Re: Theory Sez Flight Evolution Linked To Parental Care

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Patrick Mellor" <patrickmellor@hotmail.com>
Sent: Wednesday, January 30, 2002 9:07 PM


> Endothermy evolves solely for brood care, hard to see the selective
benefit
> in that.

Why? The young grow up in a continuously warm environment, so they can grow
fast and continuously. A relatively old idea (I once cited an SVP meeting
abstract onlist).

> >Scales
> >evolved into feathers, better camouflaging and insulating the parents.
> >
> >In time, these early ancestors of birds developed more advanced
techniques
> >for caring for their young. ...
> >
> >Gradually the forelimbs of these creatures became feathered and even more
> >elongated, enabling them to better manipulate their eggs and to
> >"parachute"  from their tree nests to a soft landing. Later they would
> >develop the ability to glide and eventually fly by flapping their wings.

The sequence parachute --> glide --> fly is of course deeply flawed.* Why
not extend the feathers-for-brooding idea into wings-for-brooding (HP Hopp &
Orsen 1998 etc.)?

* Not that I had any idea about how bat flight evolved... :-] But they can
certainly have started right with gliding and skipped the parachuting stage
and the difficult parachute-glide transition.

> >He adds that the fossil record, specifically Archaeopteryx, provides
ample
> >evidence that the evolution of parental care was the main driving force
> >behind the evolution of avian flight. For example:
> >
> >* Fossil specimens of Archaeopteryx have forelimb claws,

Here one sees an enormous disadvantage of Class Aves. "Oh, it is a bird, but
what an UNUSUAL bird! It has claws on its free fingers!!! How PECULIAR! That
must be a very SPECIAL ADAPTATION!!!" -- as if it were an apomorphy instead
of a plesiomorphy. How I hate that. <grrr, grumble, grumble>

> >* The feathers on Archaeopteryx fossils appear to be much more advanced
> >than the creature's other birdlike traits, which is consistent with the
> >notion that feathers evolved very early to shield the nest-sitting adults
> >>from the elements;

Well possible.

> >* The beak of Archaeopteryx is quite primitive,

It has a beak at all? News to me.

> >* While Archaeopteryx had highly advanced feathers, its bone and muscle
> >structure appear to have equipped it for only limited flight.
>
> wasn't archie quite a competent flyer?

Was Archie a flyer at all, considering its almost asymmetrical wing
feathers?

> This makes
> >sense, according to the parental care theory,

tss, tss... hypothesis

> >which asserts that flight
> >developed long after the reptiles with their protective feathers moved
> >into the trees.

Which, in turn, looks like it disagreed with what we know of the fossil
record. Only *Sapeornis* + Pygostylia among described taxa have e. g. a
long, reverted hallux, suggesting to me that they first learnt to fly and
then flew up a tree. But I haven't read any more about Dial's wing-assisted
running hypothesis than what has been written onlist.

> feels a bit like a just so story to me...

=8-)
But with a fossil record like that just about all evolutionary scenarios are
indeed just-so stories.