The key question in astrobiology is whether we are likely to find life beyond Earth, and the authors of this book, who are clearly optimistic about the answer, put forward strong arguments to support their optimism. Whether you agree with them or not, this book will help you think critically about the possibility of life beyond Earth, and about the likelihood of complex life being common in the universe, in direct contrast to the Rare Earth hypothesis. It will also remind you of how astonishing wonderful life on our planet is.
The authors, Schulze-Makuch and Bains, are scientists well-versed in microbiology, the chemistry and the evolution of life. They start from the premise that if abiogenesis is not particularly rare, simple life will appear in other worlds as long as the conditions are right, and that complex life will evolve as long as the environment remains habitable for long enough. From here, they explore at length the different bottlenecks that life on Earth had to go through in order to make the jump from simple to complex life, and from complex life to intelligent and technologically advanced societies. They provide an extensive yet concise account of how life appears to have evolved on Earth, and how different evolutionary pressures resulted in increasing complexity of anatomy, physiology and behaviour. For each key evolutionary step described, they ensure that the reader is aware of the difficulties life had to overcome in order to make it through a particular evolutionary barrier. However, they make a clear distinction between processes that appear to be oddities and unlikely to happen again, and processes that appear to be common and that have occurred many times but in different ways. The authors’ focus is on how likely it is that key evolutionary innovations will happen, even if the path taken to get there is different from the one observed on the Earth.
If life is common in other worlds, and there are many ways for life to evolve into complex organisms, then it is likely that we are living in a cosmic zoo. However, as the authors point out towards the end of the book, this is just a hypothesis, and one that cannot yet be tested. Hopefully, the increasing pace of technological progress and our continuous exploration of the Solar System will allow us to find some answers in the not too distant future.
My only minor criticism about this book is that I expected more discussion about habitability and the extreme conditions under which life survives on Earth, how this informs our search for life beyond Earth, and our expectations of finding it.
I would highly recommended The Cosmic Zoo to any undergraduate and postgraduate student of Planetary Sciences and astrobiology; the further reading lists provided at the end of each chapter are an added bonus. Because the book is written in a jargon-free manner and has a helpful glossary at the back, it is also a great read for anybody with an interest in astrobiology, SETI, and the evolution of life on Earth.
Reviewed by: Marina Barcenilla, University of Westminster
