Wednesday, 10 September 2014

Reconceptualizing natural selection as primarily concerned with counteracting entropy (e.g. mutation accumulation)

Reconceptualizing natural selection as primarily concerned with counteracting entropy (e.g. mutation accumulation)

Michael A Woodley and I have developed a new conceptualization of the fundamental process of natural selection. It draws on diverse perspectives such as a couple of years of conversations about the cause of decline in intelligence (g) since Victorian times (especially the importance of mutation accumulation due to the massive decline in child mortality rates - http://iqpersonalitygenius.blogspot.co.uk/search?q=mutation), the work of WD Hamilton on the evolution of sexes, Graham Cairns-Smith's work on the origins of life, an old paper of mine on 'endogenous parasitism', recent discussion on the implications of the 'mouse utopia' experiment and more.  



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The essence of the idea is that replication is not the main problem for living entities, indeed replication can be taken for granted.

The big problem for living entities is entropy; the main answer to entropy is natural selection, and the main anti-entropic mechanism of natural selection is massive overproduction of offspring with various means of selectively culling the most entropically-damaged offspring.

In terms of genetics; this could be understood in terms of saying that something like mutation-selection balance is the essence of natural selection

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On Graham Cairns-Smith's conception of life, natural selection is built-into reality – NS is simply a part of the world – certainly part of chemistry (e.g. crystal propagation), probably physics too. In evolutionary terms, there is no dividing line between organic and inorganic, alive and dead.

Therefore, Life (in the sense of replicating entities subject to natural selection) is to be found pretty-much everywhere – not just in biology.

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So the main problem for a living entity is not to make copies of itself, replication can be 'taken for granted' as a kind of universal phenomenon, but the main problem is to counteract entropy.

Entropy, that is to say random damage to replicating entities from many sources and copying errors during replication, is inevitable. Indeed, entropy will tend to degrade any identifiable structure, and any form of organization. Over time, the tendency is for all structure and organization to be returned to randomness.

This means that all lasting structures and all types of organization must overcome entropic degradation.

So, any actually-observable entity has already solved the problem of entropy to the extent that it is indeed observable! Any structured or organized thing which exists has solved the problem of entropy such that it at least came into existence, was sustained long enough to be observable by us, and - unless it is unique - has some mechanism for making more-of-itself: for replicating.

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Furthermore, entropy affects all replication - so there are errors in replication that enter in the transmission of information between parent and offspring.

In a nutshell, this means that there is an unavoidable, intrinsic and cumulative entropic tendency for the fitness of any naturally selected lineage to decline to zero - to extinction, to non-life.

An example of this would be the tendency for mutations to occur in each parent organism, to be transmitted from parent to offspring - with new mutations occurring during the replication process, and for such mutations to accumulate generation upon generation until extinction.

Indeed this is not just additive accumulation, but there is a tendency towards a positive feedback cycle, in which mutations damage functionality which leads to more and additional, and uncorrected mutations.

So, the suggestion is that the fundamental problem for any entity is not replication, but combating entropy.

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One implication is that the basic function of a molecule like DNA is not a matter of achieving replication - because replication would already have been happening, and can be taken for granted; DNA (and its evolution) is primarily about a mechanism of more-accurate/ less error-full replication.

So, the main question for living things is: how is entropy controlled?

And the main answer is: Natural Selection.

The context of Natural Selection (NS) is thus massive over-production of offspring (and spores, seeds, ova, sperm etc), and the strongly-selective reproductive-culling of offspring to eliminate accumulated entropic damage (such as mutations).

Thousands or millions of offspring (etc) may be generated, and selectively eliminated.

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So, the context of the intrinsic decline of fitness in all replicating entities means that the main thrust of evolution by natural selection is simply to maintain fitness - to prevent extinction from intrinsic entropic tendencies - and not to improve fitness, nor to evolve adaptations.

So, this is a Red Queen phenomenon (in which there is running fast just to stay in the same place). Natural selection is necessary to maintain fitness in the face of the entropic tendency for fitness to disappear.

In other words, the phenomenon described as mutation-selection balance is not a specific, contingent, occasional circumstance: but the normal and indeed primary nature of natural selection as it applies to a genetic organism.

