Paul Davies’s subtitle might lead readers to suspect that he is one of the band of scientists out to prove the existence of God. This idea will be dispelled quickly as readers delve into the searching questions that Davies raises and into the scientific evidence he brings to this extraordinary study. Although he deals with extremely complex biogenetic and astronomical material, he writes with sufficient lucidity and vigor that reading The Fifth Miracle is akin to reading a fast-moving, compelling adventure story.

Davies, a theoretical physicist with over twenty books to his credit, was raised and educated in the environs of London, but now lives in South Australia. His guiding principle, stated well into the book, seems to be “the dictum that the absence of evidence is not the same as evidence of absence.” He approaches his subject with a healthy skepticism but always with a mind sufficiently open that it does not confuse absence of evidence with evidence of absence.

This attitude has led him to state the probability that there is life on Mars, and, possibly, on other planets as well. At present, conditions on Jupiter’s moon Europa appear to favor the presence of life on that planet, and the very vastness of space offers the possibility that life once existed or currently exists on planets other than Earth.

One must be cautioned that when Davies writes about life on Mars, he is not suggesting the presence of little green people with antennas protruding from their foreheads. He is talking about much lower forms of life, the very forms that inhabited the primordial ooze on Earth during its formative stages. Once these forms have been established, it may be merely a matter of time before more complex forms evolve, although all sorts of variables must be in place before this can happen.

In a most compelling chapter entitled “Mars: Red and Dead?” which for many will be the most interesting chapter in a thoroughly enticing book, Davies offers persuasive evidence that Mars, known to have had, far back in its history, both water and a relatively mild climate, may once have supported life. He goes so far as to speculate that certain life-forms, particularly bacteria, may still exist in the depths of the planet far below its ice caps, which may contain areas heated geothermally from the planet’s core.

In support of these highly controversial speculations, Davies cites the conclusions that Mars expert Chris McKay, who works as a researcher for the National Aeronautics and Space Administration (NASA), reached regarding the presence of petrified husks of microbes in a rock, ALH84001, that has definitely been identified as being from Mars. It has been established that it fell into Antarctica near Allan Hills some thirteen thousand years ago following an estimated sixteen-million-year journey through outer space. Roberta Score, a member of the United States Antarctica Search of Meteors team in 1984, found ALH84001 lying on the edge of an ice field.

The rock had never been touched by human hands and was fully protected from contamination before it was sent to Houston under frozen conditions for analyses that have continued during the intervening years. More sensitive instruments and a greater understanding of Mars and of outer space have provided increasingly sophisticated means of conducting the ongoing analyses.

Davies is well aware of the major arguments that some of his fellow scientists have formulated casting doubt on his contentions, but he responds to such arguments with verifiable scientific facts that generally counter, and at times obliterate, his opponents’ skepticism. In writing about the meteorite that fell near the Australian town of Murchison on September 28, 1969, and has been subjected to extensive scientific analysis ever since, he concludes categorically:

There are objects in space loaded with just the sort of organic compounds needed for life to get started. It does not require a primordial soup on Earth to synthesize the building blocks of life. These substances can fall from the sky, ready-made.

Analyses of the Murchison meteorite support Davies’s speculative theory that early forms of life may originally have come to Earth from other planets and, finding a hospitable environment, have flourished to the point of development that life on this planet has eventually reached. He cautions that one must not assume that life can exist only under conditions that are known to support life as most people know it. He refers to the vents in the bottom of Earth’s oceans that spew forth water at close to a thousand degrees Fahrenheit, but that have living organisms growing around them in heat that most people would consider much greater than that in which any living organism could survive.

He asks his readers to suppose the possibility that some microbes exist in the depths of Earth’s deepest oceans that resemble or are identical to those of the primeval planet Earth, that are like those that existed at the very beginning of life on the planet. These microbes would not have changed perceptibly since the dawn of life and might hold clues to life’s origins.

Part of what makes Davies’s book as accessible as it is to those unfamiliar with his field is his ability to make apt analogies that any reader can follow quite easily. In discussing what life is, how it can be defined in workable ways, he asks what a steam locomotive is and how it works. He goes on to recount how a locomotive engineer (metaphorically, a biogenetic scientist) could provide detailed information about the locomotive’s pistons and governors and steam pressure. He might also talk about the thermodynamics of combustion, but in doing so the engineer would be skirting the issue. Davies contends that what needs to be elucidated is, in terms that suggest Plato’s theory of innate ideas as presented in the Allegory of the Cave, the “traininess” of the locomotive, the inherent quality that endows it with its power and majesty.

