Taking Wing: Archaeopteryx and the Evolution of Bird Flight in Science and Inquiry

Feb 26, 2012 Steve Van Slyke rated it it was amazing

Shelves: evolution, science

Is Archaeopteryx a bird, or is it not? Could it fly or glide or neither? Was it descended from the dinosaur line, the crocodilian line or some other line? Did feathers initially evolve for flight or some other purpose? Did flight evolve from the trees down or the ground up? There have been a blizzard of scientific papers on these and related topics since the first fossil specimen was identified just two years after Darwin published On the Origin of Species.

One of the things that makes this book Is Archaeopteryx a bird, or is it not? Could it fly or glide or neither? Was it descended from the dinosaur line, the crocodilian line or some other line? Did feathers initially evolve for flight or some other purpose? Did flight evolve from the trees down or the ground up? There have been a blizzard of scientific papers on these and related topics since the first fossil specimen was identified just two years after Darwin published On the Origin of Species.

One of the things that makes this book interesting is that it is not by one of the researchers who might have too much skin in the game to be objective about other points of view. Pat Shipman is a paleoanthropologist who took an interest in the subject and thanks to her we don't have to wade through and digest stacks of research papers. She has provided us with a thorough summary of the state of research up through 1998, much like an impartial judge reviewing the evidence from opposing factions. There have been a few fossil discoveries since then, (four more Archaeopteryx plus possibly feathered dinosaurs) but I feel the book still provides a very fine overview and a sound basis for evaluating the latest reports.

Archaeopteryx is in the subtitle and it provides the focal point, as it should, but “Taking Flight” or, the evolution of flying, is the real topic of the book, and be forewarned the author is quite thorough about this. She even starts with explaining why humans can't fly, which seems obvious, but the technical reasons and the comparison with birds is interesting. We then dive deep into bats, pterosaurs, and insects.

She briefly mentions flying fish but they were usually excluded when she and/or the researchers talked about flying vertebrates. Flying fish should certainly be mentioned when talking about the feasibility of the “ground up” evolutionary route to flying for flying fish clearly do not glide down from trees. I have spent hours at sea watching flying fish accelerate from below the surface and then leap into the air, gliding sometimes for several hundred yards. Clearly, a ground up, gliding style of flying is possible. Another thing that flying fish demonstrate is that flying is useful as an escape mechanism from predators. Although the book mentioned escape as a possible evolutionary motive for attempts to fly it was overwhelmed by the view that flying was motivated more by enhanced means of predation.

My only other complaint about this marvelous book is that there was too little attention given to the aerodynamics of the running takeoff as opposed to the standing takeoff. Much was said and documented about the flight muscles and their ratio to total body weight, wing area, etc. And although there was a brief discussion of ground speeds necessary for takeoff, there was little or no discussion about the contribution of leg muscles to the takeoff equation. It seems to me that in a running (or rolling) takeoff, as the wings begin to generate lift, they automatically remove some of the load from the legs which then can drive the flier even faster. Archaeopteryx seems clearly to have descended from small, fast-running theropod dinosaurs, so it seems not unreasonable to have expected more technical discussion on these points.

By the end of the book Ms. Shipman has become converted from the impartial outsider to one who now has specific opinions of her own wants to be involved in the ongoing research. And she mentions that she sees areas of missing research, perhaps even my such as my takeoff questions. I hope to hear more from her in the future.

Besides being a wonderful story about the evolution of flight, this book is a perfect example of the beauty and process of science with all its warts, tiffs, and “wild goose chases”. It would be a great motivator for a young person considering a career in almost any scientific discipline.

Finally, each reader, after absorbing all the evidence, gets the opportunity to create in his/her mind their own conception of Archaeopteryx. Here's mine. I side with those who believe that it was descended from fleet-footed theropod dinosaurs similar to the contemporaneous Compsognathus, whose fossils were frequently confused with those of Archaeopteryx. And given that all of the fossils thus far found have been in the Solnhofen limestones of Germany, which were originally laid down in shallow lagoons edged by arid, shrubby islands, it seems parsimonious to assume that these creatures lived near the waters they eventually died in. Combined with the rest of anatomical and aerodynamic evidence, I envision Archaeopteryx as a cross between a shorebird and a road runner that could fly only short distances at mostly low altitudes by taking a long running takeoff followed by a combination of gliding and inefficient flapping. This would have served it well for both hunting of flying and scurrying insects as well as escape from theropod relatives trying to make a meal for themselves.

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