Re: Paper: A critique of directionality theory


"Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx> wrote in message
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Proceedings: Biological Sciences
ISSN: 0962-8452 (Paper) 1471-2954 (Online)
Issue: Volume 273, Number 1586 / March 07, 2006

Pages: 635 - 639
DOI: 10.1098/rspb.2005.3344

A critique of directionality theory

Michael Bulmer A1
A1 The Old Vicarage Chittlehampton, Umberleigh, Devon EX37 9RQ, UK

Abstract:
Directionality theory suggests that demographic entropy, defined in a way
analogous to thermodynamic entropy, is as important as the Malthusian
parameter in determining life history evolution in an age-structured
population. In particular, it suggests that entropy should increase in
equilibrium species and decrease in opportunistic species. This theory has
been applied to explain the evolution of body size and of senescence. It
has
been claimed recently that this theory has been validated by a simulation
study, but it is argued here that this study reveals substantial flaws in
directionality theory and that the Malthusian parameter rather than
entropy
is the appropriate tool in the study of life history evolution.

What is being compared and analyzed in the article?

ECOLOGICAL CONSTRAINTS can be viewed as filters, whereby selection means
nothing more, nor anything less, than: Some prevail, some squeak by, and
some don't get to stick around long enough to reproduce; and those of the
first two are the parents of any and all successors.

LIFE-HISTORY PROPERTIES ??? Hmmmm. Life history, as viewed in respect to
a single organism, begins with its beginning, we might suppose. But, for a
cell division, which is the parent and which the offspring? Has one of them
just begun, while the other existed previously? This is no mere splitting
of hairs, or cells. This is a dilemma which blurs the edge of beginnings
and ends for all single-cell organisms. Perhaps we can just view all
single-cell organisms as having a life history that began with the first
one, and that one has not yet died, although some of its clones have. But
let's try moving up from there to multi-cellular organisms. These may have
gotten their start when the first division was unable to extricate whichever
we wish to regard as clonor and which as clonee. And let us skip over all
the events after that and move still farther upward, if you will allow it,
to so complex a set of aggregated "errors" in the process of cell divisions
as to arrive at, say, current H. sapiens. (I carefully avoid the term
"modern," on grounds that the term keeps getting shifted forward, and what
it applied to historically is not what it applies to at any given "now." Of
course, "current" does, also, but more honestly and transparently so.)

But, with all due somberness and sincerity here, when does a complex
multi-cellular organism's life begin? Is it at conception? That raises a
question of what, exactly, "begins" at conception. We know that
fertilization does not occur out of nothingness. Assuming no new "error"
occurs to the total sequences of DNA of donor of sperm and donor of egg we
get a mixture of the two. But wait, it is not "all" of the DNA of either,
either. Each most likely, by far, ends up a distinct combination of "some"
of each parent's codings and 'junk' that is different from any other
fertilization. So what point would I make in reference to this? I'm just
trying to get at what a life history is, so that I can then try to get at
what might be a property thereof. Forgive me please, as I really am trying.

A life history, since it does not begin out of nowhere and nothing, is a
continuation of something. And that something is a life spiral. Why not a
life cycle? Well, the very core meaning of evolution does not resolve into
repetitions of a cycle of exactly the same identical thing repeating over
and over and over again. Each go-around is, however minutely, a tad
different. It happens at a different locus in time and space... and
consequently in a different constellation of things in a ubiquitously and
perpetually changing universe. And no two events ever are precisely the
same event. But my purpose is not to wax so widely as that, except to say
that, for me at least, it would be hard to imagine a moving and changing
universe in which things all happened in exactly the same time, in exactly
the same place and in exactly the "same identical way." Change and motion
pervade all things we know of, including biological reproductions; and
these, in ways which may be vast or miniscule but must "spiral" along,
rather than merely cycling.
But, in any case, reproductions do not occur separate and apart from a
continuity -- call it a "life cycle" or whatever we will. So, if we are to
pick just one increment in the "spiral" of life, if you will, that cannot be
but an arbitrary point of characterization, and point for purposes of
comparison and analysis which is borne of our human cognitive reliance upon
forced pigeon holes to do much orderly thinking at all.

