From: ingles@engin.umich.edu (Ray Ingles)
Subject: Re: Clarification on Microevolution and Macroevolution
Date: Wed, 14 Oct 92 14:00:29 EDT
Organization: University of Michigan Engineering, Ann Arbor

In article <1992Oct14.084309.12171@hsr.no> onar@hsr.no (Onar Aam) writes:
>
>
>Thankyou, Ray, for intelligent remarks.

 Well, it's nice of you to say so, but I think that we'd really benefit
from a real biologist or two hopping in... :->

>> 2) However, there is a major factor you're overlooking here- multicellularity

 [deletions]

>If you read my text more carefully you will see that I stated that
>multicellular life did not have the same selective preassure on efficiency as do
>bacterias. This is effect the same thing you are saying.

 Point (somewhat) conceded. I still think you are overlooking the degree
to which this affects things, but I can't really make a case for it so
I won't post a lot of ignorant speculation.
 (I just realized that could be interpreted as a sideways insult to you.
That's not what I meant; I just don't feel qualified to argue this point.)

>> 3) Indeed, it's even more complicated because there's so much junk DNA in
>>modern creatures. This drastically increases the 'dynamic range' you propose,
>>since we need not add genes to an existing species to expand the number of
>>active genes- just activate some junk. (Of course, it would be rare that such
>>an activation was beneficial, but beneficial point mutations are rare too.)
>
>Junk DNA is largely a biproduct of evolution. Much of it is pseudogenes, eroded
>genes left over after a geneduplication.

 But this just means that it is even more potentially functional than any
random peice of DNA. I still think this affects the 'dynamic range' you're
talking about drastically. I.e. there's a lot more DNA than is being used
at any given time; thus, new functions can be added simply by (fortuitously)
accessing junk DNA (or dropping some function into the 'junk') rather than
adding new genes _de_novo_. (I always wanted to use that phrase...:-> )

>> 4) Gene increase happens all the time. I understand ome species of mosquito
>>gained a near-immunity to a common pesticide by doubling the gene that codes
>>for a protein that meabolizes the pesticide-- and this happened in recent
>>times. Given a few billion years, genome expansion is not all that unlikely.
>>(Does anyone have a reference for this?)
>
>This is exactly what I am saying. Although I never said that geneduplication HAS
>to have great impact on the species. In most cases it does not. (Hence all the
>junk DNA)

 I'm trying to understand your point, then. Are you saying that the role
of gene duplication (or other forms of genome expansion) is not fully
appreciated in modern evolutionary theory, or what?

>>> But what I CAN do is to sketch the 'typical' path of evolution:
>>>
>>>Assume that you have a specie which is adapted to the environment in
>>>which it lives. It can then be said to be in a state of genetic stability.
>>>The species remains approximately unchanged for a large amount of time,
>>>say 10 million years. Suddenly there occurs a new gene in the genome which
>>>alters the specie sufficiently to be called a new specie. The new specie
>>>is probably in the state of genetic unstability.
>>>Therefore the selective preassure on the new specie will
>>>be strong and will therefore undergo a time of rapid microevolution until
>>>genetic stability once again is reached.
>>
>> This is almost exactly opposite to the way evolution is proposed to act.
>>Or is that your point? I mean, the general idea of evolution is that
>>if the *environment* changes the species alters to fit the new environment.
>>This has been recently extended to note that small, geographically isolated
>>populations are much more sensitive to environmntal pressure and much more
>>likely to speciate under such conditions.
>>(Again, I'm no biologist, and I'd appreciate someone summarizing that better.)
>
>
>Again, what you say is absolutely true. I never stated WHY it happened, I merely
>stated HOW it happened. Thus, my statement does not contradict yours, does it?

 So you are saying that current evolutionary theory has the cause and effect
reversed?
 What current evolutionary theory says (as far as I understand it) is that
mutations, gene duplications, etc. happen at a fairly constant rate. (Except
maybe in some bacteria.) If a population is both small, and isolated from
other groups of the same species, then a given mutation, if beneficial,
has a much greater chance of spreading throughout the population.
 Given a bit more time, and a few sets of mutations occurring, the isolated
subgroup may become unable to breed with the wider population; i.e. a new
species emerges. If the geographical isolation is later removed (an earthquake
opens up a previously isolated valley, etc.) the two species, old and new,
will intermingle. If the new species still competes with the old species,
and is better at competing, it will tend to drive out the old species.
 What you seem to be proposing is that a new species will emerge if the
new mutation is such that it 'destabilizes' the previous equilibrium. In
the section I originally responded to, you seem to be saying that a species
which is already adapted to its environment still has selection pressure
to make major changes or something... What in the above characterization I
gave do you disagree with, or would like to add to?

