Life Gets Complicated

NAUT2

“In some sense man is a microcosm of the universe; therefore what man is, is a clue to the universe. We are enfolded in the universe”. – David Bohm

The conventional understanding of evolution is that natural selection driven by random mutation accounts for the development of complexity and the diversity of species. Mutations that are detrimental create organisms that will be less likely to survive and create progeny. Mutations that have beneficial effects bestow upon the organisms better survivability and a greater chance the mutation will persist into the next generation. Mutations that are neither beneficial or detrimental may or may not persist; however, a neutral mutation combined with another mutation might produce either a detrimental or beneficial effect. This slow progression of evolution driven by random mutation results in new species. From the earliest single celled organism to humans and whales new organisms and new species arose through chance. This is what Jaques Monod referred to when he said: “Our number came up in the Monte Carlo game.”

This conventional understanding may account for a lot of what happens in evolution. At the same time, it is undoubtedly a vast over simplification of how the diversity of species on our planet has arisen. Life seems to have more strategies at it disposal than waiting for random mutations. And even when random mutations do occur as a part of the evolutionary process, other mechanisms seem to play critical roles in the development of complexity.

An article by George Zimmer in the New York Times shows how complicated evolution can be. The current record holder for the smallest genome is a microbe called Tremblaya princeps. It contains 120 genes and lives in the body of a mealybug. So in a sense it is not an autonomous organism. The mealybug depends on it to metabolize its food and it, in turn, depends on the mealybug for a home. To complicate matter, scientists have now discovered that Tremblaya princeps is not alone in assisting the mealybug with metabolism. There is another microbe named Moranella endobia with 406 genes that helps. So how did the mealybug and these microbes all evolve together? Writes Zimmer:

At some point in the distant past, the ancestors of Tremblaya infected the ancestors of mealybugs. The microbes gave the insects new metabolic powers, allowing them to feed on an abundant substance — sap — that most other insects couldn’t touch. In its comfortable environment, Tremblaya cast off most of its genes.

Only later did Moranella invade the mealybug, and then Tremblaya. It took over some of Tremblaya’s work, opening the way for Tremblaya to lose even more of its DNA, until it was stripped down to a mere 120 genes.

Tremblaya and Moranella are the only bacteria found in a healthy mealybug. But Dr. McCutcheon and his colleagues also found vestiges of vanished microbes — in the mealybug’s own DNA. Some of its genes are more closely related to genes found in bacteria than genes found in any animal.

This strange resemblance means that mealybugs were once host to other species of bacteria, and some of the genes from those mystery microbes accidentally ended up incorporated into their own DNA.

What is apparent from this simple example of the mealybug is that the evolution of the diverse forms of life is not just a matter of random mutation. Life seems to have a variety of mechanisms at its disposal. Sometimes it evolves by assimilating the genetic instruction of other organisms as the mealybug apparently has done. Often it evolves in cooperative environment with other organisms as the two microbes apparently did. The trigger of the change may have been random mutation but the success of mutation was dependent upon the presence of an environment of other organisms. The evolution of the mealybug and the microbes wasn’t so much an evolution by three autonomous species but rather a co-evolution of the three organisms together perhaps with yet more predecessor organisms.

The assimilation strategy used by the mealybug may have also been the strategy that evolved the first complex cells that comprise the forms of life more complex than bacteria. The most primitive cells are called prokaryotes. These organisms, such as bacteria, do not have nuclei or mitochondria, They are basically strands of DNA swimming inside a cell wall. Eukaryotes, organisms with nuclei and mitochondria, are the basis of multicellular organisms. The most accepted theory for how the evolution from prokaryotes to eukaryotes happened is called endosymbiosis. A bacterial organism assimilated another bacterial organism and the resulting symbiosis proved beneficial to both. Eukaryotes did not arise through a mutation in a prokaryotic organism but came about through a merger of organisms. Natural selection played a role after the fact in the result of the merger persisting.

Another strategy life uses can be illustrated with the evolution of multicellular life. The most accepted explanation for this is the colonial theory. Single celled organisms clump together and cooperate through cell-to-cell communication. Eventually cells begin to specialize. There doesn’t necessarily seem to be a mutation required for this to occur. In the laboratory, scientists created multicellular yeast in two months simply by selecting for yeasts that had a greater propensity to clump together. Natural selection, of course, determines whether the multicellular organism is better adapted and survives but the initial multicellular organisms may not have required a mutation. In this case, perhaps genes useful for other purposes or perhaps of no particular value that allowed clumping together of organisms allowed the evolution of what may be a new organism.

799px-ColonialFlagellateHypothesis

What is fascinating in the colonial theory is how single celled organisms once they begin to clump eventually form specialized cells and three dimensional structures. A theory by Stuart Newman on the proliferation of new structural forms among animal life in the Cambrian era suggests that the new animal forms had predecessor structures and forms at the single cell level. “Animal bodies and the embryos that generate them exhibit an assortment of stereotypic morphological motifs that first appeared more than half a billion years ago. During development, cells arrange themselves into tissues with interior cavities and multiple layers with immiscible boundaries, containing patterned arrangements of cell types. These tissues go on to elongate, fold, segment, and form appendages. Their motifs are similar to the outcomes of physical processes generic to condensed, chemically excitable, viscoelastic materials.” (1) Newman goes on to propose that “the origins of animal development lay in the mobilization of physical organizational effects that resulted when certain gene products of single-celled ancestors came to operate on the spatial scale of multicellular aggregates.” (2) In other words, the complex multicellular animals arose by extending and reusing the genes which had already operated at the single-celled level.