That having been acknowledged, let us say that a unique life history of a
single current H. sapiens begins with the moment of its fertilization and
ends shortly after the time it ceases to "live," (which requires much
qualification as to what that means, but the end of life is not the end of a
life cycle, as I am about to explain, so that end of an organism's "life
history" is not essential to where I am going with all this.) No, life
spirals, if you will, do NOT go from fertilization to death, as some
vulgarly assume it to do, but from fertilization to fertilization to
fertilization... evolutionarily speaking, at least. And we are talking
about biological evolution here, are we not, so it is only the spiral from
fertilization to fertilization we need concern ourselves with, here. (And
if post-reproductive roles are played in keeping the cycle going -- as, for
example, current H. sapiens grand parents stepping in the salvage a survivor
of, say, a divorce or grave illness in one of their succeeding progeny, that
is but one of many other roles played among EXTERNALITIES generally. And
here I must distinguish, to be quite clear, between "externalities" and
"ecologies" since the two -- while they overlap, are not one and the same.
And, while making such clarifications, I might need to mention, also, that
I used the plural of the term ecology with due care and diligence, in view
of the fact that a current H. sapiens organism (individual) enters and exits
many ecologies, by virtue of being geographically mobile and, also, the
inner ecologies of, say, ear, mouth, lungs, liver, upper digestive tract,
stomach, colon, not only are quite separate and distinct from one another
but, also, are best kept that way lest what is a friendly germ in one of
these might be a fatal
pathogen in another.

That should suffice for wrapping our conceptualizations around what a life
history might mean, in the context of bio-evo. So now perhaps we can go
forth into the category of "life-history PROPERTIES."

Unqualified... this could include, say, life span. But is life span a
directly significant "property" of life cycle (or life spiral)? No, not
directly. It is merely one, among many adjuncts characterizing
externalities -- some of which tend to favor one species while disfavoring
another. In the case of humans, long-lived grandparents seem to be a
favorable element, where they provide some of the nurturing of the infant
and the ill. In the case of individual cells, on the other hand, errors in
cell division, or trauma induced imperfections, are best not left hanging
around where they would take up any of a limited amount of space (a
Malthusian issue). But, then too, there comes a time when current H.
sapiens grandparents might stress the limits of our progeny's capacity for
replenishing Social Security coffers, too. So, well, let us say that
relatively speaking, there comes a time for all things, in all species,
including shifting off this mortal coil, and taking our aggregated frailties
and errors out of the way. In the meantime, evolution (qua CHANGES, which
accumulate to some ramifications in life spiralings, including but not
limited to speciations) goes along, from fertilization to fertilization,
impacted not only by externalities and inner and outer ecologies, but also
by way of the fact that change need not in every case be CAUSED nor
DIRECTED, in order for it to occur.

Beware, all ye enter into bio-evo theory, of post hoc ergo propter hoc. It
is a pitfall baited with easy simplicity and is a tempter toward
intellectual laziness at ALL levels of education and pedantry. None is
exempt but by virtue of rigorous and continuous self-examination and
self-discipline.

Having eliminated life span, I think, as a "life-history property," then,
let me examine what else it might mean. Would it be after the fact (as all
history is) what ones phenotype has been? Hmmmm. If one is in a war zone
and steps on a land mine, and his legs are blown off below the knees, is
footlessness, for that individual a "life-history property?"

Sorry. I just find myself unable to come up with what is the meaning of
"life-history property." Perhaps the author of the article in question used
this term to mean "acquired characteristics." Unfortunately, he leaves us
(or me, at least) hanging as to he might mean insofar as to say that
"life-history properties" relate to ecological constraints and give rise to
a central problem in the understanding of each, or both.
From that nebulous island of confusion, he continues on to "directionality
theory."

DIRECTIONALITY THEORY must mean that evolution is theorized to have had,
at each and every juncture, a single direction it was headed ... a
destination perhaps... a predestination perhaps. Of course it has taken
many diverse "directions," as abundantly is in evidence over the course of
"life history" or "life histories in the aggregate," but evidently the
author intends to speak to the net effect of it all -- to the
interstitial incremental mode of all things as they are now. Note that I
avoid the term "end result," and do so for the simple reason that evolution
has not ended yet, and now is -- so far as I can imagine, at least --
still underway and, as at least one theorist has surmised, H. sapiens (or H.
heidelbergensis) or whomever we are may realistically be viewed as a
predecessor, only, of some other H. At least, if we would consider history,
it is not an unprecedented eventuality.

But directionality theory... hmmmmm. I cannot help but wonder what kind of
directionality theory we might attribute to the paths that have been made by
the dipping of earthworms into oil paint, and the dropping of them onto a
canvass.

