In an article here yesterday, I described the thermodynamic challenges to any purely materialistic theory for the origin of life. Now, I will address one of the most popular and misunderstood claims that the first cell emerged through a process that demonstrated the property known as self-organization.
As I mentioned in the previous article, origin-of-life researchers often argue that life developed in an environment that was driven far from equilibrium, often referred to as a non-equilibrium dissipative system. In such systems, energy and/or mass constantly enters and leaves, and this flow spontaneously generates “order” such as the roll patterns in boiling water, the funnel of a tornado, or wave patterns in the Belousov-Zhabotinsky reaction. The assertion is that some analogous type of self-organizational process could have created the order in the first cell. Such claims sound reasonable at first, but they completely break down when the differences between self-organizational order and cellular order are examined in detail. Instead, the origin of life required complex cellular machinery and preexisting sources of information.
The main reason for the differences between self-organizational and cellular order is that the driving tendencies in non-equilibrium systems move in the opposite direction to what is needed for both the origin and maintenance of life. First, all realistic experiments on the genesis of life’s building blocks produce most of the needed molecules in very small concentrations, if at all. And, they are mixed together with contaminants, which would hinder the next stages of cell formation. Nature would have needed to spontaneously concentrate and purify life’s precursors. However, the natural tendency would have been for them to diffuse and to mix with other chemicals, particularly in such environments as the bottom of the ocean.
Concentration of some of life’s precursors could have taken place in an evaporating pool, but the contamination problem would then become much worse since precursors would be greatly outnumbered by contaminants. Moreover, the next stages of forming a cell would require the concentrated chemicals to dissolve back into some larger body of water, since different precursors would have had to form in different locations with starkly different initial conditions. For more details on these problems, see Robert Shapiro’s book on Origins, or the classic book The Mystery of Life’s Origins.
In addition, many of life’s building blocks come in both right and left-handed versions, which are mirror opposites. Both forms are produced in all realistic experiments in equal proportions, but life can only use one of them: in today’s life, left-handed amino acids and right-handed sugars. The origin of life would have required one form to become increasingly dominant, but nature would drive a mixture of the two forms toward equal percentages, the opposite direction. As a related but more general challenge, all spontaneous chemical reactions move downhill toward lower free energy. However, a large portion of the needed reactions in the origin and maintenance of life move uphill toward higher free energy. Even those that move downhill typically proceed too slowly to be useful. Nature would have had to reverse most of its natural tendencies in any scenario for extended periods of time. Scientists have never observed any such event at any time in the history of the universe.
These challenges taken together help clarify the dramatic differences between the two types of order:
- Self-organizational processes create order (i.e. funnel cloud) at the macroscopic (visible) level, but they generate entropy at the microscopic level. In contrast, life requires the entropy at the cellular size scale to decrease.
- Self-organizational patterns are driven by processes which move toward lower free energy. Many processes which generate cellular order move toward higher free energy.
- Self-organizational order is dynamic — material is in motion and the patterns are changing over time. The cellular order is static — molecules are in fixed configurations, such as the sequence of nucleotides in DNA or the structure of cellular machines.
- Self-organizational order is driven by natural laws. The order in cells represents specified complexity — molecules take on highly improbable arrangements which are not the product of natural processes but instead are arranged to achieve functional goals.
These differences demonstrate that self-organizational processes could not have produced the order in the first cell. Instead, cellular order required molecular machinery to process energy from outside sources and to store it in easily accessible repositories. And, it needed information to direct the use of that energy toward properly organizing and maintaining the cell.
A simple analogy will demonstrate why machinery and information were essential. Scientists often claim that any ancient energy source could have provided the needed free energy to generate life. However, this claim is like a couple returning home from a long vacation to find that their children left their house in complete disarray, with clothes on the floor, unwashed dishes in the sink, and papers scattered across all of the desks. The couple recently heard an origin-of-life researcher claim that order could be produced for free from any generic source of energy. Based on this idea, they pour gasoline on their furniture and then set it on fire. They assume that the energy released from the fire will organize their house. However, they soon realize that unprocessed energy creates an even greater mess.
Based on this experience, the couple instead purchase a solar powered robot. The solar cells process the energy from the sun and convert it into useful work. But, to the couple’s disappointment the robot then starts throwing objects in all directions. They look more closely at the owner’s manual and realize they need to program the robot with instructions on how to perform the desired tasks to properly clean up the house.
In the same way, the simplest cell required machinery, such as some ancient equivalent to ATP synthase or chloroplasts, to process basic chemicals or sunlight. It also needed proteins with the proper information contained in their amino acid sequences to fold into other essential cellular structures, such as portals in the cell membrane. And, it needed proteins with the proper sequences to fold into enzymes to drive the metabolism. A key role of the enzymes is to link reactions moving toward lower free energy (e.g. ATP → ADP + P) to reactions, such as combining amino acids into long chains, which go uphill. The energy from the former can then be used to drive the latter, since the net change in free energy is negative. The free-energy barrier is thus overcome.
However, the energy-processing machinery and information-rich proteins were still not enough. Proteins eventually break down, and they cannot self-replicate. Additional machinery was also needed to constantly produce new protein replacements. Also, the proteins’ sequence information had to have been stored in DNA using some genetic code, where each amino acid was represented by a series of three nucleotides know as a codon in the same way English letters are represented in Morse Code by dots and dashes. However, no identifiable physical connection exists between individual amino acids and their respective codons. In particular, no amino acid (e.g., valine) is much more strongly attracted to any particular codon (e.g., GTT) than to any other. Without such a physical connection, no purely materialistic process could plausibly explain how amino acid sequences were encoded into DNA. Therefore, the same information in proteins and in DNA must have been encoded separately.
In addition, the information in DNA is decoded back into proteins through the use of ribosomes, tRNAs, and special enzymes called aminoacyl tRNA sythetases (aaRS). The aaRSs bind the correct amino acids to the correct tRNAs associated with the correct codons, so these enzymes contain the decoding key in their 3D structures. All life uses this same process, so the first cell almost certainly functioned similarly. However, no possible connection could exist between the encoding and the decoding processes, since the aaRSs’ structures are a result of their amino acid sequences, which happen to be part of the information encoded in the DNA. Therefore, the decoding had to have developed independently of the encoding, but they had to use the same code. And, they had to originate at the same time, since each is useless without the other.
All of these facts indicate that the code and the sequence information in proteins/DNA preexisted the original cell. And, the only place that they could exist outside of a physical medium is in a mind, which points to design.
Photo credit: Jean Beaufort, via PublicDomainPictures.net.