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Re: Tyrannosaur age-population distributions



--- Phillip Bigelow <bigelowp@juno.com> wrote:

> If you look at the E.Q. (encephalization quotient)
> for tyrannosaurids and
> the E.Q. for chickens (and the E.Q.s for *all*
> living birds, in fact),
> you will find that _T. rex_ adults lag behind all
> extant birds in the
> Brainiac Department.
> 
> Robert Carroll's (1988) _Vertebrate Paleontology and
> Evolution_ textbook
> has a graph showing the E.Q.s of the various
> relevent taxa.
> 
> Then there is the quantum jump between the E.Q. of
> extant birds and the
> E.Q. of carnivorous mammals (like pack-forming
> animals.  Lions, for
> example).
> 
> _T. rex_ is "brainier" than crocs (and most
> herbivorous dinosaurs), but
> that isn't saying much.  Most of _T. rex_'s brain
> volume was taken up by
> the animal's sensory subsystems (olfactory lobes,
> and to a lesser extent,
> its optic lobes).  But for complex social
> interactions, a larger cortex
> is needed and _T. rex_ just doesn't measure up in
> that Department.

++++++++++++++++++++++++++++++++++++++++++++++

I'd be careful about using EQ as a necessity for any
complex behaviour. EQ in general, is still fairly
controversial and remarkably subjective (the main
impetus behind the numerous ways that EQ gets
calculated, seem to be based on keeping human beings
on top).

Furthermore, the most complex non-human social systems
out there (our closest rivals) come from social
insects (esp. ants). These are animals that don't even
have true brains. 

Though it's tempting (and often an overused crutch) to
say that their complexity is strictly the result of
instinct, the facts rarely bear that out. 

Some of the best examples to the contrary come from
the work of James & Carol Gould (e.g. the book: Animal
Minds). Both honeybees and ants need to convince their
peers to do something (e.g. flying out to collect
nectar, or helping their sisters who are being
attacked from afar). They don't simply release a
pheromone and go about their business. Often times the
communication involves various forms of pantomime
(e.g. the famous bee dances), in order to convey the
message.

A lot of what seems to be driving this complexity,
appears to be the result of simple communication
between individuals. Entemologist Jennifer Fewell did
some research on this (with bees if I remember
correctly), and found the same simple communication
between bee, or termite sisters, that lead to their
complex associations, was also found in people. Her
evidence suggested that big brains are not really a
pre-requisite for complex social activities.

I'm not really a big fan of pack hunting in any
theropod (given the rarity in most vertebrates today),
but given the plasticity of intelligence in creatures
with a wide array of brain sizes, I wouldn't rule it
out.

Jason

Shrews hold 10% of their mass in their brain (compared
to 2% in humans). All hail the shrew.

"I am impressed by the fact that we know less about many modern [reptile] types 
than we do of many fossil groups." - Alfred S. Romer

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