The Perpetual Motion of Evolution:

Discussion in 'Biology & Genetics' started by paddoboy, Nov 8, 2016.

  1. DaveC426913 Valued Senior Member

    I'm afraid I'm with Michael on this. That tree of life is an artifact of the visualization technique. It is only fractal in superficial ways. eg.

    • Major branches are few, long and thick, whereas minor branches are many, short and thin. But those have no relevance - no counterpart - in the actual mechanic of evolution. They are an arbitrary human projection onto the diagram.
    • If length of branch is mappable to time (what is length representing??), then there is no reason that some of the "narrowest twigs" in that diagram shouldn't be extremely twigs, whole others might be mere stubs. The appearance of thick=long and thin=short is, as above, an arbitrary human projection onto the diagram.
    The self-similarity, a hallmark of fractal processes, is imposed upon the visualization. IOW, we're making it look fractal, because it suits our aesthetics, not because the mechanics of evolutionary speciation actually dictate fractal growth.
    Last edited: Jan 29, 2017
    Michael 345 and exchemist like this.
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  3. Michael 345 Valued Senior Member

    You put it so much better thanks
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  5. Yazata Valued Senior Member

    It's a graphical representation of phylogenetic relationships.

    It certainly seems to show a large degree of self-similarity at different scales.

    That's probably true of the image in the Onezoom link. But I don't think that the fractal nature of the tree at the bottom of this page depends on the thickness and length of the branches. It's more a matter of how the branches divide and subdivide into new branches at all scales.

    I don't see why they need to. The tree at the bottom of this post is just depicting which taxonomic groups are believed to have common ancestries.

    But if we want thickness to be meaningful, then thickness could be used as an indicator of how prolific the branch is, of how many subsequent divisions there are down-stream. In that kind of tree, Insecta would be a very thick branch, while some of the more obscure invertebrates like tube-worms where only a handful of species exist would be a lot thinner. Or it could be an indicator of the taxonomic category they represent (with kingdom and phyla thicker than class, order and genera, for example). It's a matter of choice, I guess, but the choice doesn't make it stop looking like a fractal.

    In the tree in the bottom of this post it seems to represent distance from last common ancestor. I suppose that's a matter of time, certainly amount of accumulated change. The far branches are further removed from LUCA (last universal common ancestor, the original cells) than the branches at the lower bottom between Bacteria and Archaea (where LUCA presumably lies).

    One could construct a tree where short branches that divide rapidly represent evolutionary lineages that subdivided rapidly, while long outward lines without many branches might indicate taxa that survived for a long time without any big changes. (Presumably organisms very well adapted to their ecology. Some insects today closely resemble insects from many millions of years ago, trapped in amber.) I think that everyone acknowledges that evolutionary change doesn't always proceed at one fixed speed and a tree could be drawn so as to depict that.

    I thoroughly agree with that criticism of the Onezoom image in my earlier post, but I don't think that it applies so well to the one below or that it has very much to do with the fractal appearance of the phylogenetic tree.

    I'm inclined to think of biological evolution as a process of successive elaborations on elaborations on elaborations. Which results in in an ever increasing number of variants in countless branching lineages. And that results in an evolutionary history of life that I believe resembles a fractal.

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    Last edited: Jan 29, 2017
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  7. DaveC426913 Valued Senior Member

    We know what it is.

    Please Register or Log in to view the hidden image!

    I'm saying the representation is made of design components that have no counterpart in actual evolution. So, the diagram merely looks self-similar - for design and clarity purposes.

    Again, note how all the individual species branches seem to be the same length - as if they are self-similar.
    But is that representative of reality?

    Does evolution produce a similar number of species from a wide set of parent branches?
    Did evolution produce as many ant species and mammal as beetle species?
    species of a given class live and go extinct after a similar passage of time? (i,e, do all canary species live the same 30 generations before speciating or going extinct?)

    Obviously, those is are not hard arguments I'm making - they're hypotheticals. What I'm asking is: does the diagram's apparently self-similar elements represent real relationships in the evolutionary mechanism? Or are they imposed?

    The map is not the territory.

    I argue that that is imposed, not emergent.

    You know the expression "God had an inordinate fondness for beetles."?

    It would be revealing to see if the beetle population is as exhaustively represented as is the marsupial population.
    Or the bacteria or fungi.

    I say that this diagram is highly suspect of representing the mechanisms of evolution, in ways of which I've only scratched the surface. And therefore a very weak argument.
  8. Michael 345 Valued Senior Member

    This looks more like the tree of life I am used to

    The other looks more like a drunk spider's web

    However if you accept the view of life which states all the diversity of life comes from a single organisim the diagram is so wrong

    Surely the 'trunk' would be a thin whisp and growing in thickness as it travels upwards

    While branches try to show species all life is linked by DNA

    May be the tree should just look like a line growing in thickness

    Since all life is equal at its current stage of evolution the end of the thick line would be flat and continue to remain flat as evolution continues

    No organisim can jump ahead of others in its time line of evolution

    Diverge due to environment yes but would remain alongside similar

    But i guess a single line of increasing thickness is not as pleasing as a tree

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  9. Write4U Valued Senior Member

    You are correct, the fractal function is imposed because there is no other way to graph (simulate) the relationships between species. Fractality is a universal mathematical imperative. Is this not why we use the term "evolutionary tree" or "family tree" and the term "branching"?

    A single seed beginning to sprout by a fractal function because the genetic code orders the simplest growth form, which is by the fractal (self-similarity) function. It is the fractal function itself which provides the emergence of the enormous variety of fractal structures.
    Last edited: Jan 29, 2017
  10. Write4U Valued Senior Member

    Ok , you asked why we have thicker and thinner branches. Let me try an analogy.

    Visualize,, the *trunk* is the "common ancestor", which somewhere splits into branches (evolving into the next generation) of younger species, and so forth, until we come to the leaves and flowers representing the most recent extant species.
  11. Yazata Valued Senior Member

    Apparently branches on phylogenetic trees sometimes do have a thickness dimension. This has to do with the fact that they aren't just phylogenetic lineages in an abstract taxonomic sense, they can also be interpreted as populations in a population biology sense, hence as a whole collection of individuals and their lineages in the parents-offspring sense. So the thickness of the branch can sometimes be used to represent the genetic diversity and heterogeneity within the population.
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