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Re: If Dinosaurs Could Fly
At 09:01 -0800 19/1/98, Terry D. Jones wrote:
>>I was amazed with Feduccia. I was waiting for him to put his fingers in
>>his ears and start shouting "I can't hear you". He said that he could see
>>no use for feathers as insulation? Feathers would be overkill if they were
>>for insulation? Does he think they just appeared on a protobird, intact,
>>out of the blue? Does he not believe in evolutionary steps? Does he think
>>that the link from (whatever he thinks) to birds has to be linear, with no
>>offshoots along the line? I wished they would have had him try to do more
>>explaining and less poo-pooing. Especially in the light of the three
>>specimens they showed.
>I think you're missing the point. Not all feathers serve an insulatory
>function. In modern birds insulatory feathers are down feathers, not
>flight/contour feathers. Down feathers are highly derived feathers.
Down feathers are extremely good insulators. This doesn't mean that
a less perfect insulator may not have evolved for that purpose.
Kiwi feathers are pretty good insulators even though they are not
'downy' at all, more like long thick hairs with a bad case of split
ends than down. Animal hairs serve well as insulation without the
need for them to be fluffy like down. Perhaps the original proto
feather was indeed some kind of thick hair used for insulation.
In fact I imagine the proto bird to look a bit like a kiwi, more
'furry' or 'shaggy' than bird like.
>feathers from which down feathers are derived functioned in flight, not
>insulation. This is part of the evidence that (in birds) powered flight
>evolved well before endothermy. There is a logical evolutionary progression
>from scales (in ectothemic avian ancestors) to flight/contour feathers (in
>ectothermic early birds) and finally to downy feathers (in later, enothermic
>[ornithurine] birds). In order to have insulatory feathers in the earliest
>birds they would have to appear intact out of the blue!!!
If it is true that 'down' is derived from complex flight feathers then
all this tells us is that the earliest birds didn't have 'down' of the
modern form. It doesn't follow logically that they didn't have
insulation, nor even that they didn't have a form of fluffy insulation
which would look like down to the casual observer.
Derek "How do you get down from an Elephant..." Tearne
Derek Tearne. --- @URL Internet Consultants --- http://url.co.nz
Some of the more environmentally aware dinosaurs were worried about the
consequences of an accident with the new Iridium enriched fusion reactor.
"If it goes off only the cockroaches and mammals will survive..." they said.