Oxygen: A Four Billion Year History

The history of oxygen is more complicated than I expected. I liked the way the author tied together different evidence: physical (fossils where possible and ratios of isotopes where not) and the evolution of DNA. I liked how when there is a difference of opinion he gave us the range.

- like it or not this book gets technical, you should have some high school sience to get it - but you won't have to brush up on it either. For teachers, scientists or students this is the story of the origin and life on earth from a geochemists perspective, a wiew that can be stunning. Canfield is a leading figure in his field, and how refreshing it is to see those guys just say what they think outside the wrappings of academic language and provisions! The text is not completely unraveled from academic wrighting and the kindle formatting obscures my understanding. to me the book is at its best when you are given a little recess as Canfield wonders of topic, before he continues his sometimes difficult lecture. I did require more respites than he provided, but that's easy; it's a book. The lecture is well worth following!!

a comprehensive overview of current research on the biogeochemistry of oxygen

When people think of oxygen, if they think of it at all, it is that it is produced by plants and is necessary for most life on earth. There really is never any thought to how the concentration of oxygen stays at about 21% (at sea level) or where oxygen comes from. It's just there, and nothing I ever had in biology gave any other answers…it was always the "respiration loop" of carbon dioxide being absorbed by trees and oxygen produced which is then breathed in by animals which creates carbon dioxide and around we go. So, it was a surprise to discover there was so much more to the oxygen story and that oxygen wasn't even present on the planet when it first began. The writer writes well for a scientist, which is no small feat, however this book is not really for the everyday reader. I was a biology major in college (oh so many years ago) and had the mandatory amount of chemistry, but absolutely no geology. And, to fully appreciate the story the author is telling, you need a working knowledge of both of these subjects. The writing was clear…it was the subject matter that made the reading extremely difficult. Even with the above caveat, I enjoyed the book. It took me a while and I had to reread a number of sections before I got it, but I eventually did get through it and found it to be fascinating. My warning is not to get this thinking it is a popular science book…it is real science and it can be very dense reading.

I enjoyed reading this book. I was quite surprised that scientists have been able to delve so far into the past, beyond the usual visible fossils to some 2.5 to 4 billion years ago when no structural evidence of fossils exists. The "chemical footprint" of early bacterial organisms shows up in isotopic shifts for elements such as carbon and sulfur, or in the absence of oxides of iron or manganese indicating anoxic conditions. Possible evolutionary pathways from preoxygenic photosynthesis to the first oxygenic photosynthesis as exhibited by the cyanobacteria are sketched briefly. It's quite fascinating how the chemical/isotopic fossil record points toward a reasonable estimate for when significant levels of oxygen appeared on the scene, referred to a a series of oxygen whiffs followed by the Great Oxidation Event. The subsequent history of atmospheric oxygen buildup, leading to more complex organisms starting to show up in the structural fossil record (Ediacaran fossils), followed later by very high atmospheric oxygen levels (estimated at around 35%) in the Paleozoic Era, resulting in the formation of the huge coal deposits we see today (natural carbon sequestration coupled with oxygen buildup). The estimated high oxygen levels of the Paleozoic Era serve to explain how giant insects could evolve (high O2 in air allows for adequate transfer and diffusion of O2 into the tissues - a capability that limits modern insects to the smaller size they have today. It's a fascinating journey into Earth's early past and explains a lot that I never realized. The author discusses his interactions with other scientists and how theories are put forward and tested. He also gives his account a personal touch, recounting his social contacts and cooperation with scientists around the world. Scientists form a very special community and great science comes with open-mindedness balanced with a healthy skepticism over new theories, even one's own. True science puts theories to the test of what we see in the evidence. The book tries to keep chemical and biochemical mechanisms to a very simplified minimum. I actually got a little confused because I would have liked to see the full equations for the chemical reactions so I could see how it all fits together. However, the author is writing to a broader public and obviously needs to popularize the account and not bog readers down with too many details of chemistry. Otherwise, the book would fail to reach a wider audience. It is amazing what scientists have learned about the early evolution of life on Earth. If you are interested in learning about this area of our knowledge of our planet, then I strongly recommend this book to you.