RICHARD DAWKINS THE BLIND WATCHMAKER
RICHARD DAWKINS THE BLIND WATCHMAKER PENGUIN BOOKS RICHARD DAWKINS THE BLIND WATCHMAKER
ABOUT THE AUTHOR Richard Dawkins was born in Nairobi in 1941.He was educated at Oxford University,and after graduation remained there to work for his doctorate with the Nobel Prize-winning ethologist Niko Tinbergen.From 1967 to 1969 he was an Assistant Professor of Zoology at the University of California at Berkeley.In 1970 he became a Lecturer in Zoology at Oxford University and a Fellow of New College.In 1995 he became the first Charles Simonyi Professor of the Public Understanding of Science at Oxford University Richard Dawkins's first book.The Selfish Gene (1976;second edition, 1989),became an immediate international bestseller and,like The Blind Watchmaker,was translated into all the major languages.Its sequel,The Extended Phenotype,followed in 1982.His other best- sellers include River Out of Eden (1995)and Climbing Mount Improbable (1996;Penguin,1997). Richard Dawkins won both the Royal Society of Literature Award and the Los Angeles Times Literary Prize in 1987 for The Blind Watchmaker.The television film of the book,shown in the Horizon series,won the Sci-Tech Prize for the Best Science Programme of 1987. He has also won the 1989 Silver Medal of the Zoological Society of London and the 1990 Royal Society Michael Faraday Award for the furtherance of the public understanding of science.In 1994 he won the Nakayama Prize for Human Science and has been awarded an Honorary D.Litt.by the University of St Andrews and by the Australian National University,Canberra
ABOUT THE AUTHOR Richard Dawkins was born in Nairobi in 1941. He was educated at Oxford University, and after graduation remained there to work for his doctorate with the Nobel Prize-winning ethologist Niko Tinbergen. From 1967 to 1969 he was an Assistant Professor of Zoology at the University of California at Berkeley. In 1970 he became a Lecturer in Zoology at Oxford University and a Fellow of New College. In 1995 he became the first Charles Simonyi Professor of the Public Understanding of Science at Oxford University. Richard Dawkins's first book. The Selfish Gene (1976; second edition, 1989), became an immediate international bestseller and, like The Blind Watchmaker, was translated into all the major languages. Its sequel, The Extended Phenotype, followed in 1982. His other bestsellers include River Out of Eden (1995) and Climbing Mount Improbable (1996; Penguin, 1997). Richard Dawkins won both the Royal Society of Literature Award and the Los Angeles Times Literary Prize in 1987 for The Blind Watchmaker. The television film of the book, shown in the Horizon series, won the Sci-Tech Prize for the Best Science Programme of 1987. He has also won the 1989 Silver Medal of the Zoological Society of London and the 1990 Royal Society Michael Faraday Award for the furtherance of the public understanding of science. In 1994 he won the Nakayama Prize for Human Science and has been awarded an Honorary D.Litt. by the University of St Andrews and by the Australian National University, Canberra
CONTENTS Preface Chapter I Explaining the very improbable Chapter 2 Good design Chapter 3 Accumulating small change Chapter 4 Making tracks through animal space Chapter 5 The power and the archives Chapter 6 Origins and miracles Chapter 7 Constructive evolution Chapter 8 Explosions and spirals Chapter 9 Puncturing punctuationism Chapter 10 The one true tree of life Chapter 11 Doomed rivals Bibliography Appendix (1991):Computer programs and"The Evolution of Evolvability' Index
CONTENTS Preface Chapter I Explaining the very improbable Chapter 2 Good design Chapter 3 Accumulating small change Chapter 4 Making tracks through animal space Chapter 5 The power and the archives Chapter 6 Origins and miracles Chapter 7 Constructive evolution Chapter 8 Explosions and spirals Chapter 9 Puncturing punctuationism Chapter 10 The one true tree of life Chapter 11 Doomed rivals Bibliography Appendix (1991): Computer programs and 'The Evolution of Evolvability' Index
PREFACE This book is written in the conviction that our own existence once presented the greatest of all mysteries,but that it is a mystery no longer because it is solved.Darwin and Wallace solved it,though we shall continue to add footnotes to their solution for a while yet.I wrote the book because I was surprised that so many people seemed not only unaware of the elegant and beautiful solution to this deepest of problems but,incredibly,in many cases actually unaware that there was a problem in the first place! The problem is that of complex design.The computer on which I am writing these words has an information storage capacity of about 64 kilobytes (one byte is used to hold each character of text).The computer was consciously designed and deliberately manufactured. The brain with which you are understanding my words is an array of some ten million kiloneurones.Many of these billions of nerve cells have each more than a thousand 'electric wires'connecting them to other neurones.Moreover,at the molecular genetic level,every single one of more than a trillion cells in the body contains about a thousand times as much precisely-coded digital information as my entire computer.The complexity of living organisms is matched by the elegant efficiency of their apparent design.Ifanyone doesn't agree that this amount of complex design cries out for an explanation,I give up. No,on second thoughts I don't give up,because one of my aims in the book is to convey something of the sheer wonder of biological complexity to those whose eyes have not been opened to it.But having built up the mystery,my other main aim is to remove it again by explaining the solution. xiii
