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Re: a challenge to the cladists



At 02:15 PM 12/3/96 -0500, Bonnie Blackwell, x 3332 wrote:

>I still for all the discussion of cladistics over the last year - and
>believe me that has been alot - fail to understand why cladists choose
>to ignore an important variable in their analysis.  And given that
>most paleontologists doing cladistics are trained as geologists, this
>is a failing i really find hard to understand.  WHY DO YOU CHOOSE TO
>IGNORE TIME?  It's not as if time is a variable that is obscure.  We
>all know that Albertosaurus and Tyrannosaurus did not live at the same
>time, yet the cladistic analysis completely ignores this variable.  It
>is an easily defined characteristic of the species.  It provides a
>reference frame within which to hang the morphological
>characteristics.

   I'm not a cladist by any means, but my *assumption* is that the reason
time is "ignored" is because it cannot be guaranteed that the fossils first
appearance in the record actually is when the creature evolved.
Dromaeosaurids are a good example ... they're mid to late cretaceous, yet
every time I see Norell or Novacek on Nova or somesuch, they're saying the
probably evolved some time before.

>To me - granted humble geochronologist - this
>seems like deciding to analyze motion by only considering distance
>thereby ignoring time (makes it very hard to consider acceleration,
>speed, etc.)

   Unlike with motion, time can largely be assumed when considering
evolution, I would think.

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