Customer Reviews

Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere

5 star:		(3)
4 star:		(8)
3 star:		(2)
2 star:		(0)
1 star:		(0)

 

 

Mountain climbers struggling to breathe astride the 29,029 foot (8,848 meter) summit of Mt. Everest routinely see birds gracefully flying above them, engaging in nonchalant aerial acrobatics at altitudes where humans risk hypoxia (oxygen starvation) while standing still.

The avian respiratory system is at least 33% more efficient than any mammalian lung. Birds combine lungs with an extensive system of air sacs - permitting a unidirectional airflow of 'fresh' air with a higher oxygen content. Mammals are saddled with bidirectional lungs that mix 'fresh' and 'stale' (carbon dioxide-laden) air.

Since birds descended from dinosaurs - they are avian dinosaurs - what does this say about dinosaurian respiration, the world in which they evolved, and more specifically the atmospheric chemistry of the planet they came to dominate?

"Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere" by Peter Ward hypothesizes that the history of atmospheric and oceanic oxygen levels throughout geologic time has profoundly impacted the nature of animal life on Earth - everything from morphology (body plans) and physiology to evolutionary history and diversity - was contingent on oxygen levels which have varied radically over time.

Ward, a paleontology professor at the University of Washington, and a NASA staff astrobiologist, is an expert in paleo-atmospheric chemistry and supports his claims with ample and compelling evidence.

Earth's atmosphere presently consists of 78% nitrogen and 21% oxygen, the final 1% composed of various gases; carbon dioxide being the most notable and problematic. 4.54 billion years ago Earth's atmosphere was a hothouse dominated by carbon dioxide. Oxygen was so scarce that Iron could not rust. Photosynthetic cyanobacteria introduced oxygen into Earth's atmosphere - precipitating an oxygen crisis - the first known mass extinction.

Since the advent of photosynthesis atmospheric oxygen levels hare varied considerably. Only 5 million years ago (MYA) oxygen levels hit 28%. The early Cambrian (544 MYA) averaged 13% and levels peaked during the Carboniferous - Permian transition (299 MYA) at 35%. By the Permian - Triassic boundary (251 MYA) oxygen levels plummeted to less than 12%.

Mass extinctions periodically reshape life on Earth. The best known, the Cretaceous - Tertiary (K-T) boundary, ended the reign of the non-avian dinosaurs approximately 65 MYA when an asteroid roughly 10 kilometers wide gouged the Chicxulub crater near the Yucatan Peninsula, setting the stage for mammals, including Homo sapiens, to become the dominant terrestrial vertebrates.

Another extinction event, the Permian - Triassic (P-Tr), some 251 MYA, is informally known as 'the Great Dying.' Up to 96 percent of all marine species and 70 percent of terrestrial species were erased as global ecosystems crumbled. Life itself nearly died as a greenhouse gas spike caused temperatures to soar 10 - 30 degrees Celsius (18 - 54 degrees Fahrenheit), and oxygen levels plummeted when the oceans became the anoxic (without-oxygen) abode of methanogenic and sulfate-reducing microorganisms - amplifying global warming (methane is 10 times more efficient than carbon dioxide at trapping heat in the atmosphere) and poisoning plant and animal life with deadly hydrogen sulfide (rotten egg gas). The sky literally turned a sickly shade of green, a topic ably covered in Ward's superb Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future.

Since dinosaurs evolved in the early Triassic - a period of suffocatingly low (to mammals) oxygen levels - any evolutionary innovations that enhanced respiratory efficiency would provide a compelling advantage. Ward contends that dinosaurs eclipsed the dominant Therapsida (mammal-like reptiles) and early mammals by evolving the unidirectional airflow lung and air sack respiratory system utilized by their avian descendents. In the Cynognathus vs. Eoraptor world of the early Triassic the race was to the swift and battle to the strong - our ancestors lost. Therapsids went extinct, early mammals retreated to niches where their respiratory and metabolic systems could cope with Triassic atmospheric conditions, and the reign of the dinosaurs began.

Along the way Ward lucidly engages a wide array of topics to make his case. The impact of continental drift (plate tectonics) and geochemistry (sulfur and carbon cycles) on oxygen levels are explored. Segmented body plans as a respiratory strategy, gills (trilobite, cephalopod, and decapod), and lungs of every variety (from alveolar to septate) are contrasted. The advent of endothermy (warm-blooded metabolism), evidence for same (turbinal bones in mammal-like reptiles and early mammals), and associated reproductive strategies (eggs vs. live birth) also illuminate Ward's insights. Circulatory advances (four-chamber hearts), even the upright posture of dinosaurs (Ward suggests the need to breathe while walking drove this innovation) are deftly dropped into a compelling evidentiary mosaic.

