The likelihood of complex life on other planets in the universe is the topic of my book for review this month. Don't be alarmed, you have not jumped into a review of an upcoming X-Files show. No, you remain firmly in the solid grasp of reality. This is a book for enthusiasts of paleontology although at first glance it may not seem to be so.
Rare Earth, Why Complex Life is Uncommon in the Universe is the book to be reviewed. One of my favorite authors, Peter D. Ward, wrote Rare Earth along with Donald Brownlee. Ward is a Professor of Geology and Brownlee is Professor of Astronomy, both at the University of Washington in Seattle. I have favorably reviewed a number of Ward's books in this column. Brownlee specializes in the study of the origins of the solar system and astrobiology. Rare Earth is a 333 page work published by Copernicus in 2000. The book retails for $25.00 in hardcover.
Let me explain the connection between the existence of complex extraterrestrial life and paleontology. It is always hard to estimate such things but I would suggest that over half of this book deals with paleontology and earth geology with extensive treatments of the origin of life on earth, evolutionary jumps, and mass extinctions. Smoothly blended with the paleontology, are illuminating descriptions of the formation of stars, planets, our solar system, and the geologic processes of the earth that make life possible.
Rare Earth has melded the knowledge of the two author's specialties to present a cogent and compelling case against the likelihood of complex life in the vastness of the universe. Ward and Brownlee explain in their prefatory comments that their proposal is contrary to that held by most other scientists working in this field, the most famous perhaps being the late Carl Sagan. Before I go further, I want to be certain that you understand the perhaps subtle difference between complex extraterrestrial life and that of simple extraterrestrial life. This is an important distinction. Simple life forms would include animals like bacteria and viruses. Complex life on the other hand includes animals and plants.
Through the course of building their case, Ward and Brownlee show that the earth itself is a very special and rare body in itself. Since Rare Earth unites astronomy, geology, and biology so seamlessly, the reader easily follows the explanations of the relatedness of stellar, geologic, and biologic processes from the origin of the universe through evolution of complex life on earth. I personally found this enlightening. Here are but a few examples:
The fact that all of these conditions exist and have since the formation of the earth has provided this planet with a great deal of stability of over 4 billion years. Long term stability is the key here. Complex life requires a functioning evolutionary process that in itself takes millions of years. Without this stability no complex life can evolve. In the briefest of terms, these explanations of fact support the concept that the earth is an extremely special planet. The probability that another such planet exists in the universe becomes statistically insignificant.
As in any good scientific work, the hypothesis must be subjected to tests. Ward and Brownlee suggest a few such tests. One of the tests is the spectral analysis of the atmosphere on potential life harboring planets that would detect water, carbon dioxide, and ozone. As pointed out in Rare Earth our atmosphere of nitrogen, oxygen, and water vapor is highly unstable. Without the life processes, these elements would combine naturally to form nitric acid and make the oceans slightly acidic.
Many of the traditional sciences began using interdisciplinary approaches in research more frequently in the last part of the 20th century. The investigation into the famous impact hypothesis surrounding the extinction of the dinosaurs is a prominent example. This book is another good example that can give readers a bigger picture of just how everything fits together. In addition, Ward and Brownlee have illustrated rational thinking and application of the scientific method while building their hypothesis. Rare Earth is one of those books that I urge you to seek out.