Re: The evolution of "evolution"

From: Dace (
Date: Mon 10 Oct 2005 - 21:56:31 GMT

  • Next message: Scott Chase: "Re: The evolution of "evolution""


    > - --- Dace <> wrote:
    > > I make
    > > it plain in my article
    > > that such mutations merely provide the raw material
    > > for natural selection.
    > > The question is the source of the variations
    > > environmentally selected.
    > >
    > Provision and source are one and the same here.
    > Mutation provides variation and it is a source.

    Mutation is a source of variation, but is it the only source? What about the life experiences of plants and animals? That doesn't count for anything?

    > > Is
    > > it random mutations in our nuclear "determinants,"
    > > as Weismann claimed, or
    > > is it the adaptations made by creatures in the
    > > course of their lives, as
    > > Darwin claimed? Clearly, the second accords better
    > > with common sense. A
    > > theory that can account for transmission of acquired
    > > adaptations is
    > > inherently more plausible than Wiesmann's
    > > alternative.
    > I think you're getting confused about two separate
    > phenomena. There's variation and there's a selection
    > process resulting in adaptation(s).

    I've given no indication that I take variation and selection to be somehow one and the same. My point is that the source of variation-- to be acted on by natural selection-- is primarily the intelligent decisions made by creatures. As Darwin pointed out, animals have a great deal of flexibility in their youth and can re-mold their traits. He speculated that young flat-fish found it advantageous to have their eye sockets higher, and they literally pushed their eyes out so as to have a greater field of vision. The key is that this trait was passed on to future generations. Otherwise the adaptation would have been lost. This is why Darwin staked his entire theory on the ability of organisms to inherit traits acquired through life-struggle by their progenitors. (The reference is in my paper at

    > Mutation is a
    > significant source of the raw genetic variation in a
    > population. We can think of changes being represented
    > as alleles at gene loci. A specific locus can have
    > more than two alleles for a givwn locus, but each
    > individual organism, if diploid, will have only two
    > alleles represented. If homozygous they will have two
    > of the same allele at the locus. Anyway beyond
    > mutation there's also recombination, due to crossing
    > over during meiosis when sex cells are formed. This
    > shuffles alleles in a population with regard to those
    > at other gene loci. When loci are really close on a
    > chromosome they might be considered linked, thus have
    > a higher probability of being carried together. It's
    > this phenomenon of linkage that facilitated mapping of
    > chromosomes in fruitflies during the days of Morgan
    > and his students.
    > Anyway, between mutation and recombination, there's
    > some variation in a population. For a simple scenario,
    > we have two alleles at a locus that determines if a
    > plant is tall or short. Let's say the environment is
    > variable enough at time 0 so that there's no
    > significant advantage to a plant being tall or short.
    > At time 1 a change occurs that favors short plants.
    > The tall plants have a harder time reaching sexual
    > maturity (survival) and passing their tall alleles
    > (reproduction) to the next generation. They tend to
    > not pass their alleles to the next generation. In a
    > sense, this natural process is much like a farmer
    > culling the tall plants in favor of the short plants.
    > The farmer doing it would be artificial selection. The
    > natural process whereby the tall plants are disfavored
    > by the changed environment is natural selection. If
    > the tall plants are totally winnowed over a series of
    > generations, there is a reduction in variation. That's
    > the way directional selection works. It favors one
    > allele (short) at the expense of another (tall) and
    > takes a formerly variable population down a path to
    > reduced variability. Mutation was the original source
    > of the alleles that determined tallness and shortness
    > in the plants. Mutation was the creative spark, so to
    > speak. All selection did was mold the average height
    > of the population until it reached a generally reduced
    > stature. Thus, mutation and selection are separate
    > phenomenon and in this context of directional
    > selection, selection doesn't produce variability, it
    > removes it.
    > If OTOH this population of plants had very small
    > effective size, the allele that is related to tallness
    > could have been lost due to a sampling error over the
    > time of several generations and the short plant allele
    > thus drifted to fixation. This too (genetic drift)
    > reduces variability in the population.
    > In either case, the only instance of tall plants in
    > the population would be if a mutant allele related to
    > tallness were to appear by....MUTATION.

