Rare Earth: Why Complex Life is Uncommon in the Universe [Paperback]

Peter D. Ward (Author), Donald Brownlee (Author)

Book Description

Publication Date: December 10, 2003 | ISBN-10: 0387952896 | ISBN-13: 978-0387952895

What determines whether complex life will arise on a planet, or even any life at all? Questions such as these are investigated in this groundbreaking book. In doing so, the authors synthesize information from astronomy, biology, and paleontology, and apply it to what we know about the rise of life on Earth and to what could possibly happen elsewhere in the universe. Everyone who has been thrilled by the recent discoveries of extrasolar planets and the indications of life on Mars and the Jovian moon Europa will be fascinated by Rare Earth, and its implications for those who look to the heavens for companionship.

Editorial Reviews

Amazon.com Review

"Do you feel lucky? Well do ya?" asked Dirty Harry. Paleontologist Peter Ward and astronomer Donald Brownlee think all of us should feel lucky. Their rare Earth hypothesis predicts that while simple, microbial life will be very widespread in the universe, complex animal or plant life will be extremely rare. Ward and Brownlee admit that "It is very difficult to do statistics with an N of 1. But in our defense, we have staked out a position rarely articulated but increasingly accepted by many astrobiologists."

Their new science

is the field of biology ratcheted up to encompass not just life on Earth but also life beyond Earth. It forces us to reconsider the life of our planet as but a single example of how life might work, rather than as the only example.

The revolution in astrobiology during the 1990s was twofold. First, scientists grew to appreciate how incredibly robust microbial life can be, found in the superheated water of deep-sea vents, pools of acid, or even within the crust of the Earth itself. The chance of finding such simple life on other bodies in our solar system has never seemed more realistic. But second, scientists have begun to appreciate how many unusual factors have cooperated to make Earth a congenial home for animal life: Jupiter's stable orbit, the presence of the Moon, plate tectonics, just the right amount of water, the right position in the right sort of galaxy. Ward and Brownlee make a convincing if depressing case for their hypothesis, undermining the principle of mediocrity (or, "Earth isn't all that special") that has ruled astronomy since Copernicus. --Mary Ellen Curtin --This text refers to an out of print or unavailable edition of this title.

From Library Journal

Renowned paleontologist Ward (Univ. of Washington), who has authored numerous books and articles, and Brownlee, a noted astronomer who has also researched extraterrestrial materials, combine their interests, research, and collaborative thoughts to present a startling new hypothesis: bacterial life forms may be in many galaxies, but complex life forms, like those that have evolved on Earth, are rare in the universe. Ward and Brownlee attribute Earth's evolutionary achievements to the following critical factors: our optimal distance from the sun, the positive effects of the moon's gravity on our climate, plate tectonics and continental drift, the right types of metals and elements, ample liquid water, maintainance of the correct amount of internal heat to keep surface temperatures within a habitable range, and a gaseous planet the size of Jupiter to shield Earth from catastrophic meteoric bombardment. Arguing that complex life is a rare event in the universe, this compelling book magnifies the significanceAand tragedyAof species extinction. Highly recommended for all public and academic libraries.AGloria Maxwell, Penn Valley Community Coll. Lib., Kansas City
Copyright 1999 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.

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Product Details

• Paperback: 372 pages
• Publisher: Copernicus (December 10, 2003)
• Language: English
• ISBN-10: 0387952896
• ISBN-13: 978-0387952895
• Product Dimensions: 6.1 x 0.8 x 9.2 inches
• Shipping Weight: 1.2 pounds (View shipping rates and policies)
• Average Customer Review: 4.0 out of 5 stars  See all reviews (137 customer reviews)
• Amazon Best Sellers Rank: #270,950 in Books (See Top 100 in Books)

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263 of 275 people found the following review helpful

4.0 out of 5 stars Still to early for final conclusions April 5, 2000

By Duwayne Anderson

Format:Hardcover

There is a long tradition among humans that we are not aloneinthe universe - that there are other worlds with other intelligentbeings such as ourselves. This tradition is found in many religions and embodied in some scientific thought. The late Carl Sagan, for example, surmised the existence of one million civilizations capable of interstellar communications in the Milky Way galaxy. Ward and Brownlee take exception to these estimates. According to the authors, microbial life is common in the universe "but even the simplest animal life is exceedingly rare." Instead of millions of such civilizations in the Milky Way galaxy there might be just a few. There might be just one.

One of the things I liked most about this book its very nice summary of the history of earth. Chapter 1 has some interesting information about recent discoveries regarding the environments in which extremophiles live. It might seem incredible to us, but extremophiles actually thrive in very high temperatures, pressures, and pH levels that we would find terribly fatal. The wide range of environments in which the simplest life forms can live gives rise to the greater probability of finding them throughout the universe. Extremophiles not only thrive in such environments, they can also tolerate brief forays into space aboard debris ejected from meteor impacts, and they can escape harsh surface conditions by living deep under ground.

The second chapter introduces us to the concept of habitable zones. For extremophiles the habitable zones are quite large, so planets harboring such life can be found in a wider range of orbits around a wider range of stars. More complex life, however, requires far smaller ranges in environmental conditions, leading to a much-reduced habitable zone. Habitable zones must also exist over sufficiently long periods of time for life to evolve. In other words, the habitable zone has both spatial and a temporal components. The upshot is that habitable zones for complex life are pretty small, and may not exist at all unless the star is quite similar to ours.

Chapter three describes some of the critical components for a habitable earth, including the creation of hydrogen and helium (and a bit of lithium) in the Big Bang, and the creation of heavier elements in stars. The earth needed to form from an inter-stellar accumulation rich in metals with the right amount of water. The authors argue that such conditions are rare in the universe, and that planets such as ours are rare as well.

