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Born of Ice and Fire: How Glaciers and Volcanoes (with a Pinch of Salt) Drove Animal Evolution
An exploration of how the Cryogenian Period, when our planet was covered in ice for millions of years, created today’s remarkable biodiversity
More than half a billion years ago, our world was completely covered by glaciers, a “Snowball Earth” that persisted for millions of years. Incredibly, this unimaginable cold led to the remarkable diversification of life on earth known as the Cambrian explosion. With a geologist’s eye and a knack for storytelling, Graham Shields explores when and how such inhospitable conditions enabled animals to evolve, radiate, and diversify into our earliest ancestors.
This journey navigates the wild swings between hot and cold climates, oxygenation and asphyxiation, biological radiations and extinctions, asking how such instability relates to grander forces that brought our planet to its modern state. Shields guides readers through evidence found in the Australian outback, Mongolia, Scotland, and other locales, revealing how geologists can trace glaciation, the atmosphere, oceans, mountain building, and more through the earth’s rocks, providing a comprehensive theory of how life evolved and diversified.
More than half a billion years ago, our world was completely covered by glaciers, a “Snowball Earth” that persisted for millions of years. Incredibly, this unimaginable cold led to the remarkable diversification of life on earth known as the Cambrian explosion. With a geologist’s eye and a knack for storytelling, Graham Shields explores when and how such inhospitable conditions enabled animals to evolve, radiate, and diversify into our earliest ancestors.
This journey navigates the wild swings between hot and cold climates, oxygenation and asphyxiation, biological radiations and extinctions, asking how such instability relates to grander forces that brought our planet to its modern state. Shields guides readers through evidence found in the Australian outback, Mongolia, Scotland, and other locales, revealing how geologists can trace glaciation, the atmosphere, oceans, mountain building, and more through the earth’s rocks, providing a comprehensive theory of how life evolved and diversified.
352 pages, Hardcover
Published October 17, 2023
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Displaying 1 - 2 of 2 reviews
October 31, 2024
This is a tough read for anyone who is not a geochemist specializing in the past! The author throws a LOT at you, and not especially well-structured for the novice.
Even so, it's worth reading simply because it opens your eyes to so many background concepts rattling around in this space that I thought were either settled, not worth worrying about, or considered speculative. In that sense, it's like Donald Prothero's skepticism regarding the importance of a meteorite vs volcanic activity at the KT boundary -- it reminds you yet again that just because a certain story is especially easy or dramatic for the mainstream culture to understand, doesn't mean it's true, or even settled.
The main elements I took from the book (all of which I hope will become more obvious as I read more very recent geology and look for links) include
- the Wilson cycle (continents coming together to form a supercontinent, then splitting apart) is not only considered non-speculative, but cycles have been traced back through at least five supercontinents. My recollection is that in the 80s and 90s even talk of Rodinia (supercontinent before Pangea) was considered fanciful and speculative.
- ultimately tectonics drives everything. People like to talk of nutrient cycles (eg carbon or phosphorous cycles) as driven by life, but these cycles existed before life, in very different forms, and when they change (generally because of tectonics) it's life that adapts (after a great die-off), rather than life rapidly compensating for the consequences of the new geology
- previous geochemistry was very different from that of today, and in multiple different stages of different
- sulphur has had a substantially more important impact on the world (as a sink, and then source of oxygen, via sulphates) than was realized until recently
If any of this interests you, stick with it. And hope that someone with the explanatory skills of, say a Nick Lane, gets interested in this area and writes a successor book!
Even so, it's worth reading simply because it opens your eyes to so many background concepts rattling around in this space that I thought were either settled, not worth worrying about, or considered speculative. In that sense, it's like Donald Prothero's skepticism regarding the importance of a meteorite vs volcanic activity at the KT boundary -- it reminds you yet again that just because a certain story is especially easy or dramatic for the mainstream culture to understand, doesn't mean it's true, or even settled.
The main elements I took from the book (all of which I hope will become more obvious as I read more very recent geology and look for links) include
- the Wilson cycle (continents coming together to form a supercontinent, then splitting apart) is not only considered non-speculative, but cycles have been traced back through at least five supercontinents. My recollection is that in the 80s and 90s even talk of Rodinia (supercontinent before Pangea) was considered fanciful and speculative.
- ultimately tectonics drives everything. People like to talk of nutrient cycles (eg carbon or phosphorous cycles) as driven by life, but these cycles existed before life, in very different forms, and when they change (generally because of tectonics) it's life that adapts (after a great die-off), rather than life rapidly compensating for the consequences of the new geology
- previous geochemistry was very different from that of today, and in multiple different stages of different
- sulphur has had a substantially more important impact on the world (as a sink, and then source of oxygen, via sulphates) than was realized until recently
If any of this interests you, stick with it. And hope that someone with the explanatory skills of, say a Nick Lane, gets interested in this area and writes a successor book!
August 24, 2024
Personal and intellectual review written by the author’s son, Oliver Shields, “What Geologists and Political Scientists Can Learn From One Another” (title inspired by famous political scientist Harold D. Lasswell): https://totalrevision.blogspot.com/20...
Displaying 1 - 2 of 2 reviews