Saturday, 5 May 2012

Birds before dinosaurs, fish before birds?

I am not a biologist or zoologist in any active sense (amateur or professional)  but do take an interest in the major developments. One thing I have always been sceptical about is the notion that birds descended from dinosaurs. This theory has almost become a dogma but the evidence is very sparse and the conclusions don’t follow.

Feathers have been found on certain dinosaur fossils and, like birds, they give birth via eggs but :

  • Fish also give birth via eggs

  • The body plan of birds is nothing like that of dinosaurs

  • Feathers could be evolutionary remnants from previously evolved birds

  • No truly intermediary species between bird and dinosaur has been unearthed. (The archaeopteryx is not generally accepted as fulfilling this role.)

It  seems more feasible to me, as a non-expert, for a creature to have made the transition from sea to air rather than land to air. Swimming in the water could surely have developed into swimming in the air. Fins could have become wings.  Could not the first birds have evolved from fish? Flying fish have aerodynamic characteristics like a bird and are able to stay aloft for up to 45 seconds.
 Evolving wings and a very light, but in relative terms immensely powerful, streamlined body to propel land-based organisms through the air and against gravity seems like a very big step. Fish already know how to glide, dive and propel themselves in a fluid. Given the inventiveness and intelligence of the natural world I can’t see why this possibility is rarely discussed in the scientific press.
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I was encouraged to see that some qualified researchers who have previously been ignored are beginning to get taken seriously for proposing dinosaurs from birds rather than birds from dinosaurs. See, e.g., Alan Feduccia’s Is it a bird? Is it a dinosaur? In the New Scientist, 28 April 2012. This does not propose fish as the starting point but it claims there is mounting evidence for birds having preceded dinosaurs.

Feduccia claims that Sinosaurotpery (see photograph above) ,the small fossil recently found in China, an earlier discovery of which was first described in Nature in 1998, was erroneously jumped upon as evidence for dinosaurs from birds. To quote: ‘ evidence then or now has emerged showing that these structures are anything other than collagen fibres supporting a typical reptilian frill. The fact that they were located within a clearly demarcated body outline ...was completely ignored.’ He also points out that 'current orthodoxy dictates that the entire suite of avian flight architecture, including aerodynamic wings and specialised brain structures, evolved in earthbound dinosaurs...’ To me as an outsider this does seem a stretch on credibility.

 It would all be a lot simpler if fossilised birds were found. Unfortunately, they are by necessity so finely constructed that they do not lend themselves to fossilisation, so we may have to wait for a clearer picture to emerge. It is a case of absence of evidence not being evidence of absence.  But this does seem to me another example of evolutionary biologists seeing what they expect to be there rather than what is in front of their eyes.

What gives me, with no training in biology or zoology or paleontology, the right to comment? Nothing. But sometimes people from outside the field can see things afresh or stimulate a professional scientist to think outside the box of the current dogma or say things which may risk prejudicing his career or credibility but which nevertheless need to be taken seriously.


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