The Internal Evolutionary Mechanism "Stationary Phase Mutations" to the "Baldwin Effect" © John Latter 2001   Bookmark/Add To Favourites?

Index:

1) Introduction
2) The Post-Notochord Model
3) The Bacterial Model
4) Comparison of the two Models
5) Evolutionary History
6) Method of Testing
7) Conclusion

1) Introduction [Return to Index]

   "In 1988 a minor collision occurred between natural reality and evolutionary theory when an article entitled "The Origin of Mutants" [1] appeared in Nature Magazine. The authors (Cairns et al.) reported experiments in which advantageous mutations in bacteria appeared to have happened with a greater frequency than conventional theory could account for. Subsequent experiments producing similar results have been performed by other scientists one of whom, Barry Hall, has said "Mutations that occur more when they`re useful than when they`re not: that I can document any day, every day, in the laboratory" [2]."

    The above is the opening paragraph from an article [3] comparing the reception given to the described phenomena (originally called "Directed Mutation" but now more often "Stationary Phase" or "Adaptive Mutations") and that accorded Galileo's Heliocentric Theory. In another article that appeared in New Scientist [4] David Thaler, then of Rockefeller University, is quoted as saying "In evolutionary theory there has been an overemphasis on the power of selection as opposed to the generation of diversity. Maybe this [the phenomena of stationary phase mutations] will take it to another level". In addition to providing a link between stationary phase Mutations and the Baldwin Effect the following also attempts to bridge their gap with Darwin`s principle of Natural Selection.

   Like all organisms bacteria are naturally integrated and though there is an apparent diversity of results in experiments that have produced stationary phase mutations there are also indications they may be due to a single mechanism triggered by varying degrees of disturbance to homeostasis [5]. It is proposed that such a mechanism existed in the single-cell common ancestor and that when life became multi-cellular so did the mechanism.

   To convey the simplicity of the concept the proposed mechanism is initially presented (as a "fait accompli") for organisms that have evolved beyond the notochord stage and a description given of how it would account for the Baldwin Effect. It is then used to explain the phenomena of stationary phase mutations in bacteria and in doing so shows, as one would expect of a mechanism based on homeostasis ("staying the same"), how similar the basic mode of operation is for both cases. Next, on the stated assumption that the proposed mechanism also existed in the single-cell common ancestor, evolutionary history is looked at for supporting evidence and this ranges from the comparative sequencing of protein amino acids to evolution of the brain. The premise underlying the proposal is that the nature of life is simply to Be and continuity of Being is maintained in a state of inner equilibrium.

    The basis on an extension to homeostasis means that the proposed mechanism is testable and the appended (generic) Method of Testing is currently illustrated by two experiments that inadvertently met it's criteria. Finally the proposed mechanism is used to account for "problem areas" of current theory such as the Common Origin of the Pentadactyl Pattern in both the Fore and Hind Limbs of Terrestrial Vertebrates.

2) The Post-Notochord Model [Return to Index]

   

The diagram opposite shows a dotted area within which all internal and external "inputs" come together and it is here that an internal evolutionary mechanism is proposed to exist. Cannon (1929) formulated the concept of "homeostasis" whereby activity at this level can be described as "self regulating" or "automatic" which are observations of a closed system made from an external standpoint. The model proposes, when viewed from the inside, any non thinking and non intelligent organism with such a configuration is simply maintaining equilibrium and that this equilibrium extends in another direction - that of evolution.      The dotted area, arbitrarily labeled the A.O.N.E. ("Area of Natural Equilibrium"), is a localized area at the apex (or center) of the internal homeostatic hierarchy [Note 1: The Triune Brain]. The genome in such an organism's germ cells, equally hierarchically integrated, will also have a localized area and this connectivity reflects the continuity of organism - genome - organism.

     Changes in the life experiences of an organism as 'experienced' at the level of the AONE - not that of consciousness - may cause single or co-ordinated evolutionary/devolutionary changes to occur if existing thresholds are exceeded, or just as importantly, not met. These 'changes', transmitted to germ cells, would then cascade down (or radiate outwards) from their localized areas into the genome, and in a direction that would begin (or achieve) restoration of equilibrium in the next generation(s).

