What Does a Martian Look Like?: The Science of Extraterrestrial Life

by Jack Cohen, Ian Stewart

Overview

"A fascinating and useful handbook to both the science and science fiction of extraterrestrial life. Cohen and Stewart are amusing, opinionated, and expert guides. I found it a terrific and informative piece of work-nothing else like it!"
-Greg Bear
"I loved it."
-Larry Niven
"Ever wonder about what aliens could be like? The world authority is Jack Cohen, a professional biologist who has thought long and hard about the vast realm of possibilities. This is an engaging, swiftly moving study of alien biology, a subject with bounds and constraints these authors plumb with verve and intelligence."
-Gregory Benford
"A celebration of life off Earth. A hearteningly optimistic book, giving a much-needed antidote to the pessimism of astrobiologists who maintain that we are alone in the universe-a stance based on a very narrow view of what could constitute life. A triumph of speculative nonfiction."
-Dougal Dixon, author of
After Man: A Zoology of the Future

Product Details

ISBN-13:	9780471268895
Publisher:	TURNER PUB CO
Publication date:	10/25/2002
Pages:	369
Product dimensions:	6.36(w) x 9.54(h) x 1.21(d)

About the Author

JACK COHEN is an internationally known reproductive biologist and the coauthor, with Ian Stewart, of The Collapse of Chaos and Figments of Reality.

IAN STEWART is Professor of Mathematics at Warwick Universityin the United Kingdom. Among his sixty published books are The Magical Maze and Life's Other Secret, both from Wiley.

Read an Excerpt

What Does a Martian Look Like?

The Science of Extraterrestrial Life

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By Jack Cohen Ian Stewart

John Wiley & Sons

ISBN: 0-471-26889-5

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Chapter One

Astrobiology and Xenoscience

Cain and Abel have walked and drifted in many strange places - 'walked' was not appropriate for many of them. Cain is a millipede four feet long, or alternatively one hundred and twenty-two feet along; Abel is - well, more of a gas cloud with a few solid bits, really. Our translator can give some flavour of their reactions to various Earth ecosystems, as they prepare a booklet for alien tourists. (The translator is necessarily imperfect; all alien concepts are replaced by the nearest human equivalent, however inappropriate.)

They start, as they usually do, in a desert; it is a simple ecosystem with about species. Abel sinks into the sand, while Cain turns over a flat rock. Under the rock is a small yellow scorpion, whose sting tries to penetrate Cain's armour and fails. Cain notes that the scorpion is nearly at the top of the ecosystem; he picks up a piece of its excreta and chews it thoughtfully. 'We should warn them about stings ... and about this stuff,' he says. 'It is delicious, and could be addictive. This little chap ate two beetles last week. One was a fungus-feeder, one was a little carnivore; nematode worms, mostly.'

Abel lifts partly out of the sand. 'About three or four grams of algae every square metre,' he says, 'photosynthesising like mad. Lots ofgrazers on the algae, springtails, lots of kinds of mites ... There's a fungus mat about ten centimetres down, catching all the excreta, shed skins, corpses; every couple of days it makes a set of spore-bodies at the surface, wafts spores around everywhere; only one in a million hatches, the others are eaten. Now, who's creaming off the top of this little system?'

Cain burrows feverishly in the surface layers, and reports: 'Down in that dip there's a frog who hasn't woken up for three years. It will be wet enough for him this year, he'll eat a couple of beetles and go down again. And there's a dry stream bed with lots more life under its stones ... a wind-scorpion who's just moulted: all it's had to eat is its shed cuticle; it might take a lizard some time in the next month.'

'What is there for the tourists?'

'Um ... quite a big gecko ... and with some eggs it's guarding. And on the horizon, a maned wolf - they'll like that.'

'Enough here,' Abel declares, as he makes a few notes. 'More than enough to fill a prospectus.'

'Across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish ... regarded this Earth with envious eyes, and slowly and surely drew their plans against us.' In the opening paragraph of his story The War of the Worlds, the great H.G. Wells introduced his Victorian readers to the novel concept of an alien lifeform - a creature from another planet. (Anyone who has listened to the Jeff Wayne musical version narrated by Richard Burton will find 'minds immeasurably superior to ours' more familiar, which is less clumsy to the modern ear, but the above is what Wells actually wrote.) The wide Victorian readership of Wells's books and magazine stories found little difficulty in following his imagination out to the denizens of Mars, busily planning the invasion of Earth. The Victorians revelled in the harrowing tale of blood, death, and destruction as the Martians, disembodied brains enclosed in three-legged walking machines, laid waste to their home planet - or, at least, to England, which Wells pretty much identified as the home of humanity. And they were spellbound by the unexpected ending, in which Earth is saved not by Man, but by microbes. The War of the Worlds still has the power to thrill us, even in its mostly dreadful movie incarnations, and it has given us an icon for creatures from other planets that continues, subconsciously, to influence our thoughts about alien life.