Chapter four discusses the conditions on earth after the initial bombardment stopped, during the earth's early formation. This chapter has some very interesting material suggesting how bacteria, archaea, and eucarya form the earliest tree of life. Chapter 5 continues by describing how Eucarya are differentiated from the archaeans and the bacteria. Eucarya include the animals, ciliates, fungi, plants, flagellates, and microspordia that constitute the complex life that the authors claim is so rare in the universe. The key piece of evidence regarding eucarya is that they took a long time to evolve in earth's history. The message in this fact, according to the authors, is that eucarya require a more specialized environment in which to evolve - a narrower habitable zone - and that this environment must persist for long periods of time. All of which argues against this type of life being common in the universe.

Chapter 6 is called "Snowball Earth," and describes the earliest known ice ages on earth, which date to 2.4 billion and 800 to 650 million years BP. These ice ages, in contrast to the one a few tens of thousands of years ago, literally covered the entire earth and froze the oceans over. These ice ages could have helped to stimulate the evolution of animals, and (just as importantly) they also show that major environmental changes - changes that can cause mass extinction - have and can occur on earth. Timing and the extreme nature of the events are critical to the evolution of life.

The real centerpiece of this book is chapter 7, which discusses the enigma of the Cambrian explosion. Perhaps no other event in earth's history has generated as much debate and speculation as the comparatively sudden rise in complexity of animal species that accompanied the Cambrian explosion. The authors argue that the triggers for this explosion (and they offer several possible candidates) are necessary for the evolution of complex life, but they are also rare - adding further emphasis to their hypothesis that complex life in the universe is rare.

Chapter 8 describes mass extinctions and threats to animal life. Chapter 9 raises some interesting issues about the importance of plate tectonics and argues that the evolution of animal life requires plate tectonics to maintain biodiversity and to stabilize global climate. Chapter 10 discusses the importance of the moon in creating tides, contributing to orbital stability (and possibly contributing to plate tectonics) and Jupiter, which cleans the solar system of planet-crossing projectiles that could sterilize earth. Again, the point is that these conditions are rare, and so planets with complex life are also rare.

Chapter 11 describes ways in which the rare-earth hypothesis might be tested, and chapter 12 reassesses the odds of complex life in the universe via a modified form of the Drake equation. I found chapter 12 a bit of a disappointment, though, since the authors never really stick there necks out and make a claim for how many planets with complex life might exist in the galaxy. The final chapter discusses the philosophical and ethical implications of the rare-earth hypothesis, including the role people play in the current extinction crisis.

This is a first-rate book. The notes are detailed, the index complete, the text clear and understandable. The argument is lucid and in many (though not all) ways compelling. And, of course, it's hard to think of subject matter more relevant.

104 of 110 people found the following review helpful

4.0 out of 5 stars Stimulating and educational, but beware the fine print January 21, 2002

By M. A Michaud

Format:Hardcover

This is one of the most wide-ranging and readable of all science books aimed at a non-specialist audience. The authors raise Big Questions in astronomy, planetary evolution, geology, climatology, ecology, and biological evolution, reminding us of how interdisciplinary the extraterrestrial life debate really is. The vast array of subjects they address could make this book an ideal discussion text for a course designed to introduce non-scientists to scientific issues and methods. The book, at least in its hardback edition, has an uncrowded format that makes it easy to read.

Ward and Brownlee accumulate a lengthy series of arguments in support of their position that, while simple life may be relatively common, complex life is rare. At first glance, these arguments seem persuasive. However, a closer reading reveals that the authors sometimes tilt the debate in their favor by choosing the argument that best supports their case even when the evidence is very limited or ambiguous, e.g. their statement that plate tectonics "may be vanishingly rare in the Universe as a whole." How can they know this when our sample is limited to our own solar system? Sometimes, the authors make unsupported blanket generalizations, e.g. "On every planet, sooner or later, a planetary catastrophe can be expected that either seriously threatens the existence of animal life or wipes it out altogether." Stating that "it just seems to have been by chance that our Jupiter formed as it did" is hardly scientific. Oddly, after stating that SETI is a futile effort if their hypothesis is correct, the authors go on to say that "There probably are other civilizations in the galaxy that have radio telescopes." In the end, the fundamental limitation to such arguments is that they are based on the only biosphere we know -- our own. This is summed up in the authors' statement that "It appears that Earth got it just right." Life as we know it may not exhaust all the possibilities.

There are some errors. Venus does not always present the same face to the Sun. Nicholas Copernicus was Polish, not Danish. Frank Drake's equation was developed for a meeting held in 1961. One hopes that the authors will clean up these details for a second edition.

68 of 75 people found the following review helpful

5.0 out of 5 stars We Might Be All Alone April 28, 2000

By Robert Derenthal

Format:Hardcover

These two authors have written a highly informative book to support their thesis that we might well be the only multi-celled organisms in the universe. It should be stressed that Ward and Brownlee feel strongly that there are probably simple, bacteria like creatures on other planets, but nothing more complex. This is a most interesting book even if you do not agree with their hypotheses. It provides an entertaining and accessible summary of the biological, cosmological, and geological science involved in the development of our home planet. W&B feel that the necessary conditions for complex life are so numerous that few, if any, planets elsewhere could meet the requirements.

Read this book and see: 1. Why the moon and Jupiter are essential for our existence. 2. Why a system of plate tectonics is vital for the development of life forms. 3. The effects that mass extinctions have had on evolution. 4. Why life may have originated in the deep ocean near hydrothermal vents. 5. Why earth is very lucky to be located on the far edge of our galaxy.

For the scientific oriented layman this book is a true gem.