Ward, Peter, Out of Thin Air: Dinosaurs, Birds, And Earth’s Ancient Atmosphere, John Henry Press, 2006. 282 pp.
Out of Thin Air takes the reader on a wide-ranging journey through the earth sciences, melding cosmology, the geological and climatological history of Earth, and the story of the evolution of life on Earth. It’s a unique reading experience because it proposes a theoretical change-of-perspective so profound and so recent that the author is hustling (with a large number of scientific colleagues) to publish scientific articles which outline the implications of the new information and re-assess many assumptions about the ancient past. Out of Thin Air is a snapshot of science on the run. What it lacks in conclusiveness it restores with the excitement of iconoclasm and the possible revision of decades-old assumptions.
The book opens with the haunting image of mountain climbers dying of hypoxia near the top of Mount Everest as Tibetan bar-headed geese migrate overhead without apparent danger. How are birds able to survive flight at such high altitudes during such tremendous migratory exertions? Clearly, bird physiology is different in some profound way from that of mammals and reptiles. What are the ancient roots of this difference and does it have anything to do with the apparent dinosaurian origins of modern birds?
The fundamental premise of the book is that oxygen levels have varied dramatically on the surface of the Earth since the appearance of “animals” some 600 million years ago. Since oxygen is central to the metabolism of all animals, oxygen levels place severe limits on which species can live where … in the sea, on land, at elevation. An increase of oxygen in the atmosphere gives latitude for life to proliferate at higher elevations, at greater size, and for more ancient (and less efficient) forms of respiration to extend slowly into new geographies, and evolve in efficiency. A collapse in oxygen levels, however, decimates ecosystems and pushes animals back into safer and more constrained locations.
Since the story of life is in many ways a tale of increasing adaptation to new environments, the oscillations of oxygen in Earth’s atmosphere have had dramatic selective effects on animals from the most humble to the most famous, such as the dinosaurs and mammals. According to the author, then, the amazing respiratory system of the bar-headed goose is inherited from a very ancient dinosaur system, and adapted for a time when oxygen levels (even at sea level) were a fraction of what they currently are. Dinosaurs outlasted their mammal-like reptilian neighbours for the simple reason that they could breathe more effectively, move more rapidly, and reproduce more successfully in low oxygen atmospheres.
Since this new perspective on Earth’s atmosphere is all but unknown to the authors of books on the evolution of life written more than five years ago, Ward’s writing has implications for the pet scientific theories of hundreds of scientists. Because respiration is central to metabolism and metabolism is central to so much else (including reproduction), the idea that oxygen levels were constraining or enhancing the evolution of life has a ripple-through effect on the biggest controversies regarding: animal speciation, the appearance of animal life on land (with one apparent major false start), the giant insects and undecayed buried forests of the Carboniferous period, the evolution of eggs and warm-bloodedness, the distribution of dinosaur fossils, and the dramatic (and wildly popular) question of animal extinctions.
In fact, Ward’s hypotheses now place a new emphasis on research into modern insect and bird physiology. Early investigations suggest that insects can be bred much larger in high-oxygen lab settings … and the first comprehensive examination of avian breathing has only recently been completed. Ward cites whatever supporting research is available but clearly if his insights into palaeontological events hold up, there will be a wave of new research initiatives in biology labs around the world seeking to confirm the physiological relicts of ancient times in the bodies of modern animals. Perhaps dragonflies with 18-inch wingspans will yet reappear on the planet.
Out of Thin Air is suitable reading for a college student or someone with a basic background in the life sciences. It would be rather challenging for high school students but might just re-inspire a budding palaeontologist who’s finding high school chemistry and biology a burden rather than a joy. Occasional mangled syntax and spelling mistakes are the hallmark of modern copy-editing but in general the author does a very good job of communicating the history of life, the chemistry of Earth’s atmosphere and oceans, and how varying oxygen levels affects animal physiology and behaviour.
What was Earth like during different periods of geological time? What was the air like? The sky and sea? The plant life and the animal life? The nature of streams and rivers? Each of these elements, in its own way, is an indirect indicator of earth’s environment and its life forms. Through small “you are there” vignettes, the author successfully introduces us to an Earth which is quite foreign.
This is an Earth where trees and grass made a late appearance. A giant single continent (Pangaea) might have been largely uninhabited by animals because the uplands were too “high and dry” (altitudinal ecozone compression). And the oceans themselves might at some points have turned purple with algae releasing toxic hydrogen sulphide in vast clouds. Life might have clung to a ribbon of seashores — a ring of isolated populations rather than undifferentiated continental mass of interbreeding life. It’s a planet where air-breathing reptiles returned to the oceans (e.g. icthyosaurs) as a response perhaps to respiratory stress, and where the first attempts to colonize the land were largely unsuccessful.
As someone with a general interest in the past (though I haven’t followed the intricacies of palaeontological debate in the last few decades), my interest in this book was sparked by a podcast interview with the author on CBC Radio’s Quirks and Quarks science program. His explanations were so lucid and enthusiastic that tracking down the book seemed mandatory. This dramatic re-interpretation of the past is supported by a new understanding of earth history and new techniques for dating and modeling events. Scientists now have an ever-expanding range of supporting information with which to test whether extinctions were tied to celestial, terrestrial or oceanic events. No doubt we’ll see new re-interpretations of life’s story as more research continues. The latest tremor in the global warming orthodoxy, for example, comes “out of the blue” from a cosmic ray hypothesis which has struggled for funding and acknowledgement in the face of a contrary political headwind. Perhaps another 20 years of science will give us more skepticism about our ability to “fix things” on this planet, and our vulnerability to processes that are far beyond our capacity to fine-tune.
It’s not extreme to describe the impact of Ward’s approach as revolutionary — upsetting the chain of argument for many palaeontological events by adding a dramatic new variable to the forces of natural selection. It’s not entirely clear in this work for general readers, which hypotheses will hold up and which will be cast aside promptly. Science proceeds, as one wag put it, one funeral at a time. If so, the full impact of ancient atmospheric modeling and of the issue of oxygen variability may await decades of further research. In coming years, we’ll get a chance to see whether Ward’s oxygen-level model has as much significance for the story of animal life as he currently proposes.
In the meantime, we have a book well worth reading. It’s highly recommended for those with an interest in the natural sciences. And it would be an ideal birthday gift for a college-age science student or someone with an amateur’s interest in palaeontology. It can be a challenging read occasionally, if only because of the focus it demands in following the arguments from atmospheric chemistry, anatomy, and evolutionary biology. But the necessary effort is modest, the scientific background required is quite basic, and the results are quite rewarding and inspiring. Out of Thin Air reveals just how much more we have to learn about such distant and unimaginably long time-frames.