"Out of Thin Air" is more than a trendy title - the science shows how the dinosaurs literally emerged as a result of 'thin' air due to near-hypoxic atmospheric oxygen levels prevailing throughout the P-Tr transition. Dinosaur enthusiasts will be enthralled and mystery lovers will applaud Ward's 'science as the ultimate sleuth' approach to deciphering the history of life on Earth. Ward's Gorgon: The Monsters That Ruled the Planet Before Dinosaurs and How They Died in the Greatest Catastrophe in Earth's History makes an excellent companion volume.

Ward's book is really quite interesting to explain the "logic" of life's development on the earth, starting with the first animals (540 MA). Everything is linked to a timeline showing the rise and fall of oxygen levels over the geologic eras. It would be fatal to the book's premise, I believe, if subsequent research drastically revises this timeline.

As for criticism of Ward's writing style, there were creative forays in his writing that I most enjoyed. On a number of occasions, he takes us on an imaginary trip to visit Earth at a particular era. We are in some sort of conveyance that is boat, submarine, and plane. Like a tour guide, he explains what we are seeing -- bare rocks covered with moss and lichens, the faint haze of hydrogen sulphide in the air, the first primitive pre-phyla of the Burgess shale slowly moving across the sea bottom.

There is some repetition -- this can be criticized, but can also be helpful if one does not whiz through the book rapidly, but goes back every few days for another bite. This is not a thriller, but a rather challenging book of lay science. It is filled with mouthfilling Latinate words. A little extra help by way of some selective repetion is not that objectionable, I think.

One aspect of the book that is radically new is the analysis of the physiology of various prehistoric families of creatures. Their livers, their lungs, their feathers, their bone structure. Only in fairly recent times has this sort of discussion even been possible, and the field is sort of a "terra incognita."

Because the book covers new ground, it will remain to be seen how will the findings hold up in decades to come.

I found it intelligent, lively, and filled with new assertions and new insights. I do NOT agree with one reviewer that the book is too expensive. I got my copy from Amazon for a considerable discount from the nominal price.

Buy it if you think you will enjoy it.

Did periods of low oxygen in Earth's ocean and atmosphere - `thin air' - drive the evolution of animals? Ward meticulously correlates oxygen levels with virtually all animal species' evolutions on land and sea from the Cambrian thru-out the following half-billion years. Altho the timings of the oxygen/carbon-dioxide levels versus ancient animals' ages are both still somewhat speculative, Ward's theory seems to be the most plausible explanation I've read so far.

What caught my attention and attracted me to this book was the realization that birds migrate over the Himalayas (the book's dust-jacket and chapter headings picture Eurasian cranes in flight) while the fittest of our species struggle in the thin air to reach those heights. What enables birds to do that? Ward traces birds' respiratory system's origin to the pre-avian dinosaurs and says that at sea level birds' is a third more efficient than mammals' and at a mile high theirs is two times more efficient. However I was disappointed that he doesn't explain why birds' dinosaur ancestors survived the K-T extinction 65mya which killed off all the other dinosaurs, or how they evolved into today's birds. His focus is more on us mammals.

Some reviewers grumble that Ward's prose is flawed which impeded their reading. Granted it's a little rough but the fact that he's breaking new ground and promptly delivering the results to us, should earn him some latitude. The scope and novelty of his research is impressive, let's not quibble about its form. Perhaps his fault is that he rushed to publish his `first draft' rather than take the time to polish it, but I'm glad he did altho as I said, I think he wraps it up too hastily. (His "Under a Green Sky" was published just 5½ months later - I'll tackle it next.)

Several previous reviewers have mentioned the awkwardness of Ward's prose, so I'll simply associate myself with their comments in that regard. What for me makes this book a "must" read in comparison to Ward's other books (and most books in the field of palaeontology, for that matter) is that while it may be weak in specific parts of its technical argument, overall the pieces fit together so well that I, like a well-known cartoon character, found myself smiting my forehead and going, "D'oh! Why didn't I ever think of that?" And I've been reading palaeontology on and off for over fifty years... The major flaw to Ward's 'unified field' theory of evolutionary development is that, as one reviewer noted, it's subject to being totally unravelled if only a few of the twenty-two major hypotheses he posits in the book are disproved by later research (and some of those whose arguments he takes on in a rather combative manner are probably not happy -- palaeontologists are always not the most even-tempered group anyway). But I strongly recommend this as a good, fairly quick read that left me making lots of connections in my own mind that had never have occured to me before.

