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The four mechanisms of evolution

Darwin's finches or Galapagos finches. Darwin,...

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Regular readers of the blog will know of my enthusiasm for evolutionary and developmental theories especially the eight stage evo-devo theory.

I have also advocated the four primary problems faced by all creatures undergoing evolution, as delineated by Theodore Millon– the problems of Existence; Adaptation; Replication and Abstraction which lead to polarities of pain/pleasure;  active/passive; self/other and broad/narrow at each of the stages/domains/ solutions.

However, when we pause to look at what the mechanism of evolution actually is, we clearly note that there are a few prerequisites for evolution to take place and unless all the four mechanisms/ preconditions are present it is unlikely that the creatures will evolve.   I have been having this in the back of my mind for quite some time especially as I  have been ruminating on the BVSR (blind variation and selective retention)  theory of Donald Campbell as applied to creativity.

I was recently reading ‘Driven’ and in that book too a lot of emphasis is placed on the V-S-R (Variation, Selection, Retention) mechanism of evolution. I think this popular portrayal of evolution misses another important ingredient required for evolution that of Struggle due to limited resources and excess fecundity. If the problem of limited resources and excess fecundity was not there, probably there would be no pressure to evolve.


Thus I would like to frame the four evolutionary prerequisites/ mechanisms as Struggle-Retention- Variation-Selection or S_R_V_S.  To elaborate:

1. Struggle: This is driven by the fact of limited resources and overproduction due to excess fecundity. Here two strategies, leading to 2 polarities,  work; one can either compete for resources or one can cooperate and exist symbiotically.  Also, one can either have a r-strategy (low investment in many) of reproduction or A K-strategy (high investment in few). In the eight stage model, the organisms at first 2 levels would be primarily constrained by this evolutionary mechanisms.

2. Retention:  There must exist some mechanism by which the traits that confer survival/reproductive or selection advantage can be retained over time in the same individual and over generations in the same species. Again the mechanism of stable trait over time as well as  over generations may be in conflict with each other and may lead to a polarity. Creatures at stage 3 and 4 of 8 stage evo-devo theory would likely face issues regarding stability and retention of traits; retaining in individual the same trait is an active process; while retaining in generations is more passively driven.

3. Variation. There must exist some  mechanism that causes minor changes in the stable traits such that variation may lead to deleterious or beneficial effect over the individual having that variation. This is classically implemented using mutations and sexual-recombinations. While mutations confer (dis)advantages at an individual level; recombinations take that to the next level by affecting offsprings variability. The creatures at stages 5 and 6 of evo-devo stages are grappling with these problems of adequate variation in self and other.

4. Selection: There must exist some selection criteria based on which the struggling creatures having stable but slightly varying traits can be selected for or against.  While Natural selection (stage 7) employs the three methods of directional, stabilizing and disruptive selection; the stage 8 deploys a qualitatively different method of sexual selection where the criteria for selection may be  arbitrarily driven by choices of the other gender conspesifics.  While the Natural selection criteria is broad, the sexual selection criteria can be said to be narrow. Another way to look at this is that the selection crteria is either to survive (natural selction) or to reproduce (sexual slection) and those who are sucessful can very well move from one level/species to another (speciation due to sexual selection).

To me this is further  corrobrating evidence of the eight stage evo-devo theory and ABCD model being on the right track.


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Posted by on November 19, 2011.

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Categories: evolution

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This blog is an effort of Sandeep Gautam (sandygautam on most social web services) to learn, and at the same time document his journey, and share his knowledge, of psychology and neurosciences, with like-minded folks – a rider is in place at this point: He used to be primarily a software professional (a computer science […]
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