Re: NS and AaD curves

g wrote:
> "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?

Maybe, but that's not the hypothesis: fitness tells us the expected (in
a mathematical sense) rate at which genes are passed on, not the actual
rate. (there's one poster here who defines fitness otherwise, but he's
not a biologist and doesn't understand a lot of what he fulminates
against, so we can safely ignore him). All these other random factors
are collected together as "genetic drift".

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.

That would be a change in the environment: fitness is defined to be
specific to an environment. If the environment changes, so does fitness.

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?

No. Luck. You're still assuming that fitness measures the actual
number of offspring. This isn't 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...
>
Change in environment: change in fitness!

<snip>
>
> 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.
>
Well, that's certainly true: of course, it immediately begs the question
"why is it the fittest?"!

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

.