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Re: Behaviour Bias



On Fri, 21 Feb 1997 02:12:48 -0500 (EST) Gothgrrl@aol.com writes:
 
>Endocranial casts allow us to determine the ratio of brain weight to 
>body
>mass, which is very, very important in determining "how intelligent" 
>an
>animal may have been (or be). Good endocranial casts also allow us to
>determine precisely how that intelligence might have manifested 
>itself, by
>demonstrating evidence of brain morphology (i.e., the size of the 
>optic
>lobes, frontal lobes, etc.). 

My problem is that there is no table or scale, in even extant animals,
that will predict what behaviors you can expect with a given ratio of
brain weight to body mass.  Even if you try this within a taxon, you
can't get a real "ladder" of intelligent behaviors that correspond with
the ratios.  I think you can make broad generalizations with the casts,
from the relative sizes of optic lobes, etc, but we have no way to tell
what behaviors were hard-wired, how flexible the learning capacity of an
animal was, or really how to compare these things relatively among living
animals.  An endocast is a very, very sketchy thing to base a rating of
intelligence on.

> Actually, octopus brains are rather large (the largest of 
>any
>non-vertebrate), both as regards absolute size and size relative to 
>body
>weight. Furthermore, despite there admittedly impressive intelligence, 
>they
>do not tend to behave like mammals and have no direct bearing on this
>discussion.<

I beg to differ.  NATURE's program "Incredible Suckers" showed an octopus
stalking and hunting its prey in a very complex and cunning manner, very
mammal like.  The law of parsimony says one should view this incident
with an alternative explanation; but the footage was impressive in
showing the planning, stealth, and "faking out" behavior the octopus did
to catch a mantis shrimp, and I for one was floored with the similar
techniques found in mammals.
>
>>But I think this is a normal "let's swing the pendulum way >over in 
>the
>other direction to compensate for that silly old >error" response. 
>Pendulums
>do swing back and find a nice >middle ground eventually.
>
>This is not exactly a prescription for good paleontology (or any 
>other
>science, ftm). See Thomas S. Kuhn's THE STRUCTURE OF SCIENTIFIC 
>REVOLUTIONS
>(1962, Univ. of Chicago Press).

Brother, can you PARADIGM?  No, it's not good science (I never said it
was), but people strive towards perfection.  They don't always hit it.  

>Because we can only reason from the evidence at hand. With dinosaurs, 
>that
>evidence is limited to fossils, which means we may only study 
>behaviour
>indirectly. While we can often draw broad ecological parallels between
>extinct and extant organisms based on fossil evidence, it is only very 
>rarely
>that we can soundly make more specific inferences (those rare 
>exceptions do
>exist and I'm not trying to discount them). 
>

Agreed


>It's safe to say that both _Allosaurus_ and _Felis leo_ are relatively 
>large
>(with regard to their respective prey species) terrestrial carnivores,
>preying primarily on terrestrial herbivores. After that, things begin 
>to get
>fuzzy, and the more specific our comparisons, the fuzzier they become 
>(for
>instance, if we were to say that allosaurs, like lions, are ambush 
>predators,
>or that, like lions, allosaurs must have hunted in cooperative 
>"packs").  

Yes, it's fuzzy (and not just because it's a mammal).  But if all you
have is animals today to work with, as long as you state how far out on
the limb you are going in your speculation, I still don't see why you
should just stop short.
I wrote: "But why limit yourself?"
You answered:
>Because I am a scientist and that's how I was taught to do science.>

Didn't Kuhn write that limiting yourself tends to squelch new paradigms? 
That new paradigms are created by going out on limbs and gathering data
to support it?  There has to be a balance, the data driving the theory,
the theory going into prediction, then we go back to get new data (or
relook at the old).

>I know of no direct evidence of _Deinonychus_ "packs" preying on
>_Tenontosaurus_, but this is not my area of specialty, and I may have 
>missed
>something.

My impression of reading John Ostrom's descriptions were that the fossils
pointed to the cooperative killing rather than scavenging, but this was a
long time ago and I don't remember how (or if) he eliminated the
scavenging option.

>How can we test a pack hypothesis? My guess is that it would be 
>extremely
>difficult, if not impossible, to ever conclusively demonstrate that 
>any
>extinct theropod species hunted in "packs." There are too many other 
>equally
>plausible explanations..... How, on the basis of a fossil association of
the mixed 
>remains of
>multiple individuals of _Deinonychus_ and a single _Tenontosaurus_ 
>......, do we
>distinguish between these two possibilities? Or rule out the 
>possibility of
>the ornithopod having expired from disease and then being discovered 
>by the
>theropods? Or that the _Tenontosaurus_ was killed by a larger theropod 
>that
>ate its fill and left the scene to scavengers (and while I don't think
>_Deinonychus_ *looks* like a scavenger, it may well have scavenged
>opportunistically). 

Agreed.  Even with theropod teeth imbedded in the bones, it could be
either scavenging by a pack, scavenging by individuals over time, or
hunting in any number of ways.  If paleontologists label this as
conjecture, it would help.  Many are misquoted by journalists that want
their stories to sound conclusive and exclusive.  But some
paleontologists don't say how shaky the evidence for their idea is right
up front in the popular press.  Is this because they want to attract
attention to their ideas specifically, or to just attract attention to
the field so all will benefit?

Judy Molnar
Education Associate
Virginia Living Museum
vlmed@juno.com
jamolnar@juno.com