In all of these examples the evolution of the new forms of life is not just a matter of random mutation. Life evolves by any and all means at its disposal. It can evolve by assimilating other organisms. It can evolve by cooperating with both like and unlike organisms. It can re-purpose genetic instructions and make remarkable jumps in a short period of time. As I discussed in my previous post, it might even be able to produce new and viable forms by hybridization of different species. Random mutation may still play a big role but it is not the only mechanism at work. Natural selection still determines whether the new organism, whether created by mutation or otherwise, continues.

What is still lacking in this discussion is how the jump was made from inanimate to animate matter. The theory of evolution by natural selection doesn’t try to explain the origin of life, but there remains a big question about the point at which natural selection begins to play a major role in the development of new forms of life. In the Life Before Earth hypothesis, Alexei A. Sharov and, Richard Gordon assume that natural selection was at work perhaps for billions of years before the most primitive one celled organisms appear on Earth. As we saw above the simplest organism is a microbe with 120 genes but even that organism did not evolve by itself nor could it survive by itself. So it is still difficult to determine what could be the minimal organism. There is a big jump from inanimate molecules that can copy themselves to full fledged organisms. For the Sharov and Gordon hypothesis to be correct we would need to believe either that viable proto-organisms with much fewer genes than this could exist or that evolution by natural selection could take place with molecules that are not true organisms.

Just as life has evolved by a variety of strategies, we will likely discover additional mechanisms beyond random mutations were at work during the development of the first life. The strategies used by evolution to create the diversity of species, however, might provide us some insight into how life initially came from inanimate matter.

We can work backward and reason by analogy. We have seen that multicellular organisms arose from clumping of single organisms which begin to fold into a hollow body and develop specialized cells and tissues. A single celled organism is a body enclosed in a cell membrane. Hence, there may have been some unit less than a cell that clumped together and folded in a similar morphological manner to single cells forming multicellular organisms in order to create the initial cells. Interestingly protein folding is itself a key part of proteins forming their three dimensional shapes for them to work properly. Prions, in fact, are misfolded proteins. Nucleic acids also rely on a folding and coiling process. If we had something like a protein(s) folded around a nucleic acid, we might have something like a pre-cellular unit of life. If it clumped together and formed a hollow body, eventually the nucleotide part might separate to form the initial genetic material while the protein part forms a cell membrane. We would have the first cells.

Papilloma-EM_Wiki_200px_hkl_IR

Papilloma virus

A nucleic acid wrapped by a protein is basically a virus. There is still a debate over whether viruses are living or not. The general argument against their inclusion in the living is that they have no ability to reproduce by themselves. They rely on a host organism. The life of a virus is to invade another cell, co-opt its genetic machinery to reproduce itself, then to break apart the cell expelling copies of itself. On the other hand, viruses clearly have abilities to evolve like life. They are truly in-between organisms. Under an electron microscope they resemble inorganic crystals. Much of discussion about viruses and life center around when and how did viruses originate. Since viruses, as we know them, cannot reproduce without other living organisms, some have speculated they originated as organisms that lost their membranes and cellular structure. Others have proposed they originated when pieces of genetic material in cells managed to break out of their cells. Both of these theories, of course, would require that cellular life exist before viruses. A theory by Koonin and Martin proposes a viral origin for life in hydrothermal vents. “Building on the model of Russell and Hall for the emergence of life at a warm submarine hydrothermal vent, we suggest that, within a hydrothermally formed system of contiguous iron-sulfide (FeS) compartments, populations of virus-like RNA molecules, which eventually encoded one or a few proteins each, became the agents of both variation and selection.” (3)

Life might have arisen through some basic folding mechanism that began to work through electromagnetic properties of individual molecules . This folding may be the key to the capture of genetic information. We see this folding at almost all levels of life from proteins, nucleic acids, viruses, single cells, and multicellular organisms. We might even go to a lower level to note that carbon itself, the basis of life, seems to have folding and wrapping ability. The basis of organic life is the ring structure of carbon. Almost every component of life is built by combining ring structures with various substitutions and attachments of other atoms.

Could this folding ability point us to some deep understanding about the nature of reality? David Bohm, a physicist who engaged extensively with J. Krishnamurti, developed a theory that the order we see in the universe is, in fact, an unfolding of some deeper order he called the Implicate Order. “Everything that is and will be in this cosmos is enfolded within the Implicate Order. There is a special cosmic movement that carries forth the process of enfoldment and unfoldment (into the explicate order). This process of cosmic movement, in endless feedback cycles, creates an infinite variety of manifest forms and mentality. Bohm is of the opinion that a fundamental Cosmic Intelligence is the Player in this process; it is engaged in endless experimentation and creativity. This Player, the Cosmic Mind, is moving cyclically onward and onward accruing an infinity of experienced being!” (4)

Folding and unfolding may be the key to understanding life and how the diversity of species and ourselves came to be.

Notes

1- Newman, Stuart. “Physico-Genetic Determinants in the Evolution of Development”. Science 338, 217 (2012);

2- Ibid.

3- http://www.molevol.hhu.de/fileadmin/redaktion/Fakultaeten/Mathematisch-Naturwissenschaftliche_Fakultaet/Biologie/Institute/Molekulare_Evolution/Dokumente/135.pdf

4- http://www.bizcharts.com/stoa_del_sol/plenum/plenum_3.html

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This entry was posted in Human Evolution, Origin of Life, Quantum Mechanics, Randomness. Bookmark the permalink.

2 Responses to Life Gets Complicated

  1. Erik Andrulis says:

    Thanks for sharing this. Glad to hear you’re aware of Bohm. His thinking was quite influential in the theoretical modeling.

    • James Cross says:

      Thanks Erik.

      I hadn’t thought about Bohm for awhile but once I started seeing folding and unfolding at the various levels his idea of the Implicate Order came to mind.

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