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In Defence of History (was Re: Exaptation and The Adaptationist
Danny Yee (danny@STAFF.CS.SU.OZ.AU)
Mon, 22 May 1995 14:30:22 +1000
Jonathan Smith writes:
> I consider Gould and Lewontin to be very much mistaken.
[ suggested readings ]
I've read the Mayr article and the older Dennett articles. I'm a
real Dennett fan, so I'd love to get hold of:
> Dennett, Daniel C.
> 1995 Darwin's Dangerous Idea: Evolution and the Meanings of Life.
Can you give me more information about this? Is it a paper or a new book?
I didn't read Gould and Lewontin as arguing against *all* adaptionist
arguments. As you point out, they use them themselves! Rather, the
centre of their argument is against the assumption that functional
arguments can explain everything. (This is similar to being able
to argue against narrowly functionalist views of culture without
rejecting functional explanation.)
> Lewontin & Gould heap
> scorn on all language related to adaptive function in evolution.
Maybe I read it oddly, but I think they are only "heaping scorn on"
*misuse* of adaptive language in evolution.
Mayer quote:
> Gould and Lewontin ridicule the
> research strategy: "if one adaptive argument fails try another one." Yet
> the strategy to try another hypothesis when the first fails is a
> traditional methodology is all branches of science. It is the standard
> in physics, chemistry, physiology, and archeology." (Mayer 1988 p. 151)
Sure, but that doesn't mean complaints about the use of ad hoc "just so"
stories should be ignored. It's one thing to try new hypotheses, it's
another to *assume* that a certain kind of hypothesis must work and then
fiddle parameters to get it to work.
> Dennett makes this point well in
> "The Spandrel's Thumb" (Dennett 1994 pp. 267-282).
Another Dennett work I haven't seen! Can you give me a full reference?
> In many important
> cases if the feature survives it is because it increases fitness. Once
> the feature increases fitness its survival can be understood using the
> adaptationist strategy, no matter how that feature originated. The
> adaptationist approach does not always work (some features are neutral
> and sometimes maladaptive features have not yet been removed from the
> population) but it does work in many cases and is worth trying.
But what about the importance of constraints? I always saw the core
of the Lewontin/Gould argument as the stress on the way existing
structures and historical patterns constrain the kinds of adaptations
possible. Sure, everything can be considered as an adaptation, but
if you want to understand why some "adaptations" happen and others
don't, then the constraints involved are at least as important as
the selective forces (whether one can separate the two is debatable,
of course!).
> Note that Lewontin & Gould are also proposing that certain
> features have no independent function, that they cannot be replaced by
> alternatives that make a difference in fitness. How do you go about
> testing a hypothesis of 'no function'? How do you test a spandrel?
If there are two features with equal fitness, one of them may be
"reachable" and one of them may not. This may not be testable in
the usual natural science fashion, because it requires essentially
*historical* reasoning, and is therefore just as difficult as arguments
about alternative historical possibities. That doesn't mean it's
not scientific, though!
> If we give up the adaptivist strategy in science the only stories
> that we can tell about the past will be to list is laborious detail the
> individual instances of selection and genetic change.
I don't think L&G think we should give up adaptionist strategies -- all
they are arguing is that there are lots of other strategies that are
productive and which should be used as well!
> Why does the butterfly have eye-spots?
Why did Rome defeat Carthage?
> Without adaptationism we can only list the
> long sequences of ancestors who managed to survive being eaten by
> individual animals and particular chance genetic changes and instances of
> exaptation.
> accept as an explanation is that eye spots increase fitness by serving as
> camouflage.
As an explanation we need both the historical detail AND the attempt
to sythesise broad causal explanations. Either one without the other
is weak. To say simply "the butterfly has eye spots because it helps
avoid predators" is only half the story -- the other half is why it
has those *particular* spots, which will probably/often require an
understanding of butterfly ontogeny, the geographical distribution of
the species when the spots evolved, and all sorts of other things.
Similarly, to answer historical questions we need to take into
account both the surface, overt causality (Scipio and Zama) as well
as the deeper understanding of a whole pile of other things (economics,
geography, ...). In some cases the evidence *just may not be present*,
and even where it is firm conclusions may be hard to draw.
(Note: I'm not arguing that all aspects of evolution are as
complicated/messy as history, but parts of it sure seem to be.
Some history is relatively simple, anyway :-)
> The point I want to make is that scientific knowledge is created
> for human use and shorthand terminology like 'food' or "camouflage' helps
> us write stories about our world.
Gould and Lewontin are rabidly anti-reductionist, so I'd have thought
they'd be the first to defend the use of terms like 'food' and
'camouflage'. (Cf. Lewontin and Levins, _The Dialectical Biologist_)
I certainly don't ever recall them arguing against such terms!
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Ralph Holloway:
> I was unfortunately present at S.J. Gould's James Arthur Lecture on
> the Evolution of the Human Brain a couple of years ago where I learned
> that language was just some epiphenomenon that grew out of brain size, a
> spandrel it was, this language, this cognitive faculty of ours. More
> crap. It will never explain why some microcephalics with brain sizes that
> match those of gorillas are nevertheless able to engage in true language
> behavior, albeit at a very reduced level of competence. I guess it is
> time to reinvent another wheel invented in the '60's. Ralph Holloway.
Gould does have a habit of exaggerating for effect (look at the mess
he got himself into by appearing to toy with saltationism in the
P.E. debate). But this sort of argument can not be dismissed out of
hand. I don't know about language, but it is impossible (for exmple)
that human ability to perform higher mathematics or write sonnets is
an adaption. It seems obvious to me that our brains evolved certain
general purpose intellectual abilities because of particular selective
forces (we had a debate on what these were in January -- tool-use vs
social interaction); these *quite fortuitously* allow us to do lots
of other things!
Danny Yee.
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