Re: Bipedalism

["John V Jackson" <jjackson@interalpha.co.uk>]

-----Original Message---From: Rob Meyerson Date: 01 April 1998 09:30

< I wonder if bipedalism would be a detriment, and possibly fatal, for an
arboreal animal >

Bipedalism arises not from arborealism as such but from leaping - to other
branches, as opposed to what early birds probably did - to which an arboreal
lifestyle lends itself.  Interestingly this often leads to hopping, as in
kangaroos (whose ancestors arose from the largely forested Australia of
earlier times) and certain lemurs who can only progress on the ground by
hopping.

Then why do monkeys and apes retain a normal walking ability?  Well I
suppose hopping/leaping will only become obligatory if the animal returns to
the ground only very rarely, and then it may not happen (only some of
lorris's, potto's etc leap/hop, and many apes are too big to risk it).

Perching birds have adapted to grasping branches with their body at right
angles to the branch.  When they want to move about in a tree without flying
they cannot very well pace.  This is why they have started to hop.
Interestingly this use of hopping has no bearing whatsover on early birds
and bipedalism since their feet, their hands, and the trees they lived in
were different.  Trunk scaling would have been more central.

In general though, bipedalism is far from "a detriment, and possibly fatal,
for an arboreal animal "; indeed having hand claws that could not grasp
ancient trees trunks well would often have been fatal to small
thecodonts/early dinos.

JJ

Surely a true Yankee never says "Y'all" ?