Where do we come from?: a humbling look at the biology of life's origin - includes related articles

Cairns-Smith then proposed that these very primitive "organisms" started incorporating short polypeptides (protoproteins) found in the environment - presumably in the soup - because they enhanced the crystals' catalyzing abilities. The road was suddenly open for an increase in the importance of proteins first, and then eventually of nucleic acids, until these two late arrivals on the evolutionary scene completely supplanted their "low-tech" progenitor, and gave origin to the living organisms that we know today.

What is wrong with this picture? First of all, Cairns-Smith seems to completely ignore what a living organism is to begin with. For one thing, crystals don't really have a metabolism, not in the sense defined above for living organisms. The reason for this may have something to do with the fact that not only are crystals structurally much less complex than a protein or a nucleic acid, but also with their silicon-based chemistry, recognizably much simpler than the carbon-based chemistry utilized by living organisms on Earth. The lower complexity and simpler chemistry may be insurmountable "hardware" obstacles to the origination of a true metabolism in clay matter. Second, crystals don't really react to their environment either, another hallmark of every known living creature. Notice that this is a property distinct from metabolism, in that metabolism can be entirely internal, with no reference to the outside world (except for some flux of energy that must come into the organism to maintain its metabolism). On the other hand, living organisms universally and actively respond to changes in external conditions, for example by seeking sources of energy or by avoiding dangers. Furthermore, an argument can be made that crystals are not actually capable of incorporating new information in their inherited "code," unlike what happens with mutations in living beings. True, they can assimilate impurities from the environment and "transmit" such "information" to their "descendants" for some time; but these impurities do not get replicated, they need continually to be imported from the outside, and they do not become a permanent and heritable part of the crystal. Moreover, impurities do not create new types of crystals, the way mutations give rise to entirely new kinds of animals and plants.

Another colossal hole in the clay theory is - of course - that we have no clue to how the "mutiny" of nucleic acids and proteins actually occurred, and in fact we are given very faint hints about how a crystal could possibly co-opt a polypeptide to enhance its growth. Therefore, as much as creationists might like the flavor of a theory of the origin of life in which the first living beings came literally from dust (although Cairns-Smith is certainly no creationist), we're still left with ribonucleo-proteins as our best, albeit fuzzy, option. The origin of life is one question that science will be pondering for some time to come, and skeptics should be wary of oversimplified answers found in introductory biology textbooks.