One can, in Davies’s view, try to define life in terms of several matters that he spells out and discusses, among them reproduction, metabolism, nutrition, complexity, organization, growth and development, and information content. These items, however—each of which contains inherent contradictions that Davies is quick to point out—do not provide the answer to how life can be defined. These are elements fundamental to life, but the “lifeness” that must underlie any valid definition of life is absent.

In several places in his study, Davies focuses on the relation of information technology to life. Information that is passed on from one generation to the next is found in deoxyribonucleic acid (DNA), the intrinsic blueprint of all living things. It alone, however, is meaningless without context. Fallen leaves in a forest contain information, but, in Davies’s view, this information does not mean anything outside a context. Such leaves might mean little or nothing to some observers but a great deal to a team of detectives trying to track down a fugitive. Davies makes many of his important points through analogies like this one.

Discussing the possibility of finding life on Mars, or at least evidence that life has existed on that planet, Davies reminds readers that NASA’s space probes that have landed rovers on the face of Mars have ferreted out the safest landing sites. Such sites, however, are not where evidence of present or past life on the planet is most likely to be found. Favorable landing sites are in extended flat areas. Evidence of life is most likely to be found in the better-protected mountainous regions of this planet, one of which contains the volcano Olympus Mons, a mountain seven times as high as Mount Everest. Its volcanic crater has a diameter of nearly 350 miles (550 kilometers).

Life is most likely to be found where volcanoes and water meet, engendering hot springs that are hospitable to rudimentary life. Olympus Mons was an active volcano for billions of years during which Mars is known to have had rivers and lakes. The conditions existed for hot springs to develop around thermal vents.

Davies has not completely written off the possibility that Mars’s volcanoes may still show some activity, despite millions of years of inactivity. He writes: “Since it is unlikely that Mars would be volcanically active for four billion years only to cease relatively recently, it seems reasonable to conclude that some hot spots still exist, probably deep underground.” If there is heat in the inner core of Olympus Mons or other Martian volcanoes, then the conditions for primitive life-forms may still conceivably be present.

Davies explains some of the puzzling topography of Mars. Its dry river valleys have a chaotic terrain covered with tangled masses of rocks. His explanation of these configurations is that when molten rock from volcanoes ran into the ground ice, much of the ice melted, causing the land beneath it to collapse in a random manner. If this contention is valid, then such places, which are virtually impossible to access with the kinds of rovers NASA has thus far sent to Mars, would have been the most likely sites in which to find the hydrothermal systems that could support life.

There is no infallible, absolute answer to how life originated, as Davies clearly demonstrates. Perhaps life is “the consequence of a random and purely incidental quirk of fate,” as French biologist Jacques Monod, whom Davies quotes, suggests. Davies does not dismiss this possibility, but he also raises the possibility that life results from laws of nature that are as immutable as the laws of physics.

It is clear from considering Davies’s contentions that Charles Darwin’s pioneering strides toward understanding the origins of complex forms of life provide inadequate explanations as science moves into new realms made possible through the development of new technologies. One must now consider the possibility that interplanetary cross-fertilization has taken place for the billions of years that the universe has existed. Finding ALH84001 in Antarctica and the Murchison meteorite in Australia opens the door to such a possibility.

Earth is bombarded by tons of debris from Mars and other planets every year. Much of this material lies unrecognized. Over time, contamination makes it of limited scientific value. The fact that ALH84001 fell into the relatively antiseptic environment of Antarctica and was preserved by that continent’s remarkably dry, subfreezing climate for thirteen millennia makes it a rare and wonderful find. A recent computer calculation suggests that 7.5 percent of all the rocks ejected from Mars will eventually fall on Earth, with a like percentage falling on Venus and about 38 percent burning up in the sun’s atmosphere.

It is known that bacteria are unbelievably adaptable and that they can enter states of suspended animation for incredible lengths of time. A percentage of those embedded in planetary rocks can withstand devastatingly high temperatures and, because of their small size, not be crushed by the near-pulverizing pressures exerted on the rocks as they catapult into space.

Within the protective confines of rocks, bacteria can enter a suspended state and live for centuries and, in some cases, for millions of years. Davies tells about Chris McKay’s finding three-million-year-old microorganisms in the Siberian permafrost. Forty-four-million-year-old bacteria taken from inside a bee encased in amber have been cloned. Science is on the brink of rewriting the whole story of creation, perhaps in terms like those that Davies spells out in his intriguing book.

Sources for Further Study

Booklist 95 (February 1, 1999): 951.

The Christian Century 116 (June 2, 1999): 622.

Library Journal 124 (February 1, 1999): 116.

The New York Times Book Review 104 (April 18, 1999): p. 12.

Publishers Weekly 246 (February 22, 1999): 78.

School Library Journal 45 (April, 1999): 117.