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Re: Mats and boles, relatively? (bipedism)



If one views the biosphere through time, from zero hour to present, there is 
logically a point at which the only terrestrial vertebrates were effectively 
"sprawling quadruped(s)". It follows that the transition through vertical space 
from a condition of maximal vertebrate competition to minimal (i.e., zero) 
vertebrate competition was abrupt, possibly mere centimeters, and any small 
advantage in vertical reach could make a huge difference in the probability of 
reproductive success. 

This is an excellent reason for hauling one's self up on one's hind legs; or 
hauling one's self up a tree, or learning to fly, for that matter ... the 
advantage of vertical access has obviously been a huge driver of vertebrate 
morphology.

Don

[Sidebar -- I dimly remember reading a paper (published I think in the
'60's) that explored this idea of an early land of milk and honey mere 
centimeters over your head, and it's effect on vertebrate evolution, but can't 
remember the author. Hell, I am not totally sure I read such a paper; does this 
concept ring a bell w/ anyone, so I can get a re-read?]

----- Original Message ----
From: "Dinogeorge@aol.com" <Dinogeorge@aol.com>
To: VRTPALEO@usc.edu
Cc: Dinogeorge@aol.com; george.olshevsky@gmail.com
Sent: Saturday, November 17, 2007 10:48:33 PM
Subject: Re: Bats and moles, relatives? (ptero launch)


In a message dated 11/17/2007 6:19:04 P.M. Pacific Standard Time,  
tijawi@yahoo.com writes:

>>Another reason (much better supported) why birds never lost  their 
hindlimbs as locomotor organs is because, as theropods, they are
 descended  from 
bipeds that came to use their forelimbs for aerial locomotion.  As
  theropods 
developed flight, their hindlimbs never deviated from their ancestral
  function in 
bipedal locomotion. <<  


How did this  "ancestral biped" come into existence? What sequence of 
selection events caused  a sprawling quadruped to haul itself up onto
 its hind legs 
and start walking and  running around?
 



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