Wells also gave us other memorable SF 'tropes' - generic story concepts - such as The Time Machine and The Invisible Man, concepts that most of his readers would otherwise not have entertained in all their lives. But there is a big difference between his Martians and those other concepts. Time machines and invisibility are simply fantastic - exercises of the imagination without any correspondence in reality, whereas Martians might really have existed earlier in that planet's history. In fact, as far as Wells knew, they might have been observing the Earth while he was writing his story. Envious eyes and all.

We now know that there are many planets out there in the galaxy, and we have good grounds for supposing that a number of these will have life. Not all scientists agree with these two statements, and we will discuss - and offer some answers to - their objections later; for now, assume that what we've said can be justified. If so, then life as we know it here on Earth is but one sample among many. And our biology, therefore, is but a small sample of all those extraterrestrial biologies. It is the only biology about which we know anything by direct observation, but we really do have a lot of information about its evolutionary history and its variety. Some two thousand years of study, more than half of it carried out in the last twenty years, has provided a large and reliable database against which to test our theories. We have a rapidly growing theoretical biology that sits squarely on our knowledge of life's history and function, its biochemistry and its adaptations, and to some extent its ecology, here on Earth. Presumably much of this theory can also be applied to life processes elsewhere: the process of natural selection, for example, applies to all simple lifeforms, though perhaps not to those that have organised their environment as human beings have.

Over the last decade or so, aliens have become scientifically respectable. Groups of scientists from widely scattered areas of expertise have become interested in extraterrestrial life. Evidence of possible life on Mars has hit the headlines. In a group of NASA scientists headed by David MacKay found tiny tube-like structures in the meteorite ALH, found in Antarctica in . The tubes look rather like fossil bacteria, and there is good circumstantial evidence that the meteorite came to Earth from Mars, splashed off its surface by an impact. These 'nanobacteria' proved highly controversial; for a start, they were far smaller than Earthly bacteria. The controversy continues, but few scientists currently believe that the tubes have anything to do with Martian lifeforms. Nevertheless, the claim was taken seriously, and still is.

A new science of alien life has been emerging, but unfortunately in its most recent incarnation it has adopted the name astrobiology. It is - or, rather, claims to be - the serious science of alien life. The science is sound, often frontier work: planets encircling distant stars, the latest in genetics. As its name suggests, astrobiology is a fusion of modern astronomy and modern biology. So what's unfortunate about it?

Astronomy is about the stars, and other celestial bodies, and the key area here is the recent discovery of solid observational evidence that proves some stars other than our own have planets. Biology is also about a planet: this one. Of course the planetary aspects are in the background: biology is about living creatures that inhabit our planet. Biology is a vast and impressive subject, currently progressing at a remarkable rate; but in the context of alien life it suffers from one big drawback. It is restricted to those organisms that exist, or have existed, on Earth. Because we know so much about these organisms, it is all too easy to think that we therefore know a lot about life in general. However, there's no good reason to suppose that we do. The crucial question about alien life is: could it be radically different from life on Earth? If the answer is 'yes', then all that information about earthly lifeforms is actually misleading, and its quantity is irrelevant, along with most of its content. Of course the answer could be 'no', but our knowledge of how life works here doesn't imply that nothing else could do a similar job, and strongly suggests that there could be radically different alternatives. SETI, the Search for Extra-Terrestrial Intelligence, assumes that aliens will be much like us in all important respects, and in particular will develop technology and communicate by radio - but this assumption could be completely misguided. Absence of evidence is not evidence of absence, at least unless you've looked very hard for the evidence and not found any.

What this means is that astrobiology is the science of Earthlike planets supporting Earthlike life. It is, by and large, now. But many of the great pioneers like Carl Sagan, whose imagination was much wider, called themselves astrobiologists. And there are many mavericks now, esconced in that community but considering far-out possibilities. Today, then, astrobiology is an interesting topic, but it might be a very limited and narrow-minded one. And that's why the name, or more precisely, the attitude that it betrays, is unfortunate. Whether the current approach is too limited depends on whether the universe is like Star Trek, with humanoid aliens lurking on nearly every planet and few other kinds of alien anywhere (though Star Trek does also have an occasional very weird alien, such as a creature made solely of energy, to add a little variety without taxing the Effects Department too much). If we really live in a Star Trek universe, then astrobiology is entirely appropriate and we need nothing more; but we can't logically establish that if we start out by assuming it. It has to be a central part of the argument, not something that never even gets questioned. So, whatever the answer, astrobiology in its current form is by its nature too narrow-minded and too unimaginative to tackle the really big questions about aliens.

What else is there? Ever since the s, the SF fraternity has been discussing xenobiology. This is a much better word. The Greek 'xenos' means 'strange', so xenobiology is, by definition, the biology of the strange. Of course very little xenobiology exists, though there is actually more than you might think, because many people have worked on theoretical alternatives to conventional life. Some references can be found in our technical reading list. But there's no useful body of observational xenobiology yet, and there won't be until (if ever) we come into contact with alien lifeforms.

