenes and genes

First we check the 1966 paper's abstract:

Life on earth evolved through natural selection from inorganic crystals.

During the formation of a crystal, certain kinds of lattice imperfections usually replicate as a necessary part of the crystallization process.

... the primitive genographs were patterns of substitutions in colloidal clay crystallites. (The theoretical information density in such a crystallite is comparable to that in DNA.)... A gradual “take-over” of the control machinery by organic macromolecules—a genetic metamorphosis—is then considered to have occurred.

Note: Cairns-Smith calls any kind of gene-like replicator as "genographs" ("gene-pictures").

From this site:

Clay, like any silicate, is made up of crystals. Crystals can grow and accumulate out of solutions, and generally once a crystal formation starts to take on a shape, it continues to grow along that same pattern.

That allows heredity.

Say, for example, you have two different crystal patterns, one of which results in a stickier clay that has more or better ways to get stuck on other substances. If a landslide or other geologic activity dumps a sample of each into a river, the non-sticky crystals wash out to the ocean and are lost. The sticky ones catch on the riverbank, and start accumulating and growing, thus building up into a clay deposit. Then a dry season hits, and the river lies empty for a while. The clay dries out, cracks, and is blown by the wind. Most of these airborne flakes still have the same microscopic crystalline structure as the original deposit. They then land in other waters, accumulate and form more clay beds based on the same crystalline structure.

That gives selection and replication.

There's no mention of mutation, but it's easy to imagine that a bit of randomness makes the replicated clay somewhat different. That's mutation. That's all you need for natural selection.

From Wikipedia:

By simple, inorganic, physical processes—a selection environment might exist for the reproduction of clay crystals of the "stickier" shape.

Step 1: evolution of sticky clays.

There follows a process of natural selection for clay crystals that trap certain forms of molecules to their surfaces that may enhance their replication potential.

Step 2: sticky clays develops organic technology, such as sticky RNA molecules.

Complex proto-organic molecules can be catalysed by the surface properties of silicates.

Step 3: organic technology takes on a life of its own.

When complex molecules perform a "genetic takeover" from their clay "vehicle", they become an independent locus of replication.

Step 4: organic molecules takeover the replication process, and clays fall into irrelevance.

How clay life could work

Clay life must have some information, clene, stored in some physical medium. This medium is the crystal structure. Clay life reproduces by snapping in half.

1D clene would be stored in the layer structure of clay.

Basically, clay cracker sandwiches.

The structure reproduces by growing on its sides, creating a big multilayered clay sandwich. It reproduces by snapping off the sides. Even if it doesn't snap off, the edges with a better mutation would grow faster, thus letting natural selection kick in without snapping off.

2D clene would be to stored on the face of a growing needle.

2d clene reproduction

Basically, like colored toothpaste. Its growth is like squeezing the toothpaste.

How organic molecules started piggybacking on clay life

We'll consider only 2D clene life for now. Material taken from here.

Clay life will die if it can't keep itself together. Clene cannot persist if it keeps mutating into noise. This is the general phenomenon of error catastrophe: a species goes extinct if its replication is too error prone.

Most crystals have some tendency to grow in all directions... A crystal organism that grows using a screw dislocation can arrange itself so that growth only occurs in one direction - and growth in other directions requires surface-nucleation to happen...

When crystals break, their crystalline structure can be stressed at the point of the break, causing defects... Practically any mechanical stress can produce mutations. 

It needs protection. Organic molecules are a good way to protect itself. They are tough and sticky, and can be stuck to the surface of a growing clay needle.

We propose here that clay organisms came to contain grooves designed to act as catalytic surfaces synthesizing and retaining polysaccharide chains. They did this mainly for protection against physical disturbance - and to avoid the mutational force represented by sideways growth - which otherwise threatens to obliterate them.

Long organic molecules in the surface grooves of a clay life

How the takeover could have happened

At first, it was a good cooperation.

The clay genes find the organic genes useful, and the organic genes can't reproduce without the clay ones at all - at least not until they can produce a whole family of fancy enzyme-like structures to catalyse their own replication.

But not forever. Clay replicators were a necessary bootstrapper for organic replicators. Organic molecules are tough. They don't assemble easily on their own. Organic polymers naturally form sticky tars, not self-organising structures. However, once they come into existence, organic genes can perform all the other functions performed by clay genes much more efficiently.

Organic molecules are better for "high tech" machinery. This is mainly because the atoms in them are held together more securely... By contrast a crystalline structure formed from water solutions is always in danger of dissolving away again in water; and very small crystals, or small pieces of crystal are particularly liable to fall apart or re-arrange. It is the other side of the same coin: if you can self-assemble easily, you can self-disassemble easily too.

Eventually, organic genes developed all the mechanisms necessary for its own replication, and no longer need the help of clay. They have achieved reproductive independence.

It might have seemed like a small step to have introduced those first crudely-replicating polymers, but it was fatal to the whole clay system. In any competition between organic and inorganic control systems, the organic ones would be almost bound to win in the end - because metastable structures can be engineered more finely with the use of organic molecules. Anything clay could do organic molecules would eventually come to do better.

Other things that Graham Cairns-Smith did

He was a chemist.

He wrote a book about consciousness. Evolving the Mind: On the Nature of Matter and the Origin of Consciousness (1998). Geez. Everypony wants to solve consciousness these days...

Daniel Dennett gave a review here. I don't think it's worth reading though. Basically, his theory is that consciousness involves some kind of quantum mechanical stuff, but isn't convincing in what that stuff would actually do.

Another takeover?

Tim Tyler's presentation is here.

Today, billions of years later, another change is under way in how information passes from generation to generation. Humans evolved from organisms defined almost totally by their organic genes. We now rely additionally on a vast and rapidly growing corpus of cultural information generated and stored outside our genes - in our nervous systems, libraries, and, most recently, computers.

Our culture still depends utterly on biological human beings, but with each passing year our machines, a major product of the culture, assume a greater role in its maintenance and continued growth. Sooner or later our machines will become knowledgeable enough to handle their own maintenance, reproduction and self-improvement without help. When this happens the new genetic takeover will be complete.

There remains a few possibilities left for humans:

1. Destroy themselves so fully that the machines would never rise.
2. Merge with the machines and leave the organic chemicals fully behind, and use silicon life instead.
3. Become overcome by the machines, like the clays who were overcome by the organics.

What shall it be? I say it's a race between all of them. I personally don't care. As long as this human business can end one way or another!