Monday, July 7, 2014

On the Origin of Feathers

The most recently described specimen of Archaeopteryx,
found in limestone deposits in Germany.
As the debate over the origin of flying birds continues, the ever-enigmatic Archaeopteryx pokes more holes on some theories while appearing to promote others.  As the “earliest” known flying bird, its combination of dinosaur and bird characteristics has long made it an icon of evolution, particularly for those promoting the idea that birds evolved from maniraptoran dinosaurs.  Currently, the general consensus of the scientific community is that Archaeopteryx was not the ancestor of modern birds, but a close relative of that ancestor—an early experimental evolutionary offshoot, if you will.  It is also generally accepted that it was capable of some form of flight, though possibly not as graceful as modern birds.

Eleven Archaeopteryx specimens have been described in scientific literature, all found in the Solnhofen Limestone in Germany.  The Solnhofen Limestone is a “laggerstätte,” a rock deposit that preserves small details in fossils.  In this case, the limestone has preserved the impressions of feathers in a number of Archaeopteryx specimens.  Paleontologists have studied these feather impressions for years trying to deduce their evolutionary origin.

The evolution of feathers is a difficult hurdle.  After all, feathers are a prerequisite for flight in birds, yet there is no obvious advantage to having feathers before flight evolved, so the feathers themselves have no reason to appear in the first place.  To surmount this problem, many paleontologists have speculated that feathers initially evolved as thermal insulation or as display mechanisms before being repurposed for longer jumps, gliding, and eventually flying.  However, such hypotheses are difficult, if not impossible, to test scientifically.

A group of scientists from Munich, Germany, think they have found evidence that supports the “display before flight” idea.  Studying one of the most recent specimens of Archaeopteryx, they have found impressions of leg feathers which do not appear to have been useful for flight.  In conjunction with the fact that other flightless dinosaurs have been found with feathers in various regions, the scientists argue that the feathers therefore must have evolved separately from any flight-related activity, most likely for display purposes.  They then further argue that the feathers were re-adapted for flight several times on different evolutionary branches, eventually resulting in modern birds.

First, let us not mistake this find as evidence for the evolution of feathered birds from unfeathered dinosaurs.  The case made by the authors assumes that such evolution occurred, and they interpret their finds in the context of this basis.  If birds are the evolutionary descendants of dinosaurs, then indeed the authors make a solid case for the preliminary use of feathers and their subsequent adoption for flight.  However, the mere presence of non-flying feathers in a flying creature does not indicate an evolutionary history of life on the ground.  Likewise, the presence of feathers in other therapod dinosaurs is not unequivocal evidence that they gave rise to birds.

How is a creationist to view such specimens?  As I have said before, it appears to me that God created animals across a nearly continuous and multidimensional spectrum, which I believe atheistic worldviews misinterpret as evolutionary relationships.  Attempting to draw a distinct line between birds and dinosaurs may do more harm than good, as such a classification is quickly rendered impractical due to the similarities between certain members of each group.  Moreover, the Bible gives very little to no basis for such broad categorizations, as organisms were created according to intrafertile kinds and are not grouped into larger morphological categories.  Admittedly, the Bible does distinguish between “birds of the air,” “beasts of the field,” “creatures that crawl along the ground,” and others.  However, these appear to be descriptions of modes of life rather than morphological classifications.  I think it may be more worthwhile to discern which creatures were in the same baramin (created kind) as Archaeopteryx than to attempt to force Archaeopteryx and other “dino-birds” into either the dinosaur or bird categories.

2 comments:

  1. No non-bird dinosaurs have ever been found with unambiguous evidence of feathers, so your article is being misleading by implying that there have.

    ReplyDelete
  2. "I think it may be more worthwhile to discern which creatures were in the same baramin (created kind) as Archaeopteryx than to attempt to force Archaeopteryx and other “dino-birds” into either the dinosaur or bird categories."

    I completely agree. I think some creationists try too hard to make dinosaurs as un-bird-like as they can. For instance, most major creationist ministries(including AiG,CMI,ICR), have a feather-based critera to differientiate dinosaurs and a bird. While I too used to think this way, this idealogy doesn't make sense to me now, as it leads to some very strange taxonomic grouping. For instance, AiG considers Velociraptor a dinosaur, while Microraptor and Zhenyuanlong are considered birds, despite the fact that all three creatures are more similar to each other than they are to any other bird or dinosaur and probably belong to the same baramin. Why should feathered dromaeosaurs be considered evidence that birds are dinosaurs any more than red pandas being considered related to giant pandas and raccoons. Finding feathers on a dinosaur doesn't tell us how feathers evolved in the first place, so they're still problematic for the evolutionist. Don't get me wrong, I love the work and research AiG, CMI and ICR are doing, but I don't agree with their stance on feathered dinosaurs.

    ReplyDelete