Perhaps the author can shed some light on that by where he takes the notion
of "directionality" by tossing it up against a wall and studying the
intellectual splatter. The concept of physical entropy is not so simple and
direct as some imagine. It can loosely be defined as a veritable "law"
whereby the energy fed into any system is not ALL available to that system.
(I will not burden you with my view that the very notion of what a system
SHOULD do is nothing more than an anthropocentrically derived normative, and
that all systems, by virtue of having to perform as a part of the universe
as an entirety -- as well as a quasi-separate sub-system of it, cannot
perform with total and absolute independence, but must share energy with the
entirety.) But, in a more narrow sense, entropy is what happens, for
example, when an electric current is fed into a wire and encounters some
"resistance" and some of the energy that is required to produce that energy
does not get expressed as current power, but some of it dissipates into heat
and/or light and... now magnetism is a whole 'nother can of worms... But
suffice it to say that engineers, electrical or otherwise, have been unable
to come up with perpetual motion because the energy out (in form of what we
anthropocentrists would like for it to do to suit us, but some of it does
something else than we would prefer. Physicists agree that mass and energy
may cross over from being one to being the other, but their total "value" is
conserved in the universe. (That is the theory of it, at least, as we have
not measured all the mass and energy in the entire universe just yet. But
all "local" experimentation seems to be reducible to something of the nature
of an "accounting" system -- perhaps even a "cost" accounting system.)

It does seem feasible to suggest that IF there is any predestination for
bio-evolution (as best we know it to be) whereby it has arrived a brick or
two short of the load to which we might theorize it has been trying to go,
but has not quite gotten there, THEN we might very well imagine that there
has been some
diversion of some of the energy put into trying to get it where it otherwise
should have arrived at this
interstitial increment in anthropocentric philosophically conceived
nomativity. It should not surprise anyone if I say that if we do not know,
for a certainty, where evolution is supposed to have gone, it is no easy
matter for us to calculate by just what percentage that is has missed the
mark. But let me not be hasty. The article's author has more to offer us,
in the form of an example, to wit: "a measure of the uncertainty in the age
of the mother of a randomly chosen newborn, provides an analytical framework
for addressing this problem."

Indeed? Hmmmm. He goes on to say:

" The theory predicts that in populations that spend the greater part of
their evolutionary history in the stationary growth phase (equilibrium
species), entropy will increase. Equilibrium species will be characterized
by high iteroparity and strong demographic stability. In populations that
spend the greater part of their evolutionary history in the exponential
growth phase (opportunistic species), entropy will decrease when population
size is large, and will undergo random variation when population size is
small."

Why does this remind me of something I read once in a book titled, Outline
of Abnormal Psychology?
It was about a psychiatric patient who developed a paranoid pseudo-community
which was plotting to destroy him, based upon something to do with the
numbers in the date of his birth, the name of the street the lived on, the
color of hydrangeas... or some such concatenational conglomerate which only
he, the patient, was able to see the connections between. (The particulars
I made up, here, but the nature of the patient's reasoning I did not.)

What I am trying to say is that it takes no genius, I do not think, to
reason that species at different times and places encounter different
opportunity sets which -- provided they have evolved up to then some
capacity for availing themselves of same -- they will avail themselves of
same and not die off, or not so much so as other species which up to that
time have not cumulated that as much of, or so many of, traits enabling
availance of the particular set of opportunities (and hazards) comprising
the externality conglomerate. And, I would be remiss not to mention that it
is only those who stick around and donate sperm or egg, and who then stick
around -- where and as necessary -- and get the infants up and running
before kicking the bucket -- who get to have any role in passing on
anything.

So, pardon my lack of gullibility if I ask what entropy has to do with that.

Though I hate to repeat myself, what direction were the species SUPPOSED to
take? And who or what, exactly, are we to presume DETERMINED the direction
what was equilibrium, as opposed to disequilibrium, in the context of what
was a homeostatic sub-system, and NOT a system designed to go in only one
direction.

Understand, please, that I am not saying offspring do not resemble their
parents. The fact that they do tend to do so is abundantly in evidence.
But the fact that "errors" or "change," if you will DO occur from
fertilization to fertilization ALSO is in evidence. So, unless there is
assumed that there is a single, unswerving direction... a precisely
duplicative life cycling, as opposed to a "spiraling" then the only thing
NOT changing is change, itself.

Granted: My view that the very notion that any sub-system in the universe
is unable to exist and perform unto itself, with being in a loose sense
"taxed" by the universe to support the interconnectivity of the entirety of
the universal system as a whole, does (I would maintain) support and uphold
the fact that no two fertilizations/reproductions are identical, from the
outset. In fact, the universe as an entirety is NOT
in stasis but in HOMEOSTASIS, and matter and energy -- while they may be
conserved as a whole, do not simply remain in a steady state, heading all in
parallel, all on a single, and hence, predestined vector which is not
impacted by any internal variegation.

