Life on a Young Planet

The author of “Endless Forms Most Beautiful” cited Life on a Young Planet as a source, and one of his favorite science books.
Harvard paleontologist Andrew Knoll weaves together geology and paleontology to tell the story of life before the Cambrian Explosion. “Life on a Young Planet” explores scientific mysteries that don’t yet have clear answers.
In the Proterozoic age, 600 to 800 million years ago, there are clear signs of life, with bacteria and algae with colonial living patterns similar to their descendents in tidal flats today. Rewind to 3.5 billion years ago, and there are much more cryptic signs of life that can’t be conclusively distinguished from non-living processes.
Fast forward to 540 million years ago, at the end of the Proterozoic era, and there is a profusion of Vendobiont animal forms, strange and unlike the predecessors of recognizable organisms that proliferated during the “Cambrian Explosion.” Scientists still don’t know how or whether these alien creatures are related to the generations that followed.
One of my favorite sub-plots of the book is the story of the co-evolution of life and the planet. Early in earth’s history, oxygen was scarce. Early bacteria metabolized methane, sulfates, and other chemicals. The proliferation of cyanobacteria helped create the oxygen-rich atmosphere that allowed large and complicated life forms to flourish. Here, also, scientists still have unanswered questions about how the earth’s atmosphere evolved.
The book is clearly written, without condescension or the purple prose that affects some scientists freed of the constraints of journal articles. One of the strengths of the book is the way Knoll explains how scientists figure out what they know — the dating methods, chemical analysis, comparisons with modern life forms, geological mapping, and other techniques used to piece together the stories of ancient life.
I really enjoyed this book — it left me with a sense of awe about how much scientists have learned about the evolution of life, and how much is still unknown.

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