PREFACE This book is written in the conviction that our own existence once presented the greatest of all mysteries, but that it is a mystery no longer because it is solved. Darwin and Wallace solved it, though we shall continue to add footnotes to their solution for a while yet. I wrote the book because I was surprised that so many people seemed not only unaware of the elegant and beautiful solution to this deepest of problems but, incredibly, in many cases actually unaware that there was a problem in the first place! The problem is that of complex design. The computer on which I am writing these words has an information storage capacity of about 64 kilobytes (one byte is used to hold each character of text). The computer was consciously designed and deliberately manufactured. The brain with which you are understanding my words is an array of some ten million kiloneurones. Many of these billions of nerve cells have each more than a thousand 'electric wires' connecting them to other neurones. Moreover, at the molecular genetic level, every single one of more than a trillion cells in the body contains about a thousand times as much precisely-coded digital information as my entire computer. The complexity of living organisms is matched by the elegant efficiency of their apparent design. If anyone doesn't agree that this amount of complex design cries out for an explanation, I give up. No, on second thoughts I don't give up, because one of my aims in the book is to convey something of the sheer wonder of biological complexity to those whose eyes have not been opened to it. But having built up the mystery, my other main aim is to remove it again by explaining the solution. xiii
XIV Preface Explaining is a difficult art.You can explain something so that your reader understands the words;and you can explain something so that the reader feels it in the marrow of his bones.To do the latter,it sometimes isn't enough to lay the evidence before the reader in a dispassionate way.You have to become an advocate and use the tricks of the advocate's trade.This book is not a dispassionate scientific treatise.Other books on Darwinism are,and many of them are excellent and informative and should be read in conjunction with this one.Far from being dispassionate,it has to be confessed that in parts this book is written with a passion which,in a professional scientific journal,might excite comment.Certainly it seeks to inform,but it also seeks to persuade and even one can specify aims without presumption-to inspire.I want to inspire the reader with a vision of our own existence as,on the face of it,a spine-chilling mystery,and simultaneously to convey the full excitement of the fact that it is a mystery with an elegant solution which is within our grasp.More,I want to persuade the reader,not just that the Darwinian world-view happens to be true,but that it is the only known theory that could,in principle,solve the mystery of our existence.This makes it a doubly satisfying theory.A good case can be made that Darwinism is true,not just on this planet but all over the universe wherever life may be found. In one respect I plead to distance myself from professional advocates. A lawyer or a politician is paid to exercise his passion and his persuasion on behalf of a client or a cause in which he may not privately believe.I have never done this and I never shall.I may not always be right,but I care passionately about what is true and I never say anything that I do not believe to be right.I remember being shocked when visiting a university debating society to debate with creationists.At dinner after the debate,I was placed next to a young woman who had made a relatively powerful speech in favour of creationism.She clearly couldn't be a creationist,so I asked her to tell me honestly why she had done it.She freely admitted that she was simply practising her debating skills,and found it more challenging to advocate a position in which she did not believe. Apparently it is common practice in university debating societies for speakers simply to be told on which side they are to speak.Their own beliefs don't come into it.I had come a long way to perform the disagreeable task of public speaking,because I believed in the truth of the motion that I had been asked to propose.When I discovered that members of the society were using the motion as a vehicle for playing arguing games,I resolved to decline future invitations from debating societies that encourage insincere advocacy on issues where scientific truth is at stake
XIV Preface Explaining is a difficult art. You can explain something so that your reader understands the words; and you can explain something so that the reader feels it in the marrow of his bones. To do the latter, it sometimes isn't enough to lay the evidence before the reader in a dispassionate way. You have to become an advocate and use the tricks of the advocate's trade. This book is not a dispassionate scientific treatise. Other books on Darwinism are, and many of them are excellent and informative and should be read in conjunction with this one. Far from being dispassionate, it has to be confessed that in parts this book is written with a passion which, in a professional scientific journal, might excite comment. Certainly it seeks to inform, but it also seeks to persuade and even - one can specify aims without presumption - to inspire. I want to inspire the reader with a vision of our own existence as, on the face of it, a spine-chilling mystery, and simultaneously to convey the full excitement of the fact that it is a mystery with an elegant solution which is within our grasp. More, I want to persuade the reader, not just that the Darwinian world-view happens to be true, but that it is the only known theory that could, in principle, solve the