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Out of Thin Air: Dinosaurs, Birds, and…
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Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere (2006 original; edició 2006)

de Peter Ward (Autor)

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923292,131 (3.93)Cap
Discusses the effect of changing oxygen levels in Earth's atmosphere on evolution and mass extinctions, and presents the theory that saurischian dinosaurs were able to weather two mass extinctions because of a new, more efficient respiratory system, which was in turn inherited by their descendants the birds.… (més)
Membre:ElentarriLT
Títol:Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere
Autors:Peter Ward (Autor)
Informació:Joseph Henry Press (2006), Edition: 1st Edition., 296 pages
Col·leccions:La teva biblioteca, Llegint actualment
Valoració:****
Etiquetes:science-prehistory

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Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere de Peter Ward (2006)

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Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere by Peter Ward hypothesizes that changing atmospheric and oceanic oxygen levels over the last 600 million years have caused significant evolutionary development, including changes in body plan (morphology), physiology and diversity of animal life.

The author hypothesizes that with high levels of atmospheric oxygen, animals can grow very large, and do so because it protects them from predators. When oxygen levels drop, extinctions occur, and the numbers of organisms of any surviving species drop, but body-plans proliferate as species strive to adapt. More than any other required resources, oxygen is absolutely necessary for the survival of animals, their ability to meet the requirements of survival, and their ability to reproduce successfully. As atmospheric oxygen levels have fluctuated over geological time, evolution has followed suit, with mass extinctions and certain evolutionary radiations occurring as oxygen dropped, and more evolutionary radiations occurring once oxygen began to rise.

I found the material in this book fascinating, informative and thought provoking. The author provides many testable hypothesis and well as a large number of examples involving the structure and comparative functioning of lungs, gills, livers, feathers, hearts (four-chambered vs three chambered), bones, types of metabolism (endothermic vs exothermic), reproductive strategies (eggs vs live-birth) and body posture (bipedal vs lizard and mammal quadruped) in various atmospheric conditions. The impact of plate tectonics and geochemistry (sulfur and carbon cycles) on oxygen levels are also explored. The illustrations were also helpful.

This book is written for intelligent adults and assumes that the reader has some knowledge of the various branches of science, such as biology, physics, chemistry, climatology, and geology.

Overall, a good book and quite insightful, but an editor would have been useful to smooth out the occasional clunky language. I hope the author updates this book with new information soon. ( )
  ElentarriLT | Mar 24, 2020 |
Author Peter Ward has the answer for every paleontological question: oxygen. In this book, he marches through geological time from the late Precambrian to the Holocene, explaining just about every evolutionary radiation or extinction in terms of atmospheric oxygen concentration (with an occasional nod to carbon dioxide concentration, sea level air pressure, sea level, and climate). Ward presents us with a long series of hypotheses based on oxygen levels, such as:


Hypothesis 2.1: Reduced levels of oxygen stimulate higher rates of disparity (the diversity of body plans) than do high levels of oxygen.”


And


Hypothesis 8.1: The initial dinosaur body plan of bipedalism evolved as a response to low oxygen levels in the middle Triassic. With a bipedal stance the first dinosaurs overcame the respiratory limitations imposed by Carrier’s Constraint. The Triassic oxygen low thus triggered the origin of dinosaurs through the formation of this new body plan.”

And


Hypothesis 9.5: The crab’s body plan evolved for multiple reasons but one was that it increased respiratory efficiency by putting the gills in an enclosed space under the cephalothorax (the head-thorax) and then evolving a pump to move water over the now enclosed gills.”


Interestingly, every one of Ward’s hypothesis turns out to be confirmed when compared to a chart of oxygen levels through time.


So how does one go about measuring paleoatmospheric oxygen concentration? Well, that’s the trick – Ward doesn’t measure anything. The convincing-looking chart of oxygen level versus time is not based on measured oxygen levels, or even proxies for oxygen levels (such as the mineralogy of paleosoils). Instead, this is the output of a series of computer programs – GEOCARB, GEOCARB II, GEOCARB III, and GEOCARBSULF – that estimate oxygen concentration based on assumed past geological conditions – how much sulfide-containing rock was subaerially exposed to oxidation by tectonics, how much was subducted to be re-emitted as hydrogen sulfide (and then oxidized) during volcanism, and how much organic carbon (coal, oil shale, etc.) is buried before it could be oxidized. That doesn’t sound at all familiar, does it? An elaborate computer model used to predict (or, in this cast, postdict) atmospheric conditions? In short, what Ward is doing here is drawing conclusions far beyond what the model(s) justify.


Now that I’ve got through jumping on Dr. Ward with both feet, I have to backtrack. There is paleontological and mineralogical evidence that the Earth’s atmosphere had a different composition in the geological past. In particular, the existence of 50-pound scorpions, spiders with a 36-inch leg span, and 2-foot long cockroaches in the Carboniferous suggests something quite different from modern conditions. Arachnids have a pretty inefficient gas exchange system, and insects are even worse – thus it’s fairly certain that oxygen concentration – or at least oxygen partial pressure – was substantially higher then. (The Carboniferous would be a bad place for time-travelers uncomfortable around creepy-crawlys. I would sign up for the trip in a heartbeat, of course – but I think I’d probably bring a shotgun and a lot of DDT) . Similarly, evidence continues to accumulate that the atmosphere and oceans were strongly affected by whatever caused the PT extinction event – runaway global warming due to atmospheric methane or massive hydrogen sulfide releases from the oceans or a combination thereof.


Historical geology has had to be dragged kicking and screaming away from the idea of rigid uniformitarianism – the belief that Earth processes have always been exactly the same as they are now, and have always acted on a human time scale. Alfred Wegener was the first to make a dent here, with continental drift. Wegener’s details about continental drift were mostly wrong – the idea that the mechanism was some sort of arm-waving “polar flight”, and the belief that the whole process had stopped in the Pleistocene – but the big picture was correct. Similarly, although I suspect Dr. Ward is drawing way too many conclusions from computer models, the overall idea – that atmospheric and oceanic gas concentrations and partial pressures could have been different in the past and that this would have substantial impact on earth and life history – is likely correct, and Ward deserves credit for drawing attention to it. ( )
  setnahkt | Dec 16, 2017 |
Does a very good job in making his point about the influence of oxygen levels on evolution. ( )
  stevenwbucey | May 25, 2007 |
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Discusses the effect of changing oxygen levels in Earth's atmosphere on evolution and mass extinctions, and presents the theory that saurischian dinosaurs were able to weather two mass extinctions because of a new, more efficient respiratory system, which was in turn inherited by their descendants the birds.

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