Re: Bird Brains

[Mickey Rowe <rowe@psych.ucsb.edu>]

Daniel Bensen <dbensen@gotnet.net> wrote:

> Mammals evolved in the Triassic birds evolved in the Jurassic (yeah,
> the Jurassic, those BCF people can bite, er, peck me).  

In my official position as an owner of this list I'd like to remind
one and all that the purpose of this list is to house discussions
about dinosaur science.  Comments such as that in the parentheses
above have no place here.

> So mammals have been around longer than birds.

In my unofficial position as a subscriber to this list let me address
this statement as a matter of fact.  "Mammal" and "bird" are
vernacular terms; "mammal" is generally understood to refer to the
class "Mammalia", but what "bird" refers to is frequently a subject of
debate right here on this list.  Stepping back further, though,
whatever animals the categories "bird" and "mammal" encompass, the
categorization can either help or hinder your thinking about
particular questions.  In this case, it appears to me that Dan is
being hindered because he's focusing on an arbitrary detail rather
than a more general appreciation for the history through which the two
respective lineages have evolved.  The K-T extinction event was a
major episode for both birds and mammals, but for mammals it
represented an opening up of niche space previously occupied by
dinosaurs.  In some ways relevant to the discussion at hand, surviving
bird lineages represented more of a continuation than a radiation.
This is, of course, a major oversimplification, but it speaks to the
issue more directly than did Dan's response.

Dan also wrote (first quoting: Antony L Hedges
<boner@boner.screaming.net>): 

>> so it would stand to reason that, with longer to evolve some of
>> their systems are going to be more advanced/efficient.
>
> Um, no.  Evolution doesn't work that way.  (read Steven Gould)
> organisms become better adapted for their environment only in the
> most scattershot and shortsighted manner.

Even if Dan's statement were correct it would not negate Tony's
contention.  If you have two blind men stumbling in a generally
northerly direction, the one that started thirty years ago is probably
going to be closer to the North pole than the one that started two
years ago provided they started from reasonably similar latitudes.

> The only reason, for instance, that sharks and cockroaches have been
> around for longer than mammals had, is not because being older, they
> are more advanced,

That wasn't the point.  To make the analogy more appropriate you'd
have to ask something along the lines of: are sharks better at finding
comestible meat in their environment than, say, whales are by virtue
of the fact that they've been living that lifestyle for a much longer
time?  In some ways sharks are definitely better.  Electroreception is
a great way to find animals in sea water.  In some ways they're not.
Sonar is a similarly useful (albeit less specific) tool.  Here is
where you have to start asking questions like: would whales develop
electroreception if given more time in the ocean to stumble onto it?
Do sharks not have sonar because given their other resources for
finding food it wouldn't be worth the cost or because, for example,
the contingencies of their long history never gave them a swim-bladder
or other air-filled organ which could have been co-opted for sound
generation and amplification?  Similarly, do sharks have
electroreception because they have had a long time to develop such a
capacity or were they preferentially predisposed to develop such a
system hence making the length of time issue moot?  Questions like
this are much easier to ask than to address with relevant data, so
beware of anyone who pretends to know the answers.

Turning back toward the original question... have birds had more time
to develop efficient neural processing strategies under conditions in
which those strategies would be adaptive?  How would you address such
a question?  You might start with Nick Longrich's
<nrlongri@midway.uchicago.edu> suggestion that "bright[ness]" is
associated with intra-specific social grouping.  Did dinosaurs form
cooperative groups?  Around here that question has been even more
contentious than the question of what is a "bird".  Turning closer to
the original question, has efficiency been selected for in bird
brains?  Probably -- birds are the only animals I know of which (at
least in some species) periodically "shed" part of their brains.  In
any case, we know relatively little about the "wiring" in bird brains.
Over the past 20 years we've found out a lot about the song production
structures in the brains of passerines, so it would not be fair to say
that we are completely clueless about how bird brains are wired, but
there are a lot more people studying mammalian nervous systems than
people studying avian nervous systems.  That's because one of the
major reasons people study other animals is to find out about
ourselves.  Birds are less interesting than mammals in that respect
because their brains are so different from ours.  Birds share with
mammals a relative expansion of the neocortex relative to the size of
that structure in the brains of animals from other groups, but they
appear to have gone through that expansion independently of mammals.
Most of the primate neocortex is functionally linked to the analysis
of visual information.  Is that also the case in birds?  I don't
really want to go on record (i.e. I'll defer to anyone who can refer
to hard data) but I don't think so.  Relative to mammals, reptiles
process much more of their visual information in the mid-brain.  Birds
are apparently not an exception to that rule.  Is their processing
more efficient?  I don't think we have enough of the right sort of
data to say.  But we can say it's different.

-- 
Mickey Rowe     (rowe@psych.ucsb.edu)