Originally published 29 June 1987
At the time Genesis was written, clay was the premier material of artisans. Of it were made containers, tablets for writing, and effigies of animals and men. So what was more natural than for the Creator to do his work in the same medium. According to the author of Genesis, the Lord took up clay into his hands and molded it into the beasts of the field and the birds of the air. And the first man.
If British chemist A. G. Cairns-Smith is right, the story of Genesis may not be far off the mark. Cairns-Smith is the most vigorous advocate for a theory that is gaining increasing support among biologists and chemists: Clay may have been the catalyst that caused life to begin on this planet.
It is widely agreed that all life forms on Earth — bacteria, cabbages, salamanders, and humans — share a common ancestry. We are all made of the same molecular building-blocks; our chemistry is identical; we share a reproductive mechanism based on DNA and RNA molecules. From the point of view of the molecular biologist, the bacterium and the blue whale are more alike than they are different.
By definition, life reproduces — and there are adequate reasons to expect occasional “errors” in the copying process that results in an offspring not quite like its progenitor. Nature selects for survival the “errors” that are most fit. Start with a primary organism, a bacterium for instance, and given enough time the bacterium will evolve into cabbages and salamanders. And into biologists.
It is that first bacterium that is the real problem. No one has yet provided a satisfactory explanation for where that first living cell might have come from. Two theories have been popular: 1) The first organisms arrived on Earth from somewhere else (which merely defers the problem of explaining the origin of life); or 2) the first living organisms happened spontaneously on the early Earth.
Seeking the essence of life
Many experiments since the 1950s have attempted to recreate in the laboratory the chemical and environmental conditions of the early Earth. In these experiments most of the molecular building blocks of life — sugars, phosphates, organic bases, amino acids — have been spontaneously produced. But the creation of the molecules that are the essence of life — DNA, RNA, and proteins — has so far eluded researchers.
To make a protein, smaller amino acid units must link up in a particular sequence many hundreds of units long. As the chain assembles it twists into a helix, like a telephone cord. At the same time the helix folds up into a crumpled cross-linked shape that is determined by the sequence of amino acids. It is the shape of the protein that decides its role in life.
The DNA molecule is another chain of simple sub-units. It is shaped like a spiral staircase. The side rails of the staircase are sugars and phosphates, and the treads are pairs of organic bases. In a typical DNA molecule there are billions of steps on the staircase, and it is the sequence of the steps that is the genetic code.
DNA is the secret to life’s ability to reproduce. The molecule copies itself by unzipping down the middle, with each side strand acting as a template for reassembling its complement. Segments of DNA, with the assistance of RNA, supply the templates for building proteins.
In principle, it’s all chemistry. So why can’t researchers make it happen in the lab? To construct DNA and proteins from non-living matter requires the concentration of raw materials, an input of energy, the removal of water, something to organize the raw materials, and a catalyst — conditions that have proven notoriously difficult to achieve simultaneously. And that’s where clay comes in.
Life from non-life
As long ago as the late 1940s, the chemist J. D. Bernal pointed out that clay is an ideal material to facilitate the synthesis of complex organic molecules. Clay is not just muck; it is a highly-ordered crystalline substance with a surface tendency to attract and hold organic molecules. Clay can serve as a template for organizing organic molecules into long chains. The wetting and drying cycles of clay can transfer energy from the environment to the assembling chains. And clay can shield complex organic substances from the disorganizing influence of sunlight.
Was clay was the catalyst for the first organisms? The chemist A. G. Cairns-Smith thinks so — and he goes even further. He believes the first self-replicating molecules may actually have been filaments of clay, only later replaced by the DNA-like substances they helped to organize.
Life makes life; it happens all the time in every cell. But how did non-life make life? It is one of the biggest questions in biology, and maybe clay holds the answer to the riddle. The chemical reactions that take place on the surface of clay are being vigorously studied at laboratories around the world. It is not inconceivable that at some time in the future life will be a laboratory artifact, fabricated on a bed of clay. The author of Genesis may have had it right.
Cairns-Smith’s clay hypothesis has not received mainstream scientific acceptance, partly due to the difficulty of testing the theory. Cairns-Smith passed away in 2016. ‑Ed.