    Exactly. In the reductionistic or mechanistic view, all major changes in anatomy and behavior are traceable to mutations. Sexual recombination merely amplifies changes introduced through genetic mutation.

    > At time 2 the environment might change again to favor
    > tall plants. If the allelic frequencies of the
    > population hadn't shifted (evolution by definition)
    > completely towards small plants via selection and/or
    > drift there might be enough variability for the
    > population of plants to be molded over time where the
    > average height increases as a result of the new
    > seleective regime. And the rare mutation that results
    > in a tall allele will provide a small number of these
    > now important alleles and mutation will facilitate the
    > evolution of the population via selection. But
    > selection didn't provide the variability. It would
    > shift it towards 50%/50% then eventually towards
    > extinction of the short allele.
    > Individual organisms don't adapt, but they can adjust
    > to an environmental change if they hae a wide enough
    > reaction norm or possess enough plasticity in their
    > phenotype.

    In other words, they do adapt. And it's from the intelligent adaptations of individual organisms that we ultimately get the collective adaptations known as evolution.

    > This makes things a little fuzzier than my
    > simplistic tall versus short allele above. If say
    > multiple gene loci are involved in the development of
    > a given trait and if there's enough feedback from the
    > environment where individual plants can adjust their
    > height to an environmental change (like if the
    > environment has had a history of being variable, so
    > plants tend to have the ability to adjust height and
    > have evolved the right response mechanisms to
    > facilitate this change) the environmental change will
    > be buffered a bit and instead of a harsh either or
    > selective regime where tall plants are culled at the
    > expense of short plants, the individual plants go
    > through a process where their height is reduced during
    > their lifetime. But there will possibly be individual
    > variability in the ability to make this adjustment. So
    > some plants will still tend to be favored, those
    > making the best response to the environmental trigger
    > by decreasing their height. If the environment stays
    > the same over multiple generations, the subsequent
    > descendants may slowly lose their ability to make a
    > response towards tallness, thus the reaction norm
    > reduces towards the shorter end of the spectrum and
    > individual plants begin having less plasticity.
    > If above you were hinting at the Baldwin effect, maybe
    > we can shift to an hypothetic situation where behavior
    > can lead the way for evolution via selection. We have
    > a pond of fish (not completely unlike walking catfish)
    > that are able to emerge from the pond when the need
    > arises. Mutation and recombination may have resulted
    > in some variability in this population as far as
    > abilities to live in drier conditions. Let's say these
    > fish eat insects found at the shoreline. Some fish
    > stick to feeding while in the water, but others
    > venture more into the shallows and the drier or muddy
    > areas. Those with a tendency to prefer drier areas may
    > start eating insect species that are more often than
    > not found on land, but sometimes in the water.
    > Individuals (if this genetic variabiility exists) that
    > tend to venture out of the water more will eat more
    > and since eating helps them survive to reproductive
    > maturity they might leave more offspring than those
    > staying more in the deeper water, especially if
    > something adverse happens to the insects that tend to
    > stay at the water surface, versus those on land. The
    > water preferring fish start dying off, but those
    > staying neearer land flourish. In this population
    > there might be some variability for food preferences
    > and for ability to withstand dryness. Over time, the
    > behavioral shifts in preference towards the land
    > insects may result in birth of individual fish that
    > can stay on land and eat more insects to pass their
    > traits to offspring. Over thousands of years the
    > population tends to stay away from the water more.
    > Some individuals may vary in the ability of eggs to
    > withstand dessication. Those that have eggs that can
    > withstand drier conditions will pass these traits to
    > future generations. Another trait with variability is
    > appendage morphology and strength. Those with fleshy
    > fin lobes that have more musculature will pass these
    > traits to subsequent generations. Over time, if the
    > population continues to flourish mutational variation
    > may be randomly injected into the population that
    > results in variation for ability to survive on land
    > (tetrapod limbs, shelled eggs, thicker skin less
    > permeable to water). The water source (ie pond) may
    > shirink or disappear, thus creating a do or die
    > situation for subsequent generations and individual
    > born with variation confering greater ability to live
    > on land will escape the selective grim reaper long
    > enougn to mate and pass their alleles.

