Andrew H. Knoll

Andrew Knoll’s A Brief History of Earth is the second book I’ve read so far this year that deserves to be called “popular science writing done well”.

Often after I’ve read a book that covers a very large topic - for example the entire history of planet earth from a geological perspective - I’ll be disappointed. Sometimes for the straightforward reason that the book lacks depth. Many times because it skips major events or ideas that I’m interested in, or is disjointed.

Amazingly, show more for a short book (230 pages of main text including illustrations) that covers four billion years of Earth’s history, I don’t feel that way at all after reading Knoll’s book. It packs just the right amount of information into eight distinct and easily digestible chapters. It’s a book you can read all in one sitting (like I did), or a chapter a day.

Earth Science is a pretty complicated topic because it takes ideas from chemistry, physics and biology, and blends in things like seismology, oceanography and evolution, along with ideas from other sciences. What Knoll does in this book is break that complicated topic into pieces. Each of the eight chapters focuses on a specific topic, from Chemical Earth through Physical Earth and Biological Earth and so on, up to Human Earth.

Knoll arranges the topics and chapters so that he can also use them to explain the history of our planet. The way he’s organized this book provides a natural flow. Knoll plays the part of a knowledgeable tour guide as we glide through the science and history of Earth. It's a cleverly constructed tour that packs a lot of information into an enjoyable ride.

Unfortunately, this biography is not without some drama. That comes in the latter part of the book as we near the chapter on Human Earth, where the focus is the impact of humanity on the planet.

That impact includes climate change, but also other things like a 30 percent decline in North American bird populations since 1970, as well as the massive coral mortality of Australia’s Great Barrier Reef. Human impact through fertilizer runoff has contributed to the growth of “dead zones” in the Caribbean, which have skyrocketed from 15 square miles of seabed in 1988 to over 8700 square miles by 2017.

At the end of the book Knoll offers several ideas for further reading, organized by chapter. So if any of the topics of the eight chapters particularly strikes your interest you can learn more. Helpfully, each chapter’s further readings are broken into “accessible readings” and “more technical references”.

The flyleaf overview of the book describes it as “a rigorous-yet-accessible biography of Earth”, and that’s exactly right. If that strikes you as something of interest I recommend it. It’s a Five Star ⭐⭐⭐⭐⭐ read for me. show less

Andrew H. Knoll is a paleontologist who is particularly conversant with the integrative approaches of modern day evolutionary science. Rooted in the rocks, he writes with skill about the geological and geophysical processes at work in early earth formation, and their implications for the evolution of life. He explains the complex geochemistry that became, in time, a biochemistry. He describes the so-called evo-devo (I.e., evolutionary developmental biology) revolution with verve-both as an show more observer, and a participant/contributor. He describes in some detail how the evolution of life is largely one of microbiologic changes through geologic time. Some critics fault him for leaving the good stuff for the end-a bizarre criticism given that the "good stuff" (I.e., complex multi-cellular animal life) has only been around since very recent times in geological terms. Knoll deftly defeats this prejudice by pointing out that while animals are the kings of morphological variety, it is the microorganisms that are the exemplars of metabolism. Microbes have evolved diverse mechanisms for surviving on a catastrophically evolving planet. It is in fact, the microbes that made the planet habitable for animals. This is a story as epic and heroic as any produced by evolutions most complex, and ridiculously recent, product. If I had a quibble with the book, it was with the decision to include the final chapter about the possible Martian origin of terrestrial life. Not to say this story wasn't interesting, but it would have been better left to another book. Finally, Knoll's conclusion attempts to reconcile the seemingly ever-opposed science and religion and is reminiscent of Stephen J. Gould's "twin magisteria" argument. The stronger part of his conclusion reminded us that past may be prologue: That current action or inaction may have consequences in what could be, but doesn't have to be, our own evolutionary endgame. show less

An excellent introduction to what we know about the earliest life on earth, and how we learned it. The author doesn't just tell us what is known, he gives us chapter and verse about the controversies, disputes, triumphs, and disappointments of Precambrian paleontology. The downside is that, while I found it relatively easy reading as a biologist, the book perhaps is a bit technical for lay people who may not know what the actual difference is between a protostome and a deuterostome, and show more might need a bit more explication about just what the lac operon is and why it's important. If you already have that basic knowledge at hand, the book is a pleasure to read, and the author casually drops Baby Boomer culture all throughout, which helps to increase interest (at least for a Baby Boomer who gets the more esoteric references; later generations might be scratching their heads at times and going "huh?"). The epilogue was a bit of a let down, as the author attempts to please everyone, and almost certainly winds up pleasing almost no one as he discusses the implications for religion. Other than that, a masterpiece of good writing and good science. show less

Quite an interesting book on life on Earth before the Cambrian. Being a supposed paleontologist, I am embarrassed to say I didn’t know all that much about what was going on. Like any paleontology book, there has to be a mix of geology and biology; both are well done.


The oldest hints of life are carbon isotope ratios. Not the familiar carbon-14; there’s no trace left of that. Instead it’s the ratio of the stable and abundant isotope carbon-12 to the stable but rare isotope carbon-13. show more Carbon compounds produced by biological processes tend to be enriched in carbon-12. (This is, unfortunately, a place where author Andrew Knoll does not provide a good explanation. The most facile response would be that the production of a carbon compound requires some sort of chemical reaction; molecules containing carbon-13 will be marginally heavy than molecules containing carbon-12, will move slower, and thus be less likely to react to make something else. However, that doesn’t explain why biological processes as opposed to any process results in enrichment. My guess is that synthesis of carbon compounds in living organisms requires not just a chemical reaction, but a lot of chemical reactions, and things get fractionated a little more with each step. Not sure, though). At any rate, tiny flecks of graphite in rocks around 3.5 Gya tend to be enriched in carbon-12, perhaps implying production by something alive.


By the time the Gunflint Chert was deposited – around 1.875 Gya – the oceans were teaming with life. I’ve hammered out chunks of the chert (Upper Peninsula – it’s hard – wear safety glasses), hauled them back to the lab, cut them up on a diamond saw, polished them thin, mounted them on slides, and found zillions of little filaments. The most interesting thing was a little umbrella-shaped affair (rather odd for a bacterium to have that much structure) identifiable from the literature as belonging to the genus Kakabekia. Kakabekia was known at the time (it’s since been discovered elsewhere) from two places – the Proterozoic Gunflint Chert and the latrines of Harlech Castle in Wales. Some sort of record and an indication of an ammonia-rich, reducing environment.


By 750 Mya there are definite eukaryote fossils exquisitely preserved in phosphates from the Doushantuo Formation in China. All very tiny – no more than a few cells. In the latest preCambrian – the Ediacaran – there are macrofossils. Exactly what they are fossils of is still up for debate; it’s been argued that although the Ediacara “fauna” sometimes resemble extant groups like Cnidaria, they are actually members of a whole other kingdom – the Vendobiota – with a completely different body plan from animals. The situation is confused because Ediacaran fossils almost always turn up in siltstones and sandstones – environments with enough energy to make fossilization difficult.


All this almost makes the Cambrian seem anticlimactic. I’m not doing justice here to extensive and enlightening discussions of the how of evolutionary changes from goo to us; but I recommend reading the book. Well illustrated and with good maps. show less