This book explains a new theory on the underlying basis for how and why animal life on Earth had the history that it did. In a word: oxygen. The one thing all animals (and plants, and fungi, and protists and most bacteria) must do is breathe - and in particular they must figure out a way to take up enough oxygen to exist. Oxygen levels have fluctuated up and down through the ages, from as high as 35% to as low as 10% (it's 20% today). Times of high oxygen means high species diversity; times of low oxygen means high diversity in body plans.

The book was written by a university professor, and although it was apparently marketed for general public reading, it really requires at least a biology degree for full understanding. I can easily see a semester-long graduate-level seminar course that uses this book as an outline. One chapter at a time, along with all the primary literature that gets cited in support of all the things each chapter says, with lots of discussion on what it all means. In fact, I suspect that the author uses this book for exactly that purpose.

As books go, this one could've used some more revising. The logic is unclear and even circular in some parts. There are places where the author starts out stating one thing, then goes off on a tangent and never gets back to supporting the original statement. And many many parts where he makes leaps, assuming that the reader knows things and can follow along if he omits stating a few in-between steps. Overall, it needs to be written from a completely different angle; as is, it looks like he's beating a tiresome drum over and over ("the answer was oxygen levels!"). It could be rewritten so that you don't start with a bunch of questions that lead to the same answer, but with the answer first followed by all the consequences thereof. It would still have the same content, but be a much smoother read.

Several factual things bothered me:

a) Early on he mentioned that birds are able to survive and thrive at much higher altitudes (thinner air, lower oxygen levels) than mammals. However, it isn't until the last hundred pages where he even mentions the setup of their lungs. That is, bird lungs have unidirectional airflow. Instead of a bag that inflates and deflates like ours, where oxygen-rich air goes in and then carbon-dioxide-laden air goes back out through the same paths, bird lungs have a system where air goes in one way and out a different way, and it's coupled to blood flow that moves in the opposite direction. It's a lot more efficient.

I spent a lot of the book wondering how he could've possibly overlooked such a basic fact, when he's writing something about oxygen and breathing. Fortunately for him, he eventually makes up for this lack by going into extreme detail on bird lungs for almost an entire chapter. Not only the details of how they're set up now (which I hadn't actually known fully), but lots of good nuggets of information from paleontology on when and from what it arose, and whether some of the dinosaurs had a setup like it (in the author's opinion: yes). But he needed to at least hint that such a section was upcoming.

b) There are whole sections in the book that strongly imply that lungs evolved from gills. No, they didn't. Lungs and gills are separate organs, and in some fish and amphibians you can even have both at the same time. Modern lungs (such as in us humans) are analogous to the modern swim bladder in bony fishes.

c) He also implies that reptiles evolved from amphibians. I'm fairly certain I read elsewhere a while back that they both came from lobefinned fish, but did not evolve from each other.

d) Near the beginning he really should've talked more about how free oxygen first came to exist on Earth. The very first life on Earth was anaerobic. Oxygen is actually a toxin and was put out as a waste product. (It's still a toxin; we're just set up to make sure it doesn't do too much damage while we're harnessing it to do useful things). Eventually the first anaerobes polluted their atmosphere with it so much that there were no more rocks left to absorb it (by oxidizing).

Also, "descendant" is the correct spelling, not "descendent."

Since other reviewers have summarized the arguments in the book quite well, I will mostly skip that here. Yes, the book is primarily about how variations in atmospheric chemistry, primarily the level of oxygen, may have affected (and effected) the evolution of life on earth. I found the fundamental premise of the book delightful and provoking, and given the fact that Dr. Ward provides a number of more-or-less testable hypotheses, I sincerely hope that grad students in paleobiology take him up, and test his hypotheses.

The biggest hypothesis in the book is the changing chemistry of the earth's atmosphere. As Dr. Ward admits early on (and it's quite hard to find the pages again to double-check this, more below), the variation in oxygen levels that form the backbone of this book do not show up directly in the fossil record, and were deduced using models, informally calibrated against fossil evidence of anoxic sediments at various time periods. Well and good, but I know just enough about such modeling to be skeptical about the concept of Model=Truth. Rather, I applaud Dr. Ward for going out on a limb and trusting the models. If and when we find a way to measure paleoatmospheric chemistry from the fossil record, this book will either prove prophetic or totally wrong-headed. As such, it is good, testable science.