Why, then, do today's scientists call the subject 'astrobiology'? Possibly because nobody learns Greek any more ... but mainly because astrobiology was invented by astronomers who had a smattering of biology. If it had been invented by biologists who had a smattering of astronomy, it would have been called bioastronomy, but modern biologists are far too busy raising venture capital for biotechnology companies to worry about aliens. In fact, there is such a discipline. Jonathan Cowie lectures about it, telling his students as an example how coral layering in the Jurassic period can tell us that the Moon was nearer to the Earth then, with a shorter month. Either way, the name astrobiology itself is a warning: it betrays an unimaginative approach to a subject that absolutely cries out for imagination. Instead of opening up new worlds, new habitats, new types of lifelike organisation, astrobiology narrows everything down into two existing areas of science. One of which has its feet firmly set on Mother Earth, while the other is mostly looking for duplicates of Mother Earth.

There's a problem with the word 'xenobiology', too: it tacitly assumes that the way to make progress is to focus on the biology of aliens. In reality, the whole area has to be interdisciplinary. The biology is intimately entwined with the planetary science, and conversely. So as this book progresses, we will argue the case for a much wider kind of thinking - which, for ease of reference, we'll call 'xenoscience'. It's a pity that this is one of those graeco-latin hybrids, like 'television' and 'pentium', but 'xenology' doesn't sound like an interdisciplinary area, so we'll have to make the best of a bad job.

Our central theme will be the inadequacy of astrobiology and the need to replace it by xenoscience. Along the way we will point out some of the existing contributions to the foundations of this intriguing new science, and we will try to guess what xenoscience will eventually look like when some of the most glaring gaps are filled in. What we will not do is try to lay the foundations for xenoscience. That will need a lot of work by many people, and it can't be done in one popular science book. But we'll peer through the veil of the future, and try to see what might be built once those foundations have been made solid.

As things stand right now, xenoscience is a theoretical subject based on two kinds of information. Firstly, there is the one real example that we have to hand, which has generated an enormous database: Earth's biota. ('Biota' is a fancy word for 'lifeforms', the creatures that make up an ecosystem.) Secondly, and with far more authority than the bald data itself, we have the accumulated and tested knowledge of how Earth's living things began, and how they work, compete, die out, or change, through geological time.

Given this, it seems very strange that the most prolific, and apparently authoritative, science of extraterrestrial life has been written by astrophysicists. It is as if the chemistry of organic compounds had been written about by biologists, or the physics of stars by mathematicians. Of course, in appropriate circumstances it is entirely proper that this kind of discipline-hopping should occur: mathematicians, in particular, have made a speciality of extracting broad general concepts from a few examples, and then testing their universality very stringently. But it's not appropriate for a science of alien life. If we wish to apply the wisdom of biology to questions about aliens, then we must use the best biological knowledge that we have, both database and theory. Freshman Biology . is inadequate for the task. It is absurd to talk of the evolution of aliens, for example, using the 'folk' evolution models of the s instead of today's better-informed models based in work on wild populations from the s to the s. Astrophysicists, by and large, seem not to have realised that there has been a revolution in evolutionary thinking during the s, just as radical as the Newton/Einstein paradigm shift in physics.

One consequence of this reliance on folk biology is that astrobiologists are ruling out various scenarios for alien life, even though those scenarios already occur on this planet.

Continues...

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Excerpted from What Does a Martian Look Like? by Jack Cohen Ian Stewart Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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Table of Contents

	Preface	vii
	Acknowledgements	xiii
1	Astrobiology and Xenoscience	1
2	The Invisible Book	29
3	Aliens, Aliens and Aliens	47
4	Not-Quite Life	64
5	Possibilities of Life	90
6	The Drake Equation	116
7	The Evolution of Alien Life	144
8	Dragons, Teddy Bears, and Toddlers	170
9	Modelling Alien Ecosystems	187
10	Not As We Know It	210
11	The Sensual Tribble	243
12	The Universality of Extelligence	276
13	Have Aliens Visited Us?	309
14	Galactic Empires	334
	Popular Xenoscience Reading List	346
	Technical Xenoscience Reading List	349
	Index	355

What People are Saying About This

Dougal Dixon

A celebration of life off Earth. A hearteningly optimistic book, giving a much-needed antidote to the pessimism of astrobiologists who maintain that we are alone in the universe–a stance based on a very narrow view of what could constitute life. A triumph of speculative nonfiction.
—Dougal Dixon, author of After Man: A Zoology of the Future

Larry Niven

I loved it.

Gregory Benford

Ever wonder about what aliens could be like? The world authority is Jack Cohen, a professional biologist who has thought long and hard about the vast realm of possibilities. This is an engaging, swiftly moving study of alien biology, a subject with bounds and constraints these authors plumb with verve and intelligence.

Greg Bear

A fascinating and useful handbook to both the science and science fiction of extraterrestrial life. Cohen and Stewart are amusing, opinionated, and expert guides. I found it a terrific and informative piece of work–nothing else like it!