Re: NS and AaD curves


"g" <gillawton@xxxxxxxxxxxxx> wrote in message news:...
>
(SNIP)

(Note: The point at issue here is the concept implied by "fitness" (as
applied in the phrase "survival of the fittest").

>> ... I think it's a problem with the way the
>> subject is presented. The way out of the circular definition is to
>> notice that we can define fitness in terms of other properties of an
>> organism. For example, if we introduce a crop variety with a new
>> disease resistance to farmers, then we can predict that a fungus which
>> does not have the protein that is used by the resistance to detect the
>> fungus will survive better, and hence be fitter (and all that that
>> entails). In other words, we can go from a physiological, biochemical
>> or anatomical measurement to a prediction in change in frequency.
>> Fitness is just the bridging concept that helps us do it.
>>
Bob,

This explanation strikes me as being not wrong, in the example tendered,
limited to many valid categorical, or anecdotal, examples. My issue with
the concept is that the expression "survival of the fittest" and the word
"fitness" not only are used to explain equally valid categorical
applications and anecdotal experimental results, but then are used
frequently to "explain" blanketly something that has occurred in biological
evolution, thus surfing over many categorical and anecdotal EXCEPTIONS.

One genetically transmissible characteristic in a species of fish, say the
specialized fins and bodily size and form of a flying fish species, enables
it to escape predators by leaping out of the water and sailing for a
distance. Not a problem, so far as it goes. Those that can leap the
highest and sail the farthest may "make the cut" and get to live to breed
another day. Those less agile and aerodynamic, do not make the cut. In
another fish species, however, another genetically transmissible
characteristic, antithetical to being able to leave the water's surface and
sail -- largeness, say -- enables it to fend off many of its would-be
predators. In this case, the larger and heavier and -- even if by
coincidence only -- the LESS equipt a member of the species would be to leap
out of the water and sail a great distance, renders it fittest of its
category. In a desert terrapin, another genetically transmissible
characteristic, say a specialized kind of skin that does not give up
moisture too readily -- enables it to get by on less water than is required
by either of the kinds of fish forementioned. For a giraffe, length of the
neck might make it fittest. For a gazelle, a long neck might assure a very
short life. And so on, and so on, and so on through a veritable
astronomical number of diverse specializations which, in another species,
could mean instant death.

Maybe there are a few genes that provide characteristics that would render a
benefit anywhere, anytime, in any species, under any conditions. For all I
know the creatures that respire sulphur dioxide may have some genes in
common with oxygen respiring organisms. Not having a list in front of me of
all the genes in all the flora and fauna of earth in one column of a spread
***, and the characteristics it codes for in a parallel column (or SEVERAL
parallel columns, if different expressions are associated with that gene) I
cannot venture a guess as to how many of those there are. I can only guess
that the genes that are conserved (assuming they do, in fact, yield more
generally advantageous characteristics across many species lines) are in the
minority.

Another problem that fuzzies the meaning of 'fitness' is that "sheets
happen. (:>) For example, if a human has chosen the best of all possible
great grand parents from the best of gene pools and at the best of all times
and places in the best of all parallel universes and gets run over by the
worst of all Mac trucks, he's a goner. And, as if that were not enough, if
a comet of the size alleged by some to have made the world unready to
continue
supporting dinosaurs were to strike the earth today, and ten million people
got vaporized instantly by it, they would not be selected on basis of their
genes, and concommitant 'fitness' characteristics any more than the
dinosaurs were. So, is that not an exception to the "survival of the
fittest" hypothesis? Or, if a pandemic were to sweep the world and kill off
a billion people whose immune systems had never had an opportunity to
prepare any antibodies to it, perhaps some percentage of them might have
some gene or combination of genes that would exempt them. Let's say that
some psychoneurotic guy lives in cave in a swamp, because of some genetic
coding that renders him anti-social, and he does not get infected. Let's
suppose that, after the pandemic has passed, and our swamp hermit has a
sufficient libido to venture out of the swamp and rape a few of the
pandemic-surviving females, and a few children result, and a few inherit the
gene or genes that assured
survival in his anecdotal case. That gene, or those genes, survived.
Right? Survival of the fittest. Right?
Allllll righteee then. We've just found ourselves a dad burned fitness
gene.

