Oxygen: The Molecule That Made the World [Englisch] [Gebundene Ausgabe]

Nick Lane's book, Oxygen The Molecule that made the World, is a surprising volume. It mixes organic and inorganic chemistry with evolutionary studies, paleontology, research medicine, and even a little engineering to explain how the world got to be as it is. The first half of the book is dedicated to what our early atmosphere was like and how it changed as a result of biological activity. It also discusses how the evolving atmosphere, particularly the presence of oxygen, affected the complexity of early life and the sudden flourish of biological diversity after the Precambrian. The last half of the volume deals with the recent research on free radicals and their effect on health and on the phenomena of aging and of immortality.
Doctor Lane's own background is in biochemistry, and his research focus has been on oxygen free radicals and metabolic function in organ transplants. Not surprisingly he went into some detail about the free radical cascade that affects cellular metabolism and DNA integrity. I found this somewhat difficult to understand as I have only a very rudimentary grounding in organic chemistry. Still I have to admit that I know somewhat more about the process than I did before reading this book.
Probably because I know significantly more about geology and paleontology, I enjoyed more fully the author's synthesis and analysis of what we know of the geological and biological development of our atmosphere and our planet. Some of this material was familiar to me from other sources: Certainly that O2 can actually be a "poison" I know from managing patients with ARDS (adult respiratory distress syndrome) on mechanical ventilators with 100% O2; that the earth went through a series of green house earth/snowball earth phases early in its history I had learned from Ward and Brownlee's book Rare Earth; that life had begun almost as early as it was able and much earlier than had been previously believed, I was aware of from works by Gould, Schopf, and others; and that the mitochondria may once have been free-living, aerobic organisms that formed a symbiotic relationship with anaerobic organisms was known to me from my past exposure to microbiology in a nursing class.
New to me however, was the concept that gigantism may have been a means of limiting the negative effects of a periodic increase in oxygen in the environment, as Dr. Lane suggests in his chapter on The Bolsover Dragonfly. Although I had read an article that suggested that the immense sizes achieved by some of the dinosaur species might have been due to a higher percent of O2 at the time, I had also understood that it was because oxygen was a "good" thing, an opportunity of sorts. Lane points out that the negative effects of oxygen on tissues and DNA through the free radical cascade might have been ameliorated by an increased size. An animal--or one presumes also a plant--that increased its size might have been able to distribute negative effects over a greater body mass. One wonders if the rise of the mammalian mega fauna of the ice ages and their sudden almost catastrophic disappearance might not also have been due to some temporary fluxuation in the oxygen level of their atmosphere. (In which case the early Native Americans could be once and for all exonerated of having liquidated them, since their demise would have been dictated by a return to a baseline oxygen level!) If this were the case, one might also question what type of changes might be expected among our own kind as a result of such an increase and decrease of atmospheric oxygen.
I found the doctor's ideas on the trade off between sexual reproduction and immortality a unique approach to the topic of aging. Some of this information--the studies of animal reproduction rates, predation, and age at death, for instance--was known to me. Dr. Lane's discussion brought it together in a much more complete way.
Certainly the concept of sexual reproduction being one of life's mechanisms of perpetuating the fragile, complex organic molecules (DNA) in an oxidative environment was interesting. I had read Ridley's proposal that sexual reproduction evolved as a means of resisting bacterial infection, but Lane's suggests why it began as early as the DNA swapping behavior among early single eukaryotic cells. That the massive increase in biological diversity was an indirect product of the release of oxygen into the atmosphere, is truly an amazing thought. In the event as Lane makes claim in his subtitle, oxygen was truly "The Molecule that made the World."

In school, we learned of the ubiquity of hydrogen in the universe. It made up the stars, drifted between the galaxies, and, combined with nitrogen, composed the atmosphere of our solar system's giant planets, Jupiter and Saturn. We learned, too, how it combined with oxygen to make our planet's blessing - water. Oxygen was deemed the life-giver, earning our respect even when we burned things with it in the lab. That "burning" is a key element in Lane's treatise. We're all aware that without oxygen, we cannot live. On the other hand, too much of this vital element attacks our cells and contributes to the ageing process. Consequently, we've turned to "anti-oxidants" in hope of diminishing the negative aspects. Lane issues a strong cautionary note about this practice, using a strong evolutionary base to build his case.

Science has long known that the early Earth had little free oxygen in the atmosphere. The famous Urey-Miller experiments used a "reducing" atmospheric environment to build their compounds. Traditional biology argues that oxygen was emitted by photosynthetic bacteria as a waste product. Existing life thus had to adapt to this poisonous atmosphere. Lane challenges this view, describing mechanisms that made early organisms already oxygen tolerant. He contends that the Last Universal Common Ancestor, a minute organism residing in shallow seas, learned to break water into its component gases, using freed energy. In striking a balance between using oxygen as an energy source and preventing that energy from consuming the cell, life developed finely honed processes. Oxygen is more than just used by life, it is constrained and controlled carefully in organic mechanisms. As life gained in complexity it used oxygen to improve those control processes. We tamper with them at our peril.

The key is in how life deals with "free radicals". These compounds steal electrons, which are the basis for life's functioning. Free radicals have had some bad press in recent years, as Lane reminds us. There is much available advice about dealing with them and a pharmacoepia of "medicines" to be had that claim to reduce them or their impact. Lane argues that the complexity of processes and varying conditions within the body make any claims to deal with them highly suspect. The bottom line is that we don't have nearly enough knowledge about how the body copes with free radicals to have confidence in any of the suggested therapies.

Nearly a quarter of this book focusses on a question confronting us all - ageing. There have been countless attempts to understand the ageing process, most with the ambition to thwart or delay it. Their success rate has been notably abysmal, notes Lane. Approaches range from "oxygen pubs" to heavy doses of vitamin C. The author points out that not only is the concentration of oxygen used by each cell miniscule compared to what's available in the atmosphere, the processing system is many levels removed from the source. The body will use what's needed and scorn the rest. Flooding the body with oxygen or vitamins is more likely to impose "oxygen stress" than deliver any real benefit.

Lane's thorough analysis makes this book anything but a quick read. He follows evolutionary paths, historical accounts of research in all aspects of life, and explains organic processes in minute detail. He presents a complicated and long-term story, but his explanations are rendered with clarity and precision. It is simple to condemn this book for its wealth of information. That's the reaction of one seeking simple answers. It's easier to praise this book for its sweep of both history, precise evolutionary biology and breadth of information on a topic critical to our existence. With an extensive glossary and strong list of reference material, it's a boon to those wishing to understand our world and life's foundations.

[stephen a. haines - Ottawa, Canada]

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.