    Signalling pathways from outputs of the AONE into the genomes of specific physically remote cells are known to exist as is a molecular mechanism, recently discovered in mammals, of a type that would also be necessary: "Experiments performed at the University of Maryland Medical Center have revealed a molecular mechanism that may be a significant driver of evolution in humans and other mammals. Certain retrotransposons - bits of DNA able to copy themselves from one region of the genome to another - are able to pick up flanking genetic sequences and then insert themselves and the tag-along DNA at new locations" [6]. Connect signalling pathways with such molecular mechanisms and the proposed action of the AONE on the genome is entirely possible.

   This brings to the fore, however, Weismann`s accepted theory that information gained by somatic cells cannot be transmitted to the germ cells that give rise to succeeding generations (the "Weismann Barrier). The proposed mechanism doesn`t contradict this because no direct connection between somatic and germ cells is suggested and illustrating this point is how the effect named after Weismann`s contemporary, J. Mark Baldwin, could be accounted for:

   In 1896 the paper "A New Factor in Evolution" was published by American Naturalist [7] in which Baldwin, referring to his earlier publications, argued the case for a new factor that he called "Organic Selection". The "Baldwin Effect", as it is now more commonly known, says that the phenotypic plasticity of an organism (the ability to adapt to it`s environment) enables it to learn and that over succeeding generations a learned behaviour may eventually become instinctive (i.e. hereditary). Consider the following hypothetical example:

   As a human being learns the complex movements of riding a bicycle the inner co-ordination required is transferred into the cerebellum, a structure within the AONE, so that the activity then appears to be "automatic" and requires less conscious effort. In the cerebellum the desire to ride a bicycle obviously has no relevance and instead it is the overall ability of the non-intelligent organism to balance that becomes significant. If succeeding generations of human beings not only learned to ride bicycles but began doing so for greatly increased periods then any transient disruptions the activity produced in the AONE would be integrated during this time.

   Once existing thresholds were exceeded (see the experiment involving rats in the Method of Testing for a gross example of this happening) co-ordinated evolutionary changes would be triggered in a direction that would restore equilibrium. From an external viewpoint this would be perceived as a relative improvement in the ability of human beings to balance that would be independent of any specific activity.

   In addition once the hypothetical evolutionary changes were triggered they would continue to completion (i.e. restoration of equilibrium) even if the causing factor of riding bicycles were discontinued during the number of generations that such changes would require. One final point: the phenotypic plasticity of human beings is such that if the above example ever were to happen then there wouldn`t be an instinctive urge to ride bicycles but rather an instinctive recognition that it could be done, even if a human being on a bicycle had never been seen before.

   Homeostasis is the maintaining of equilibrium varying about a mean. If the above example is seen as a "positive" upset to equilibrium that would result in a relative improvement in the ability to balance then equally important are "negative" upsets the principle of which can be seen in this example:

   Although there are obvious difficulties in talking about single structures within a naturally integrated organism there existed earlier in Man's evolutionary history an ancestor whose tail provided a naturally utilized input into the AONE of that time. As the transition from ancestor to Man began (irrespective of elapsed time and externally identifiable intermediary stages) the tail began to be used less and less and once the degree of usage no longer reached the lower threshold of the AONE then devolution commenced.

   The reason this occurred is because equilibrium of the AONE would have been upset in a negative direction. Not meeting the lower threshold would be like waiting for a telephone to ring that no longer does (hardly scientific but neither is natural life and it does convey the concept rather well) and so the tail would have been partially devolved but only to a point that restored equilibrium of the AONE.

   This in turn set a new and lower threshold which, when it too was no longer reached, then caused the process to be repeated etc. until today a tail only exists for a short period of time during the growth of the human fetus. This reflects its integrated "position" within our current AONE. The transitory appearance of gills in the human fetus or even the appendix could serve equally well as examples.

   Other examples of phenotypic plasticity include the abilities to tan and  form calluses. The Lamarckian Calluses of the Ostrich looks at an example where calluses have become hereditary and emphasises how the proposed mechanism could explain why the callus on the ankle of the ostrich, the one that is no longer "necessary", is still there. The AONE is ideally placed to have differentiated between those large areas of skin requiring a hereditary degree of pigmentation and the smaller ones requiring calluses or the need to be relatively thicker (e.g. the soles of feet).

   Taking all the examples into account, and putting it in more general terms, the proposed mechanism has the potential, when looking at evolutionary history, to "put the right variations in the right place at the right point in time".