mystery of our existence. This makes it a doubly satisfying theory. A good case can be made that Darwinism is true, not just on this planet but all over the universe wherever life may be found. In one respect I plead to distance myself from professional advocates. A lawyer or a politician is paid to exercise his passion and his persuasion on behalf of a client or a cause in which he may not privately believe. I have never done this and I never shall. I may not always be right, but I care passionately about what is true and I never say anything that I do not believe to be right. I remember being shocked when visiting a university debating society to debate with creationists. At dinner after the debate, I was placed next to a young woman who had made a relatively powerful speech in favour of creationism. She clearly couldn't be a creationist, so I asked her to tell me honestly why she had done it. She freely admitted that she was simply practising her debating skills, and found it more challenging to advocate a position in which she did not believe. Apparently it is common practice in university debating societies for speakers simply to be told on which side they are to speak. Their own beliefs don't come into it. I had come a long way to perform the disagreeable task of public speaking, because I believed in the truth of the motion that I had been asked to propose. When I discovered that members of the society were using the motion as a vehicle for playing arguing games, I resolved to decline future invitations from debating societies that encourage insincere advocacy on issues where scientific truth is at stake
Preface XV For reasons that are not entirely clear to me,Darwinism seems more in need of advocacy than similarly established truths in other branches of science.Many of us have no grasp of quantum theory,or Einstein's theories of special and general relativity,but this does not in itself lead us to oppose these theories!Darwinism,unlike 'Einsteinism', seems to be regarded as fair game for critics with any degree of ignorance.I suppose one trouble with Darwinism is that,as Jacques Monod perceptively remarked,everybody thinks he understands it.It is,indeed,a remarkably simple theory;childishly so,one would have thought,in comparison with almost all of physics and mathematics.In essence,it amounts simply to the idea that non-random reproduction, where there is hereditary variation,has consequences that are far-reaching if there is time for them to be cumulative.But we have good grounds for believing that this simplicity is deceptive.Never forget that,simple as the theory may seem,nobody thought of it until Darwin and Wallace in the mid nineteenth century,nearly 200 years after Newton's Principia,and more than 2,000 years after Eratosthenes measured the Earth.How could such a simple idea go so long undiscovered by thinkers of the calibre of Newton,Galileo,Descartes, Leibnitz,Hume and Aristotle?Why did it have to wait for two Victorian naturalists?What was wrong with philosophers and mathematicians that they overlooked it?And how can such a powerful idea go still largely unabsorbed into popular consciousness? It is almost as if the human brain were specifically designed to misunderstand Darwinism,and to find it hard to believe.Take,for instance,the issue of 'chance',often dramatized as blind chance.The great majority of people that attack Darwinism leap with almost unseemly eagerness to the mistaken idea that there is nothing other than random chance in it.Since living complexity embodies the very antithesis of chance,if you think that Darwinism is tantamount to chance you'll obviously find it easy to refute Darwinism!One of my tasks will be to destroy this eagerly believed myth that Darwinism is a theory of 'chance'.Another way in which we seem predisposed to disbelieve Darwinism is that our brains are built to deal with events on radically different timescales from those that characterize evolution- ary change.We are equipped to appreciate processes that take seconds, minutes,years or,at most,decades to complete.Darwinism is a theory of cumulative processes so slow that they take between thousands and millions of decades to complete.All our intuitive judgements of what is probable turn out to be wrong by many orders of magnitude.Our .well-tuned apparatus of scepticism and subjective probability-theory misfires by huge margins,because it is tuned-ironically,by evolution
Preface xv For reasons that are not entirely clear to me, Darwinism seems more in need of advocacy than similarly established truths in other branches of science. Many of us have no grasp of quantum theory, or Einstein's theories of special and general relativity, but this does not in itself lead us to oppose these theories! Darwinism, unlike 'Einsteinism', seems to be regarded as fair game for critics with any degree of ignorance. I suppose one trouble with Darwinism is that, as Jacques Monod perceptively remarked, everybody thinks he understands it. It is, indeed, a remarkably simple theory; childishly so, one would have thought, in comparison with almost all of physics and mathematics. In essence, it amounts simply to the idea that non-random reproduction, where there is hereditary variation, has consequences that are far-reaching if there is time for them to be cumulative. But we have good grounds for believing that this simplicity is deceptive. Never forget that, simple as the theory may seem, nobody thought of it until Darwin and Wallace in the mid nineteenth century, nearly 200 years after Newton's Principia, and more than 2,000 years after Eratosthenes measured the Earth. How could such a simple idea go so long undiscovered by thinkers of the calibre of Newton, Galileo, Descartes, Leibnitz, Hume and Aristotle? Why did it