Against all odds?

RARE EARTH: Why Complex Life is Uncommon in the Universe
By Peter D. Ward and Donald Brownlee
Copernicus
Hardcover, 333 pages

RARE EARTH attacks one of my most cherished notions, that life exists beyond Earth. I've been holding out for the discovery, not of just life, but of abundant life, of intelligent life, of technological civilizations elsewhere in the universe. I've been waiting since I read Walter Sullivan's We are Not Alone as a precocious kid in the '60's. My favorite tee shirt is the one my son decorated with the Drake Equation. My PC helps researchers to process SETI data from the Arecibo radio telescope. However, this book is a wake-up call for SETI researchers, their devotees, and detractors.

With the benefit of nearly forty years of astronomical research behind us, we should admire the bold assumptions originally made by radio astronomy pioneer Frank Drake in 1961, when he came up with a formula for estimating the number of probable communicating planets in the Milky Way Galaxy. Though his was not a bad rationale, considering Drake was flying blind, it is time to reevaluate the probability of intercepting signal from ET.

Today the number of confirmed extrasolar planets is edging past the two dozen mark, yet we have not identified another star system, much less a planet, that remotely resembles our own. Of course this is a minute and not a representative sampling of the entire galaxy. However, even as the body of evidence grows to support the assumption that most stars do evolve planetary systems, we are discovering that our own system is not the norm, but a highly atypical case.

Earth happened to form around a fairly stable star, away from busy, dangerous galaxy central. It coalesced with a felicitous complement of heavy elements and ended up within the Sun's habitable zone (as did Venus and Mars). Earth's present axial tilt moderates the amount of solar energy received over the planet's surface. It wound up with a huge moon, relative to its size, which nicely moderates the planet's spin. All in all, Earth has been rolling sevens in the big, cosmic crap-shoot.

RARE EARTH's authors, Peter Ward and Walter Brownlee, both University of Washington scientists, begin by making an excellent case for extraterrestrial life, and lots of it. They reprise the discoveries of microbes surviving inside rocks, near ocean floor thermal vents, in boiling water on Earth. They feel that these tough creatures may certainly have counterparts in Martian rocks, Europa's ocean, in the atmospheres are giant gas planets, and in environments we can't yet imagine.

We have evidence that simple microbes spread about an geologically unstable, oxygen bereft, infant Earth, 4 billion years ago, an astonishingly short time from the planet's beginning. And the speed continued, going from promordial "… soup to bugs in ten million years," as Ward and Brownlee put it. However, it took another 3 billion years for animal life to evolve. It is from this point the authors raise the book's core argument which is the improbability that complex, multi-cellular organisms, commonly arise, survive and evolve in a hostile universe.

Mother Earth herself could not support animal life until very recently on the geological time scale. The history of complex life is fraught with starts and stops, and periodic mass extinctions. Science is still puzzling over many mysteries crucial to our understanding: Why did multi-celled creatures seemingly take so long to appear? What sparked the Cambrian Explosion of new species? Was an increase in the number of species inevitable or mere chance? Is the progress of life on Earth at all relevant to expectations for life on other planets?

As to be expected, Brownlee and Ward select interpretations to best support their theory of the rarity of complex life. As frustrating as it is, we may never learn the actual answers to such difficult questions in our lifetimes, nor may humankind find out before the next big rock knocks our homeworld silly, -and life has to start from the begnning again.

Ward and Brownlee employ a clear and engaging writing style that's right for a general audience. They did annoy me by wrapping up each discussion with, "In the next chapter we will see..." I think grown up readers can do without the textbook tone. The book does offer an accessible history of ideas, and the latest scientific thought on life's origins and evolution. The book includes black and white illustrations and graphs that break up the text, but these don't compare to the exciting cover art.

My SETI screen-saver rouses itself, day-glo colors spiking mysteriously against the black void that signals my lack of keyboard activity. I've decided I'm going to keep running it. Though the RARE EARTH argument may have revised the odds, made the prospect of contact even more remote, -it'll certainly never happen if we all stop looking.

RARE EARTH: Why Complex Life is Uncommon in the Universe
Peter D. Ward and Donald Brownlee
2000
ISBN 0-387-98701-0
Copernicus
An imprint of Springer-Verlag New York, Inc.
175 Fifth Avenue, New York, NY 10010
www.copernicus-ny.com/

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