All kidding aside, it is a given that truth sometimes is stranger than any
fiction we humans might make up, so the fictional scenario could happen.

Nothing I have said here is impossible, and some of it is routine.

Oh, I almost forgot... animal husbandry and human agricultural management.
Hmmmmm. Let's see now...

In animal husbandry, and in agriculture, we humans can intercede into, and
control, TO SOME EXTENT, certain characteristics, even without knowing
necessarily what gene or combinations of genes give rise to what WE select
for, to maximize characteristics we want. Where we do this, we select the
plants and animals that tend to be nearer to what we want in the end --
large, beefy bovine, slender big-bagged milk cow, plants the produce more
fructus to the acre, with the least moisture... no... wait... sometimes we
choose plants that like lots of moisture for areas that have lots of it.
Okay, not a problem. In general we pick a characteristic we would like to
end up with, and up with plants and animals that are "narrowly specialized."
What we do NOT do (to my knowledge) is INCLUDE in our goal any selection for
being able to survive outside the confines of our "human selection" process.
What we end up with has tended, in the past at least, to be bred without
regard to characteristics that work well outside our arena of control. In
fact, sometimes the last thing we would want is for an agricultural plant or
animal to be able to cope well without us. Some of us say that we have
"interfered" with "natural selection," by performing "human selection."
However, when we think about that, we have not so much interfered with any
selection process as steered specialization. In the wild (or, in nature,
the plants that are able to scrape by, and those that become post-endangered
(as in gone) and those that prevail in one time at one place under one set
of conditions, gives way to change over time, such that today's master
fitter in becomes tomorrows bye bye loser has-been. Times and conditions
change and survival characteristics change with it. But that doesn't just
apply in nature. Hey, if we buy a school bus, drive it to the back forty,
remove the wheels from it, fill it with all the scrap iron and other junk to
avoid tearing up the blade on the bush hog, that is a "human-steered
specialization" One specialization of form and function, more often than
not, is adverse to another, and in this case, if we decide to use that bus
to haul kids to school, it probably ain't goin' to be 'fit' (in Arkansas
they say it ain't 'fitten' fer that no more).

I could probably find a more impressive way to explain and exemplify this,
but the point would be the same. Nature is not a seamless, internally and
externally consistent, single set of relationships, that remain the same.
Of all nature's characteristics the only sense it stays the same -- over
evolutionary and geological spans of time, at least -- is by continuing to
change. Fitness only describes what still remains after one cloud of smoke
clears. After the next one clears what remains is not the same identical
things that were there after the first cloud dispersed.

If someone wants to look at what is left after the smoke clears and call it
"the fittest," just to put that in a box, and lable it, that makes sense.
We can throw socks and underwear and kids toys and a ball of twine in a box,
too. And we can call the contents of the box, the stuff that was "fittest."

But we could also call it, the things that did not get destroyed or thrown
away the last time we cleaned house.

Let me say, once again, with head bloody and unbowed: The concept of
"survival of the fittest" can be equally accurately described, it seems
clear to me as, "survival of the survivor, as of a given place and time and
set of conditions. Beyond that, lies change... change brought about by
genetic drift (the mechanics of which are well documented in genetic
research).

Meet me back here a hundred million years from today and, if the creatures
we deem to be "fittest" today are still around in exactly the same "fit"
form, and functioning in exactly the same way as now, then I will concede
that they shall have proved the "fittest" after all.

