RE: FUCHSIA and the Ostrom Symposium Volume

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Colin McHenry wrote:

> Errmm, isn't the basic axiom of cladism based around the (logically
> untenable) assumption that evoultion follows the path that's "easier"
> (i.e.most parsimonious)?


I was speaking in a biomechanical context, not a phylogenetic one.  To give
an example: as pointed out on numerous occasions, it's easier to evolve
flight from an elevated vantage point (such as a tree branch) than from the
ground.  With the former "trees down" scenario, the flier can use gravity to
its advantage to generate airspeed and lift.  From the "ground up", by
contrast, the flier is working against gravity from the very beginning.  So
evolving flight from the "trees-down" is 'easier' than evolving it from the
"ground up".

Big deal.

As long as evolving flight from the "ground up" is biophysically (and
biomechanically) feasible it cannot be marshalled against a "ground-up"
scenario.  The final arbiter is phylogeny - specifically the sequence of
character acquisition leading up to flight.

(As it happens, I happen to believe that the fossil record favors a
gravity-assisted "trees-down" scenario for the evolution of avian flight.  I
also apologise for dredging up the old "ground-up" vs "trees-down" dichotomy
in the evolution of bird flight - I was just using it as a convenient
example.)


David Marjanovic wrote:

>  On the other hand, regarding good old Archie... it didn't run much, 
> it climbed even less, it lived on rather food-poor islands, 

I'd love to have a ride in your time machine.  Pencil me in for next week -
I'll bring a notebook, and I'll see if I can make the same observations that
you did on _Archaeopteryx_'s behavior.  I'll even bring a pair of swimming
trunks, in case you're right.



;-)



Tim