[Note 1:] Maclean's Triune Brain theory [Link 1] [Link 2] considers the human brain to consist of three parts ('reptilian', 'old mammalian', and 'new mammalian') which:

"appear, one after the other, during the development of the embryo and the fetus (ontogenesis), recapitulating, chronologically, the evolution of animal species (phylogenesis), from the lizards up to the homo sapiens."

A person in a coma demonstrates that the intellect is not required for biological survival and so an 'egocentric' view of the human organism may not be appropriate.  [Return to text]

References:

[1] Cairns, Overbaugh and Miller (1988), The Origin of Mutants, Nature 335: 142-145 [Abstract: subscription required]
    http://www.nature.com [return to text]

[2] Corliss (1990), Hypermutation rather than Directed Mutation?, Science Frontiers (secondary source)
     http://www.knowledge.co.uk/frontiers/sf072/sf072b06.htm  [return to text]

[3] Latter (1999), Directed Mutation and Galileo
     http://members.aol.com/jorolat/direct.html [return to text]

[4] Beardsley (1997), Evolution Evolving, Scientific American Sept 97
     http://www.dhushara.com/book/evol/evev.htm [return to text]

[5] Latter (1999), Stationary Phase Mutations and Homeostasis
     http://members.aol.com/jorolat/spmah.html  [return to text]

[6] Hoke (1999), Evolutionary Molecular Mechanism In Mammals Found
     http://unisci.com/stories/19991/0305993.htm  [Internet Archive] [return to text]

[7] Baldwin (1896), A New Factor in Evolution
     http://members.aol.com/jorolat/baldwin2.html  [return to text]

The following are some of the original notes that can now be discounted (they will be expanded upon and incorporated elsewhere).

b) Mole [Return to Index]

     At one point in its evolutionary history the proto-mole presumably ran around on the surface in a similar manner to other small mammals and then, in response to unknown changes in the world, began to live underground. Imagine being a mole who has started to dig a hole, what would be one of the first things you do as your head disappears into the ground?. Close your eyes to keep the dirt out.

     The effect of such a persistent change of behavior would, at a simple level, be two-fold. First the large input of the optic nerve to the AONE would be reduced while that from the muscles keeping the eyes closed would be increased. Intuition suggests that for the lower threshold of the eye not to be attained would be a significant event but once it had happened subsequent devolution would then have been rapid. Evolution of the muscles to replace the eye would have continued a pace in a way that ensured the equilibrium of the AONE was always maintained.

  c) Bacteria [Return to Index]

This sections will soon be replaced by stationary phase mutations

     Bacteria are often described as being "drug resistant" when they have developed immunity to a particular pesticide. When the pesticide is first introduced the physical constancy of the bacteria's world changes upsetting its AONE and either the ability to evolve and restore equilibrium within the new environment exists or it does not. If it doesn't then the bacteria dies but if it does - perhaps because of a "partial dose" -  then continuity of Being is maintained in a new state of equilibrium reflecting the external existence of the pesticide.

     Removing the pesticide again changes the physical constancy of the world and again the telephone doesn't ring. Experience of the pesticide no longer occurs and the bacteria may revert to it's former state of equilibrium reflecting only the environment within which it exists. At no point is the bacteria in a state of "resistance".

4) Molecular evidence [Return to Index]

   The above diagram reflects the fact that some of the single-cell Common Ancestors eventually evolved into fish and some fish eventually evolved into amphibians etc. etc.. It also highlights - when looking at the History of Life relative to the Common Ancestor - that the development of the AONE has been hierarchical in nature.

   If, for example, we consider the sequence "fish - amphibian - reptile" then the Model says that the fish AONE evolved into the amphibian AONE and then into the reptilian AONE. This is, of course, exactly the same as the traditional evolutionary sequence but now the Model indicates something else entirely.

  In saying that evolutionary changes occur because of what happens at the level of the AONE it follows that these changes filter downwards into the organism in order to maintain the equilibrium within it. At the molecular level, therefore, one would not expect to find evidence of the external sequence "fish - amphibian - reptile" but evidence of the internal hierarchical development of the AONE. Anyone familiar with the comparative sequencing of protein amino acids will know that the relationships are hierarchical and not sequential. Some of the data appears to give a further insight to the nature of the AONE and will also be expanded upon at a later date.

  Though the genome hasn't been mentioned it can already be seen that the hierarchical development of the AONE makes perfect sense of the existence of pleiotropic genes etc. etc..