In the meantime, if you want to explain why something has evolved, and you
simply say, "Oh, it's because it was the "fittest," I'm too unintelligent to
understand how that translates into any clear and unambiguous meaning, much
less one that would inform any empirically testable hypotheses.

g

>>>
>>>>Where you are right is in seeing that there is not fitness "plan":
>>>>anmals don't go around with their fitness stamped on their heads (*).
>>>
>>>
>>> Never mind the bonus points, but the analogy of something that would
>>> indicate a link between outward appearance and predisposition to survive
>>> does not ring relevant for me, especially in consideration of the fact I
>>> did
>>> not intend any such link.
>>>
>>>
>>>>Instead they reproduce and die at varying rates.
>>>
>>>
>>> Yes, but one of the issues I have in trying to grasp this is that there
>>> is
>>> no gene that works in all sets of externalities. For example, a gene
>>> (or
>>> alternative gene splicing) that renders the legs of a snake so
>>> unremarkable
>>> in expression as to be invisible and, hence, disabuses the snake of
>>> expending energy to grow them and then drag them around all its life,
>>> does
>>> NOT benefit, say, a horse.
>>>
>>> For all I know, the very same gene that may trigger vastly different
>>> expressions of a 'hand' in a whale, versus a hand in a bonobo, versus a
>>> hand
>>> of a human... has been conserved over what... thousands of years...?
>>> millions...? billions...?
>>
>> (I'm not quite sure what you're getting at, so I'll try and cover both
>> bases)
>>
>> That's possible, but of course there will be a gene somewhere that is
>> dfferent.
>>
>> Of course, many genes will be expressed in response to a change in the
>> environment. A classic example is the lac operon, which codes for
>> lactose digestion in bacteria, and is switched on and off by the
>> presence/absence of lactose. So you may see the same genotypes have
>> very different phenotypes, depending on the environment. This is called
>> "phenotypic plasticity".
>>
>> (Again, let me emphasize that the new-to-me
>>> comprehension of the fact that alternative gene splicings can be found,
>>> which utilize alus to derive any of two or more alternative protiens,
>>> and
>>> thus provide a logical mechanism for conceiving of variant 'responses'
>>> for
>>> variant local externalities, removes the gut feeling I so long
>>> experienced
>>> that "something was missing" from the evolution via genes, only
>>> miscognation. And, hopefully, out of that, or out of some similar
>>> expansion
>>> of possibilities, might come a eureka experience out of my dilemma over
>>> 'survival of the fittest.')
>>>
>>>
>>>>that mean that they reproduce more, or die at a lower rate, will tends
>>>>to pass on their genes: hence evolution.
>>>
>>>
>>> Sorry. With all due respect, that is too broad and vague to enable me
>>> to
>>> remove my gaps in understanding it.
>>>
>>>
>>>>We use fitness to quantify
>>>>this, i.e. to put a number on the differential rate at which genes are
>>>>passed on.
>>>
>>>
>>> Again, with utmost respect, and with utmost desire to 'get it,' there
>>> are
>>> too many conserved genes, shared in common by far too many grossly
>>> different
>>> (in form and function) species, for me to see how the passing on of a
>>> given
>>> gene produces a specific 'adaptive' result every time.
>>>
>> I don't see the problem (well, apaer from our mutual inability to
>> understand where the other one is coming from!). If geens are conserved
>> between species, then they are probably conserved within a species. So,
>> they are not evolving. It's the genes that are not conserved, i.e. that
>> vary within a species, that can evolve. The fact that they do it in a
>> genetic background that is constant doesn't make much difference. There
>> are still enough genes varying to allow adaptive evolution.

This seems accurate to me. What it does not do for me is define "fitness,"
which is the concept I still cannot see as precise enough in meaning to
grasp, other than on basis of a category box to describe an
ever mutating set of survivors, the characteristics of which do not float to
the top of the survival list
consistently, but which are the ones who got the luck of the genetic draw at
the particular time, place, circumstances in which they happened to come
along.

ENORMOUS respect for you, and for all who would hope to rescue me from my
unintelligent groping for the meaning of some of the words offered as the
"magic bullets" which are designed to dispell such ignorance as mine, but
have not yet found their mark, in my case.

g

>> Bob
>
>>

>> Bob O'Hara
>> Department of Mathematics and Statistics
>> P.O. Box 68 (Gustaf Hällströmin katu 2b)
>> FIN-00014 University of Helsinki
>> Finland
>>
>> Telephone: +358-9-191 51479
>> Mobile: +358 50 599 0540
>> Fax: +358-9-191 51400
>> WWW: http://www.RNI.Helsinki.FI/~boh/
>> Journal of Negative Results - EEB: www.jnr-eeb.org
>>
>>
>
>


.