    This reminds me of Darwin's speculation that sea mammals originated from the occasional need to get food from streams and lakes. If the members of a given mammalian population continued hunting in water long enough, eventually they might become "so thoroughly aquatic as to brave the open ocean." For Darwin, the main thing was the behavior of mammals in response to environmental conditions, as opposed to "spontaneous variations" in "germ plasm."

    > This had started back when individuals in an ancestral
    > population exhibited a preference for the shore and
    > the prey items located there. This initial behavioral
    > variation resulted in changes in descendant
    > populations beyond behavior itself. Yet muations were
    > at the base. Mutations provided the initial behavioral
    > variability. Mutations also provided the varability in
    > other important traits advantageous to drier
    > environmental conditions. Recombination surely helped
    > too.

    This is an article of faith. Theoretically, it might be a strictly mechanistic process rooted in random genetic mutations, but this is an extremely problematic view of evolution as it removes the main impetus for variation from the creatures whose species actually evolve and places it in chromosomes sealed off in the nuclear compartments of their cells. Instead of animals intelligently deciding to pursue a new path that leads, over the generations, to anatomical changes, it's the occasional transcription error during cell division that provides the raw material on which natural selection operates. It's just kind of a nutty view. Flies in the face of reason. So why is it so widely held?

    The answer is that most biologists, along with educated people generally, subscribe to a metaphysical belief-system known as mechanism. A metaphysical belief is one that attempts to define reality. Mechanism posits that something is real if it operates the way a machine does. According to this view, any belief that posits a mode of operation other than that of machinery is mistaken. However, mechanistic metaphysics does not allow for just any machine to be a model for a natural process but only very primitive machines that work entirely according to the principle of contact mechanics, which states that all causes must be immediate in space and time to their effects. No remote causation. Thus radio doesn't count because radios make use of electromagnetic waves which are known to travel without the need for material mediation. Clearly, this is a primitive belief-system having nothing to do with modern physics or technology.

    A theory of life that allows for action at a distance-- and which doesn't attempt to reduce the whole to its parts-- has several advantages over the crude mechanism of neo-Darwinism. For starters, it allows for the possibility that characteristics acquired through life-struggle can actually be inherited by descendants. Thus adaptations can be transmitted without genetic mediation just as light can travel through deep space without the need for "ether." Secondly, the development of organisms from the egg is a far more viable proposition if the role of genes is only to differentiate individuals within a species rather than providing the overall template common to all members of that species. Third, we know for a fact that the structure of cells, tissues, organs, etc., is holistic. That is, when we describe a cell, we must focus on large-scale structures and patterns of activity rather than molecular activities. While the cell as a whole is ordered, the molecules comprising it are disordered, much as they are in a gas. The order of a cell does not follow from its constituent elements and is therefore holistic. This is precisely the opposite of a machine, which can be defined as any object whose order can be explained entirely due to the nature of its parts and their interactions. Finally, we must confront the experience of actually being alive and conscious. Mind cannot be expressed strictly in terms of brain for the very simple reason that mind entails representation. When we think, we represent items in the world outside of us. The thought of the table represents or points to the table. Yet brains are strictly material, and no set of atoms, no matter how complex, can ever be anything other than itself. Where the principle of mind is A (thought) equals B (table), in the brain the principle is A equals A.

    Only the holistic model of life, including the potential for action at a distance, offers a satisfactory explanation of evolution, development, morphology, and consciousness. Biologists generally prefer the mechanistic model for no other reason than the fact that it accords with their ingrained and unreflective metaphysical assumption.


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