>> No, no, no. you seem to think that species undergo massive changes in short
>>periods of time. This is not supported in the fossil record. A new species
>>usually looks almost exactly like an old species. Not only that, they generally
>>have almost the same lifestyle as its 'parent' species- slight differences,
>>at most.
>> If the changes in environment are too great... the species goes extinct without
>>the chance to give rise to a new species that can handle it.

 [Sabretooth example deleted]

>The fossil record supports long spans with no (read small) change and then
>sudden change. It is called Punctuated Equilibrium. (the change need not be great)

 'Sudden' on what scale? The timescale of the kind of mutation you seem to
be proposing is effectively instantaneous; speciation usually takes at *least*
a few hundred years (generally) I understand.

[deletions]

>You are right again. I mentioned that to show that small changes (like a mutation)
>could produce immense effects. An interesting thing to philosophise about is
>whether chimps and humans can produce firtile offsprings. (Not under natural
>conditions, that is. Some parts of the genomes need to be fixed a bit.) And the
>scaring thing is that they probably could...

 I have heard that some genetics researchers have successfully combined
human and hamster genetic material;  the resulting embryos develop for
quite awhile before dying. (I have no references for this, though... should
I hop over to alt.folklore.science with this one?) It's an interesting
question as to whether these 'humsters' could ever make it to term... but
I doubt it.

>> Hey, I'm a chaos enthusiast too, Onar. (I also recommend that people at
>>least read Chaos, it's an awesome book!) But let's not get carried away.
>>We can't really know how chaos theory applies to evolution yet.
>> For example, how could we plot a strange attractor for evolution? How
>>many dimensions do you think it would have? What variables, and what would
>>be the Lyapunov exponents? Can we give a rigorous definition that would allow
>>us to state, "This species is more complex thant that one"? What routes to
>>chaos do you think apply... bifurcation? Period doubling? What would be
>>the initial critical points?
>
>
>Ray, I am sure that you know that biological clocks are governed by chaotic
>mechanisms. Some of these have already been well mapped. That evolution is also
>governed by chaotic mechanisms is also fairly well detected - and for the same
>reasons.

 We know biological clocks (like heartbeat, etc.) are governed by nonlinear
systems that can be pushed into chaotic regimes, yes. And many biological
structures can be successfully modeled as fractals (like lungs, blood vessels,
etc.) But that is because we can do the calculations and measure the effects.
 I would *really* like to see how this effect has been detected in 'evolution'
(hopefully in some journal article?).

> Biological systems (cells,organs,organisms etc.) are all
>"far-from-equilibrium" systems; they need a constant flow of energy to retain the
>potential that drives them. Take away the energy (food) and they die. An analogy
>can be produced for evolution. Life as a whole is ultimately a
>"far-from-equilibrium" system with its main energy source from the sun. The
>energy is expressed in form of natural selection.

 Um, actually, I think the energy is expressed in metabolizing and
reproducing. Natural selection is at least a second-order effect.

>                                                   If a gene is subject to
>selective preassure then it will be preserved (potential retained). If not then
>the gene will erode (die). This system is clearly a nonlinear process. And you
                                                     ^^^^^^^^^ ^^^^^^^
Not all that is nonlinear is chaotic/fractal, even though all that is
fractal/chaotic is nonlinear.

>yourself stated the problems: we don't have a clue to how evolution "really"
>works. That is perhaps some of the greatest tasks in biology in the future. Heavy
>research is needed. And therefore I don't have the capasity to answer your
>questions.

 okay, so this is just your best guess/speculation, right? You're saying you
*suspect* this but can't prove it yet, I take it?
 (That's not an attack, I'm trying to make sure I understand what you
say.)

>Onar.


Sincerely,

Ray Ingles                  || The above opinions are probably
                            || not those of the University of
ingles@engin.umich.edu      || Michigan. Yet.