Of course a population changes in a relatively stable externality
conglomerate. (Even stable ecologies are not static, for crying out loud.)
I am objecting to is the insinuation that such change is a departure from a
single vector of change which exists only as a construct of the human
imagination in plotting some points along a line and saying, "Ah ha ! Here
it deviated from where it would have gone, but for entropy."

Let's continue on with the author's words:

"Opportunistic species will be characterized by weak iteroparity and weak
demographic stability when population size is large, and random variations
in these attributes when population size is small."

Since when would the author have us think that members of a species, being
in a particular place at a particular time, and having accumulated --
through spiralar changes in their morphology over a series of
fertilizations/reproductions an assortment of capabilities would not be
opportunistic -- NOT avail. Or, conversely, how would a species which,
being in a particular place at a particular time, and having NOT
accumulated -- through spiralar changes in their morphology over a series of
fertilizations/reproductions a set of capacities for availing themselves of
some opportunity AVAIL themselves of same, regardless.
The point is, opportunity is as opportunity is. What is an opportunity for
a ruminant is NOT an opportunity for a non-ruminant. Cows do not choose to
nourish themselves by sucking blood of other mammals, nor do
sanguinary-dieted bats choose to eat grass. iteoparity or no iteoparity.

While it does stand to reason that the more individuals there are in an
interreproducible population the greater the chance for "errors" or "newly
composed sequence variations" to occur (the latter referring, for example,
to, say, random alu insertions which -- though it be statistically
unlikely -- can get around to producing a "genetically significant" new
sequence variant that would avail a present or future opportunity
relationship with something in the environment. It also stands to reason
that change would occur in a relatively stable ecological setting. It ALSO
stands to reason that -- millions of years thereafter -- what a
paleontologist might find most interesting might be what occurs when a new
CHALLENGE occurred by way of some remarkable change FOLLOWING origination
and accumulation of a genetically evolved capacity to avail, or a
genetically evolved incapacity to avail of the NEWER externality
conglomerate. The newer externality change might be anything from a
relatively sudden arrival of a pathogen on the scene, a relatively sudden
arrival of a new food supplying plant... or, on the negative side, an
arrival of a new predator species that has migrated in, or become driven out
of another area by drought there...

The variations in the dynamic between changes in form of new opportunities
(favorable) and new adversarials (unfavorable) on the one hand and, ON THE
OTHER HAND, new opportunity availance capacities (favorable) and lack
thereof (unfavorable) would change the homeostatic dynamic as a mega-system
in ways that -- evolutionary theorists, centuries, millennia, or eons later
might be tempted to interpret only on basis of what APPEAR to be a result of
quick versus slow genetic swings but which might actually be mega-results of
sudden changes in the dynamic which filter out some genetic changes that had
been accumulating gradually over a very long period of prior time, and which
enables a species, or those individuals WITHIN a species, which have certain
availance capacities to be the only ones to pass along anything.

And, in terms of evolutionary time, it is not inconceivable that a species
almost wiped out, and leaving behind only, say, ten percent of their number,
might appear (as historically measured) to have EXPLODED in population,
WITHOUT having been almost wiped out, because the fossil record does not
tick off the seconds and minutes, nor sometimes even centuries... but longer
units of measurement. And genetic variations, which could have been spread
not only singly but where PAIRED with immediately opportunity-availance
capacities, might serve better at after a sudden CHANGE in
opportunity/adversity to promote survival of those individuals inheriting
it. This is not far fetched. Those who are studying the decline in
usefulness in antibiotics are seeing examples of it in the here and now...
today. And the decline in them COULD, at a time in the future of current H.
sapiens, IMMEASURABLE in evolutionary or geological seconds and minutes as
it were, take on a semblance in fossils of a million years hence, the
appearance of a sudden failure of H. sapiens genes to sustain a population
level, from a Malthusian point of view, that will have had NOTHING to do
with food supply versus population size.

Now on to the conclusion (or conclusion of the critique) and:

"This paper assesses the validity of these predictions by employing a
demographic dataset of 66 species of perennial plants. This empirical
analysis is consistent with directionality theory and provides support for
its significance as an explanatory and predictive model of life-history
evolution."

Sorry, I am unconvinced that there is any tangible meaning of
"directionality" in this context, nor any way to measure any quantitative
entropic margin of deviation therefrom. I do not see that it adds anything
to explaining anything other than the basic homeostasis and spiralar change
over many reproductions, and the interactions of these changes -- favoring
some here, disfavoring others there. Nor do I perceive life history to be
anything more than hindsight.

g





.

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