For a relatively short book, Lane's story about oxygen covers an amazing scope that cuts across huge swaths of science including geology, paleontology, anthropology, biology, geo-physics, evolution, and medicine. Although Oxygen is fascinating for the story it tells of earth's evolution, it's also contemporary in the way it deals with one of the oldest questions faced by humankind - how and why we age and die.
Most people know that the oxygen in our atmosphere comes from plants, and that we need oxygen to live. Recent science news has also spread the word that oxygen has a darker side because it causes cell damage and oxidative stress. Purveyors of health foods explain the value of things like green tea in terms of their anti-oxidants and their supposed ability to neutralize the harsh effects of oxygen on human bodies. But there's a mystery here; if oxygen is so toxic, why did so many life forms evolve to depend on it? Though an apparent mystery, this subject is the topic of intense research which is beginning to explain this particular tale of evolution.
This is one of the better books I've read in the last year. For the most part it is relatively easy to read, though there are times when the book is hard to follow. For me, some passages required reading over and over again before I could confidently say that I understood what the author was saying. In a few cases, though, I was never clear and finally had to simply guess.
Whenever I checked the books accuracy I found it to be generally correct, though there are a few places that stumped me. For example, on page 65 Lane says:
When ionized, a single atom of organic carbon gives up as many as four electrons to form carbon dioxide. A single atom of organic carbon therefore consumes four times as much oxygen from the air as does a single atom of iron.
This looks like a mistake. Carbon dioxide, of course, consists of a single atom of carbon and two of oxygen. Iron (III) oxide (also called ferric oxide, red iron oxide, synthetic maghemite, rouge,or rust) has chemical formula Fe2O3. Based on these chemical formulas, a single atom of carbon consumes 2 atoms of oxygen while 2 atoms of iron consume 3 atoms of oxygen. Thus a single atom of carbon consumes 1.33 times as much oxygen as a single atom of iron; not 4. In the case of magnetite, Fe3O4, the ratio is 1.5:1.
According to Lane, "ageing and age-related diseases are degenerative conditions brought about by the combination of mitochondrial leakage, oxidative stress and chronic inflammation." [Page 310]. This position is likely to be non-controversial (or only slightly controversial) with other researchers. That being the case, how did life (or, at least the macroscopic animal life that we are mostly familiar with) come to be so dependent on oxygen in the first place?
The author argues that life was exposed to oxidative stress long before there was any free molecular oxygen in the atmosphere. Because there was no free oxygen in the atmosphere, there was also no ozone, and the lack of ozone meant high UV radiance at earth's surface. This ultraviolet radiation split water molecules to produce hydroxyl radicals, super oxide radicals and hydrogen peroxide.
According to Lane, the earliest life on earth adapted to the environment at the ocean's surface, and evolved antioxidant enzymes for protection against the radiation-produced reactive oxygen intermediates. He supports this conclusion with a great deal of scientific data, including genetic studies that suggest the latest common ancestor to all life on earth had antioxidant enzymes, including SOD, catalase, and peroxiredoxins.
According to the story told by Oxygen, shortly after the early meteorite bombardment that created the moon and earth, 3.85 billion years ago, life had evolved the ability to generate energy from oxygen respiration and was already resistant to oxidative stress, even though no free oxygen had yet accumulated in the atmosphere. Later, as photosynthetic cyanobacteria evolved, they spewed oxygen into the air. This prevented additional radiative dissociation, and loss, of the water in earth's oceans. Venus, in contrast, lost it's oceans through a runaway greenhouse effect.
Midway through the book Lane takes what appears to be a side trip into the (apparently) unrelated topic of radiation poisoning. This chapter is very interesting in its own right, but I thought the author had forgotten the title of his book. Imagine my surprise when Lane tied it all together by explaining how the damage caused by radiation is chemically the same as that caused by oxidation. It was one of the more innovative twists and reconnects I've seen in a science book.
The scope of subjects touched by Lane's book is impressive. In addition to nicely telling earth's geological and biological history, the book also includes such interesting discussions/explanations as the origin of sex and aging, and how oxygen played a role in each case. Throughout the book there are mini tutorials. One such tutorial describes untangling the history of evolution by looking at variations in the genetic code, and how such techniques are becoming more sophisticated and accurate, and subsequently used as powerful tools in unraveling the history of life on earth. Another tutorial briefly covers the science of using the ratios of different isotopes of carbon to estimate the amount of biological activity during the earth's past.
In telling the story of oxygen, Lane has crafted a masterpiece that takes the reader on a journey of discovery, touching far-ranging subjects and leaving a pleasing sense of world view that ties together seemingly disparate subjects into an unanticipated whole. I highly recommend this book.