What's bad about the book? Others have mentioned Dr. Ward's prose, and I have to agree. It *is* better than a majority of the scientific papers and many scientific textbooks, but as a popular science work, it needs to be lyrical and fun to read, not journal-ish. Scientific journal prose is dense because it costs so much to publish, and here, that's not an issue. There are also a number of goofs (for instance, plants have cambia, not cambria, and in a couple of places animals breath, not breathe), that make me hope for a revised and expanded edition that is more readable. I also would like to see more explanation of the illustrations that begin each chapter. They are an important summary of the material in each chapter, but they are not captioned, nor are they referred to in any consistent manner.

What's worse about the book is the lack of complete references. Yes, there's a 22 page table of references in the back of the book, but it is notably incomplete, and it is neither organized solely alphabetically nor by chapter, but by some strange hybrid system that provides the alphabetized references for some but not all topics. I could not find several papers mentioned by name in the text referenced in the back. In a book this original, I kept trying to search out where he had come up with his ideas and data, only to be stopped cold in that frustrating reference section. Paleobiology is not my field, and I do not want to spend hours tracking down papers through Web of Knowledge. In other books (notably by Jared Diamond or Charles Mann), there are exhaustive end notes and references that let me admire their scholarship. Here, someone (either the author or the editor) apparently decided that such information was unneeded in a "popular science" book. The book suffers from that decision, particularly if Dr. Ward wants people to follow in his scholarly footsteps. I can only hope that some future "revised and expanded" version of this text will properly show the breadth of Dr. Ward's scholarship and vision.

In summary, I think this is a book worth reading, and it just may provoke a revolution in the paleo-sciences. I hope it does. However, it is hampered by the clumsy writing in places and an annoying reference section. More than any book I have read, I hope to see a "revised and expanded version" come out that corrects its flaws.

For starters, the previous reviewer is incorrect about Peter D. Ward's credentials. He is a paleontologist and professor of geological science at the University of Washington.

Now then, much of the science presented in this book is new, sometimes even drawing on papers not yet published at the time of the book's publication. No doubt an entire book could be written on the evidence for varying oxygen levels in the Earth's deep past. That is not this book's place. What Ward has done is used that work as a jumping off point. If the atmosphere was only 15 percent oxygen in Cambrian times, dropping perhaps as low as 10 percent in the late Permian, what are the consequences for evolution? Did early dinosaurs get a jump on therapsids and early mammals because their respiratory systems were better suited for the somewhat oxygen-depleted atmosphere of the Triassic?

Speculative? Sure, and Ward presents his ideas as hypotheses, but well reasoned, well supported, and always fascinating.

Though countless books have been written on what killed off the dinosaurs, this book is unique in that it presents a compelling scenario on why they evolved in the first place, and an anatomical reason on why they were so successful. Not only does it discuss the evolution of the dinosaurs, it also discusses how fluctuations in the oxygen and carbon dioxyide levels in the Earth's atmosphere could have been the major factors in causing rapid evolution and mass extinctions thoughout the history of life on Earth. It is a fascinating read, in the same class as "In the Blink of an Eye: How Vision Sparked the Big Bang of Evolution" by Andrew Parker. Unfortunately, the writing is clumsy at times, and the logic is sometimes difficult to follow. And there is so much in the book that is work in progress. I expect the author to come out with a new edition in a few years with more data to support his hypothesis. And when he does, I hope he includes more illustrations of the animals he is talking about!

Peter Ward is a national resource - he is making the modern revolution in Paleontology accessible to those of us who had a LOT of plastic dinosaurs (and a few synapsids, only we didn't know that then), but failed to make a living digging.

The scope of the changes in the field is staggering and this book is letting us lay people in on the drama and excitement of the new discoveries as they happen.

The title of this book refers to the general argument that oxygen levels in the atmosphere have been very influential in the evolution of animal life on Earth over the past 600 million years. The author structures this argument quite well by providing a chronological history of life on earth over the past 600 million years. Each chapter describes a specific age or Era; such as the Triassic Era. The author shows how oxygen levels, and the fluctuations thereof, led to certain animals to become dominant at the expense of other animals. Each chapter includes one or more theses that encapsulates the author's primary arguments. Most of the chapters are also prefaced with a graph showing oxygen levels in that time period and how it compared with oxygen levels over the past 600 million years.

This book is written at a high level, and requies a good grasp of numerous branches of science, such as biology, physics, chemistry, climatology, and geology, to fully understand. One does NOT need to be an expert in science, but only to be well read. The author does a good job of presenting evidence for and against his thesis. Overall, a good book and quite insightful.