[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: flying Archie

Graydon wrote:

> What we've got is an environmental disjunction, with pronounced
> bottlenecking across the boundary.  If the archie-style fliers continued
> to prosper up to that disjunction, presumable what we've got is a
> combination of bad luck and the environments for which the long-tailed
> flight style was preferable not being available for a time as a result
> of that disjunction.  (and all it has to be is long enough to starve to
> death, as per Jim Cunningham's pterosaur extinction hypothesis.)

There is an alternate hypothesis in the case of birds.  Let us presume a
modification of the brain that reduces the need for flight stability.  That
reduces selective pressure to maintain the long, draggy old-style tail
(which was an asset before the brain modification).  Consequently, the tail
will become more variable with some being shorter.  That increases
maneuverabilty and the potential for prey capture, or food acquisition by
whatever means.  That increases selective pressure to maintain the shorter
tail, and that in turn increases selective pressure to be able to move that
shorter tail in ways that generate tail moments (command authority).
Presto, ain't too long before you've got pygostyles and long tails have gone
by the wayside.  That, in turn, opens up an avenue that allows redevelopment
of long tails based on the modern style, for display purposes.JimC