Linguistic theory and biology have long had a mutually
beneficial trade in ideas. Kai Jerne (here) explicitly cites
the influence of Generative Grammar on the way he approached the immune system
(here).
The Principles and Parameters (P&P) theory and the Monod-Jacob theory of
biological switches drank from the same stream of ideas and Chomsky has long
noted the similarity of his Rationalist take on biology to that of ethologists
like Tinbergen, Lorenz and von Frisch.
The most recent instance of the convergence/influence of
views comes with the rise of Evo-Devo (ED) adjustments to the standard
Darwinian story of natural selection. Here, I want to focus on one property of
such accounts that I believe carry an important lesson for grammatical theory;
the deep conservation of basic biological mechanisms. Let me explain with an
illustration.
One of the big unexpected ED discoveries concerned the eye. The
hero of this little tale is Walter Gehring (WG). Here’s a potted history of
what WG discovered (based on this very accessible paper (here) by Gehring and
Ikeo (G&I)). Prior to Gehring’s work the eye was the poster child for
analogous evolution; the idea you can get the same “organ” via different
evolutionary routes. Based on comparative and structural studies, the standard
account was that “the photo receptor organs … originated independently in at
least 40, but possibly up to 65 or more different phyletic lines” (371). The
basis for this view? The “obvious” physical differences between the different
kinds of eyes. G&I describes the state of play before Gehring’s work as
follows:
Their section
on ‘the multiple origin of eyes’ begins with the comment that ‘it requires
little persuasion to become convinced that the lens eye of a vertebrate and the
compound eye of an insect are independent evolutionary developments’. This
point has been taught to biology students for over a hundred years. (371)
This turned out to be wrong. In other words, despite the
evident surface differences among eyes in different species, nonetheless they
all are basic variations of the same basic design. Or put another way, these
different eyes all have a common ancestor, all stem from a common prototype,
the differences being bells and whistles added to shared basic design. In an
important sense then, there is only one
eye.[1]
Btw, before saying a bit more about this, it is worth noting
an interesting side comment that G&I make on Darwin’s views of natural
selection, specifically concerning the origin of the eye prototype. Here’s the relevant
wording:
Darwin was
highly self-critical in his discussion of the eye prototype and admits that the
origin of the prototype cannot be explained by natural selection, because
selection can only drive the evolution of an eye once it is partly functional
and capable of light detection. Therefore, selection cannot explain the origin
of the eye prototype, which for Darwin represents the same problem as the
origin of
life.
Therefore, both the origin of life and the origin of the eye prototype must
have been very rare events, and a polyphyletic origin in over 40 different
phyla is not compatible with Darwin’s theory. (371)
In other words, according to Darwin, the emergence of
prototypes cannot be accounted for in
terms of Natural Selection, rather Natural Selection presupposes such rare
events. No prototypes, no tinkering. Moreover, the emergence of prototypes must be very rare events. Sounds more
than a bit like Chomsky’s proposals for the origins of recursion doesn’t it? So
the next time you hear someone say Chomsky’s views are incompatible with
evolution (i.e. that the sudden emergence of Merge makes no evolutionary
sense), tell them to go and look up Darwin’s discussion of the emergence of the
eye.
Ok, back to the main point. What’s the new basic view of the evolution of
the eye? There is a master control gene responsible for all eyes that is shared across all sighted creatures from
Drosophila to mice to humans. In other words, there is really only one eye that
are based on the many of the same basic building blocks. P&P indeed!
Any implications of this for linguistic theory? Not
logical ones, but very suggestive ones.
Two in particular come to mind.
First, that “evident” surface differences in biology are not reliable signs of different mechanisms. This holds just as true (or should do so) in linguistics as in other
parts of biology. I have discussed this recently (no doubt ad nauseum) here
and here.
But the point is an important one given the temptation to believe what is right
before one’s eyes. This may sound like good common sense, but if science has
taught us anything it is that things that look
very different might nonetheless be exactly the same. In fact, what we consider
the highlights of scientific insight basically consist in showing that two
things that have entirely antagonistic properties are actually at bottom
identical.[2]
Second, that biology finds it very hard to truly innovate.
