Re: Evolution, "adaptation", and what's currently adaptive
Len Piotrowski (lpiotrow@magnus.acs.ohio-state.edu)
Tue, 3 Sep 1996 21:39:40 GMT
In article <504muq$2pqm@argo.unm.edu> mycol1@unm.edu (Bryant) writes:
>[snip]
>>>>You haven't identified an adaptation, so I guess you've lost the bet. Their
>>>>"fitness effects" are only asserted.
>>>>They are just-so-stories.
>You're probably correct. We may never know the precise selective
>pressures which led to the evolution of sugar receptors on the tongue.
>But more generally, here's what dismays me about your apparent stance:
>You offer no alternative to natural selection for the creation of the
>functionally complex taste buds and brain modules for detecting sugar.
Connecting a "taste bud" to your "brain modules" is not as easy as invoking
the power of "natural selection." You gracelessly slip away from your original
assertion of "sugar craving" genes under the smoke screen of tongue receptors
and brain comparators. Why don't you stop this squirming about and allow some
resolution to a problem before you transmogrify it into "What I really meant
to say was ..." !
>Why did they arise?
What do you perceive as needing to be "arisen?" "Functionally complex taste
buds" or "brain modules for detecting sugar?" I have problems with your
presupposing descriptions for whatever these thingies are your trying
to validate as functional adaptations.
>Complex traits without selective advantage can, as you
>suggest, be maintained even in the face of mutation accumulation, if
>they're pleiotropically tied to some trait that is favored selectively.
Like survival of the organism as a whole ...
>But this does not speak to the *origin* of the trait.
You aren't concerned with initial origins of "sugar craving," nor sugar
receptors on the tongue, nor of "brain modules for detecting sugar," nor of
the brain. You're merely interested in maintaining this functional explanation
for all kinds of human behavior that resists such explication.
>Ultimately, you either concede the power of selection and look for
>testable ways to get at the trait's function, or you throw it on the
>dustbin of drift and hope you're right.
I suppose you can believe it's possible that every human behavior arose
through selection, but waiting a million or so years to derive it is
excessive. The nature of ongoing human action belies such a functional
fixation.
>>>Adaptations are traits shaped and retained by selection for their
>>>fitness-enhancing benefits. Hence, eyes are adaptations for seeing. Fair
>>>enough?
>>
>>Quite a eyeful that one. To rephrase the proposition: eyes are
>>adaptations because they see.
>Eyes are adaptations because they have design features unlikely to have
>accumulated by chance.
And too, unlikely to have accumulated as a sequential series of functional
adaptations with your final goal (to see) as the causal reason!
>They serve fitness-enhancing functions.
You don't know why "they" first appeared, or why "they" happened to be
retained, or if and when "they" served as " fitness-enhancing functions"
or for whom or what. This kind of story is about useless to illustrate any
principle you may be striving for in describing meaningful human behavior as
the result of functional adaptation.
>The only alternative to random accumulation in evolution is selection.
"Random accumulation" of what? This is getting more and more remarkable.
>>Offhand I would respond along several different
>>tracks. But chief among them, and most important to this discussion, is the
>>functional trope implied by this remark. Eyes are needed to see. Where did
>>the need to see come from?
>Selective pressures in the environment. Seeing shadows obviously
>provided early sighted critters (with their crude eyes) with some,
>perhaps slight, survival or reproductive advantage over the blind.
Just so ...
>>Another difficulty I have with tropes such as these is the idea that
>>structures like "eyes" somehow develop in isolation. If "eyes" have such
>>fitness value for "seeing" why do we not see eye organisms devoted to seeing?
>>A mammal without eyes is just as incongruous as a mammal without legs, or
>>hearts, or brains, or tongues with taste receptors. To parse the whole system
>>into separate pieces and talk about their individual affects on overall
>>fitness, and thereby use that exercise to account for why they appear their
>>in the first place, obscures processes and structures of relation and
>>interaction that represent the system as a whole.
>Because, Lenny, individuals aren't passed on.
I could quibble here about exactly who "passed on" if not Aunt Nell, but for
the sake of discussion, we're talking about the functional relevance of a
parsed part to a working system. The parsed part has no function outside the
system. In your own adaptationist world view, function has no value except as
part of goal directed system. Your model demands the "passing" on of goal
directed systems or it has no reason for persistence.
>Genotypes are not, either;
>they're broken up during meiosis.
You would concede they recombine to form functional wholes, now, wouldn't you?
Functional wholes that have prescribed fitness values!
>Ultimately, although selection acts on
>the individual for whatever net fitness his or her components offer in a
>given environment, only genes are selected for or against.
And so a problem source for the functional adaptationist point of view. The
system from which it was derived (the focal point of natural selection and
what is signified by "fitness") is nothing more than a hodge-podge of
individual traits, each viewed in isolation as a sequence of functional
necessities. Yet their very reason for being depends on their relationship to
the individual as a whole and it's needs and wants! How far is this from the
characterization by Gould & Lewontin of the adaptationist conundrum?
>Some are
>linked, but Mendelian inheritence takes us further than you suggest above.
Why don't you enlighten me as to what you think I've suggested above?
>>It doesn't change the fact the adaptationists employ functionalist
>>interpretations to explain the evolution of "traits." And besides, I haven't
>>seen any testing of the logical implications of your hypotheses!
>I haven't offered any.
Well thank you for capitulation to the obvious!
>If you would like to go over some examples of
>adaptationism that actually do, I'd be happy to go over them.
It would certainly be an improvement over your last "examples," but hardly of
interest to me, in as much as your original assertions made claim to an
explanation of certain aspects of human behavior!
>I've
>recently written a preliminary paper on the probable adaptations of baby
>cries and of postpartum depression in women. Would either of those be
>suitable?
Depends on what your ultimate claims are for this kind of behavior? Would you
concede a baby could have "learned" these cries, or at the very least,
re-organized control of it's behavior in order to decrease error from a
particular goal state whether intrinsic or sensed (hunger, thirst, or comfort
for instance)? Or must the baby have traveled the million year road to arrive
at this behavior? Could depression itself be a reflection of the failure of
the self-regulating mechanism to cope with abrupt changes in essential
physical properties, or intrinsic states of being? A kind of reaction to a
failure to "learn" or to re-organize a control system to cope with the change
in an intrinsic state? Or could it be a form of behavioral re-organization to
try and maintain goal values, or adjust intrinsic properties back to a
particular range?
>>>>The problem is with your definition of human behavior as "outputs of physical
>>>>phenotype."
>>
>>>Sigh. OK. So this boils down to a duelistic/spiritualist interpretation
>>>of the generation of behavior, then, Lenny?
>>
>>I have no idea what your talking about here. Care to elaborate on this theory
>>of human behavior? I can probably assure you without even hearing your
>>explanation that you will be far from the mark.
>I was asking if your comment about behaviors not being part of a
>phenotype meant that you think they arise from some non-physical entity,
I never made such claim. Your only recourse to a non-functionalist,
non-adaptationist explanation for human behavior can be described at the
very least as unimaginative, something you bewailed over in previous posts!
>as seems the only logical alternative to my posit, which you critique,
>that behaviors are the output of physical phenotype.
All I can say is that your's is not the only logic.
>Gotta run.
When you least expect it ...
Cheers,
--Lenny__
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