The genetics of NS is not primarily about evolving new genes but primarily about preserving from (entropic) destruction what are already-successful genes. It is about preventing the intrinsic tendency towards corruption/ degradation of an already- known-to-be-successful genetic recipe.

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In sum, NS happens in what are ‘already fit’, already replicating, massively-over-reproducing, entities. Lacking which, fitness inevitably regresses to zero.

So – the main thrust of evolution (NS) is to maintain fitness. (A Red Queen sort of thing.)

The usual method for combating entropic damage is massive overproduction of offspring, and therefore Disposable Offspring.

The usual, background situation was that replication was not a problem, and sufficient offspring survival could be taken for granted in the immediate short –term – the problem was the distal long term of a few generations ahead at the point when the tendency was for mutation accumulation to destroy fitness.

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Short term fitness, over the next few generations, was not the major problem - since there was such over-production of offspring; therefore long-term fitness beyond the next few generations is THE major problem.

Therefore, because in this conceptualization, natural selection implicitly looks-forward several generations,  so this is not about the single organism and its fitness but is instead a 'group-ish theory' kind of selection process.

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With such a concept, it is trivially easy for individuals to ‘sacrifice’ their own fitness to some degree, or even the fitness of the immediate next generation or two - when the longer term fitness of the group of descendants is significantly enhanced. (This is a consequence of short-term replication being 'taken for granted' due to the context of massive over-production of offspring.

There is a very low cost to ‘adaptations’ which somewhat lower individual fitness if there is a fitness advantage in the next few generations – because the next few generations are almost guaranteed – they are not the big problem. The big problem is entropy, hence mutation accumulation – and that takes a few generations.

A pay-off two or three generations down the line is therefore almost-directly selected for, in the sense that the short term costs are trivial in the context of massive overproduction and a world of replication-not-a-problem.

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Sexual reproduction was, by this account, relatively easy to evolve; because it enabled better control of entropy (see the work of WD Hamilton - but replacing/ adding to 'parasites' with spontaneously occurring entropic damage), e.g. the purging of mutations, the purifying of the gene pool of second, third etc –generations of offspring.

What gets naturally selected is therefore fitness down-the-line.

In a sense, the proximate locus of natural selection is a few generations ahead; specifically the future generations whose fitness would have declined to zero absent the operations of natural selection.

(This is different from the main emphasis of the conceptualization of mainstream selfish gene theory - which only very seldom allows for the possibility of long-term 'group' fitness advantage overcoming a significant short-term fitness disadvantages. In our view the short-term disadvantages are trivial in effect in a context of 'replication taken for granted' and the usual situation of massive overproduction of offspring.)

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The new conceptualization of NS implies that ‘competition’ with other living things is mainly about preventing the accumulation of entropic damage. Competition with other living things, including other members of the same species, is primarily about the purging, purifying or culling of a large majority of offspring - as the primary method for removing what would otherwise be fitness, lethal accumulations of mutations.

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Note added 11 Sep 2014:

New concept of Natural Selection: RES
1. Replication
2. Entropy
3. Selection

1. Replication is taken as given, 2. entropy tends to degrade structures and organization to stop replication (extinction of lineage), 3. natural selection controls the entropy - lineage is maintained.

By contrast -

Traditional concept of Natural Selection: ERS
1. Entropy
2. Replication
3. Selection

1. Entropy generates variants 2. some of which replicate, and 3. some of these undergo natural selection to expand and create a lineage.

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Note added 18 September 2014

Another way of conceptualizing this is to regard 'mutational meltdown' as a universal process, which always threatens extinction  - and therefore requires mechanisms and process to overcome this intrinsic tendency.

http://en.wikipedia.org/wiki/Mutational_meltdown

Mutational meltdown was first described as a threat for small populations of asexual organisms; later this was widened to sexual organisms and then to large populations - so mutational meltdown has gone from being a specific case to probably a universal possibility.

In effect, I am suggesting that the primary functional necessity for living things is avoidance of mutational meltdown - and all actually observable living things have solved this problem to the extent of their lineage surviving long enough to be observable.
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