In other words, that there is basically only one way of doing anything. This
suggests skepticism whenever a linguistics paper suggests that more than one way
of doing anything. For example, there is a current view within syntax that
there are two very different kinds of relative clauses formed using two very
kinds of operations (matching vs movement). This view is buttressed by showing
that these two constructions have different properties and the inference is
made that such different properties require different kinds of operations to
explain them. That is, of course, one way to explain surface differences.
However, perhaps we should resist this inference until dragged kicking and
screaming to the conclusion.[3]
Why? Because multiplying mechanisms comes at the cost of explanation AND
because it looks like biological systems don’t like doing anything two ways. So
if you are a thoroughly modern GGer who understands the enterprise in cog/bio
terms then you should be reluctant to ever multiply mechanisms. In short, as a
general methodological rule of thumb, you should assume that there is only ever
one road to Rome.
The proliferation of theoretical mechanisms is an easy way
of covering apparently different properties. And, in fact, it is logically possible that variation
signals divergent mechanisms. However, the successful sciences, in particular
physics, has got to where it is by strongly resisting this mode of inference.
It was supposed that this might be good for physics but not for biology where
typically many mechanisms that can result in what look like the same effects. We
now know that this is not quite so at the smallest cellular levels and ED is
showing us that this is likely not even so at the macro level. Not only are
living things more or less the same in micro, but it seems that our macro
organs (e.g. eyes) are also built in more or less the same ways as well. I
suggest that we adopt the same stance within linguistics. Our regulative ideal
should be that FL/UG never does anything in two different ways.
[1]
Just as there is fundamentally only one language, or more precisely one FL. Or
put another way: impressive surface differences among languages do not imply
different underlying etiologies.
[2]
My good and great friend Elan Dresher once observed that there are really only
two kinds of theoretical linguistic papers. The first shows that two things
that appear radically different are more or less the same. The second shows
that things that are more or less the same are in fact identical. Yup.
I'd like to offer a measured dissent. (At least I hope it's measured.) I think the work arguing that there are two ways to derive relative clauses is extremely insightful; it's linguistics at (or near) its best. If someone can then come along and find a way to unify things, that's all the better (though skimming the Sportiche paper you linked to, he relies on a notion of "crash" at the interfaces, so color me skeptical). But we wouldn't even know that there was anything to unify if not for that work.
ReplyDeleteTo put this another way, in order to be impressed with Gehring's work you have to first appreciate the nontrivial surface-diversity that is at play. If I told you that every species that took closeup photos of Pluto did it in the exact same way, I suspect you wouldn't be as impressed.
So with all due respect to Elan Dresher's adage, I think papers saying "these two things that look like they're the same are really profoundly different" are very valuable (full disclosure: I've written one or two papers of this sort myself, so I'm obviously biased). First, it keeps the unifiers honest: after all, unifying is easy right up until you need to get the details right. Second, it tells us something about the range of things that our One True Mechanism is capable of generating, which I think brings us closer to – not further from – a proper understanding of that mechanism.
Oddly, I completely agree. Methodological ideals are not dispositive and maybe the case of RCs is one where it fails. However, it is a good general assumption, I believe, and one motivated by these biological discoveries (*or made more plausible by them).
DeleteSO why do I agree with your point? Because OF COURSE the right way of proceeding is via the HARD work of unification. It is always useful to look at where things LOOK like they differ for showing that they do not actually do so is an accomplishment. Showing that two things that look similar are indeed similar (or the same) is not something that one generally gets kudos for (rightly IMO). So, you are right that the advice does not imply that looking for differences is nugatory. Wghat it does endorse is the view that one should not be quickly satisfied that one has found two different mechanisms. One wants very high standards of proof for this conclusion. This is a standard minimalist trope: we want high burdens of proof from those that violate our methodological maxims. This is the theme of the 93 minimalist paper, and I believe that it still holds.
As for your skepticism re interface crash; I was expecting it and you may be right, though it makes for a very nice conceptual story.