have to wait for two Victorian naturalists? What was wrong with philosophers and mathematicians that they overlooked it? And how can such a powerful idea go still largely unabsorbed into popular consciousness? It is almost as if the human brain were specifically designed to misunderstand Darwinism, and to find it hard to believe. Take, for instance, the issue of 'chance', often dramatized as blind chance. The great majority of people that attack Darwinism leap with almost unseemly eagerness to the mistaken idea that there is nothing other than random chance in it. Since living complexity embodies the very antithesis of chance, if you think that Darwinism is tantamount to chance you'll obviously find it easy to refute Darwinism! One of my tasks will be to destroy this eagerly believed myth that Darwinism is a theory of 'chance'. Another way in which we seem predisposed to disbelieve Darwinism is that our brains are built to deal with events on radically different timescales from those that characterize evolutionary change. We are equipped to appreciate processes that take seconds, minutes, years or, at most, decades to complete. Darwinism is a theory of cumulative processes so slow that they take between thousands and millions of decades to complete. All our intuitive judgements of what is probable turn out to be wrong by many orders of magnitude. Our •well-tuned apparatus of scepticism and subjective probability-theory misfires by huge margins, because it is tuned - ironically, by evolution
XVI Preface itself-to work within a lifetime of a few decades.It requires effort of the imagination to escape from the prison of familiar timescale,an effort that I shall try to assist. A third respect in which our brains seem predisposed to resist Darwinism stems from our great success as creative designers.Our world is dominated by feats of engineering and works of art.We are entirely accustomed to the idea that complex elegance is an indicator of premeditated,Grafted design.This is probably the most powerful reason for the belief,held by the vast majority of people that have ever lived,in some kind of supernatural deity.It took a very large leap of the imagination for Darwin and Wallace to see that,contrary to all intuition,there is another way and,once you have understood it,a far more plausible way,for complex 'design'to arise out of primeval simplicity.A leap of the imagination so large that,to this day,many people seem still unwilling to make it.It is the main purpose of this book to help the reader to make this leap. Authors naturally hope that their books will have lasting rather than ephemeral impact.But any advocate,in addition to putting the timeless part of his case,must also respond to contemporary advocates of opposing,or apparently opposing,points of view.There is a risk that some of these arguments,however hotly they may rage today,will seem terribly dated in decades to come.The paradox has often been noted that the first edition of The Origin of Species makes a better case than the sixth.This is because Darwin felt obliged,in his later editions,to respond to contemporary criticisms of the first edition, criticisms which now seem so dated that the replies to them merely get in the way,and in places even mislead.Nevertheless,the temptation to ignore fashionable contemporary criticisms that one suspects of being nine days'wonders is a temptation that should not be indulged,for reasons of courtesy not just to the critics but to their otherwise confused readers.Though I have my own private ideas on which chapters of my book will eventually prove ephemeral for this reason,the reader-and time-must judge. I am distressed to find that some women friends (fortunately not many)treat the use of the impersonal masculine pronoun as if it showed intention to exclude them.If there were any excluding to be done (happily there isn't)I think I would sooner exclude men,but when I once tentatively tried referring to my abstract reader as 'she',a feminist denounced me for patronizing condescension:I ought to say he-or-she',and 'his-or-her'.That is easy to do if you don't care about language,but then if you don't care about language you don't deserve readers of either sex.Here,I have returned to the normal conventions
XVI Preface itself - to work within a lifetime of a few decades. It requires effort of the imagination to escape from the prison of familiar timescale, an effort that I shall try to assist. A third respect in which our brains seem predisposed to resist Darwinism stems from our great success as creative designers. Our world is dominated by feats of engineering and works of art. We are entirely accustomed to the idea that complex elegance is an indicator of premeditated, Grafted design. This is probably the most powerful reason for the belief, held by the vast majority of people that have ever lived, in some kind of supernatural deity. It took a very large leap of the imagination for Darwin and Wallace to see that, contrary to all intuition, there is another way and, once you have understood it, a far more plausible way, for complex 'design' to arise out of primeval simplicity. A leap of the imagination so large that, to this day, many people seem still unwilling to make it. It is the main purpose of this book to help the reader to make this leap. Authors naturally hope that their books will have lasting rather than ephemeral impact. But any advocate, in addition to putting the timeless part of his case, must also respond to contemporary advocates of opposing, or apparently opposing, points of view. There is a risk that some of these arguments, however hotly they may rage today, will seem terribly dated in decades to come. The paradox has often been noted that the first edition of The Origin of Species makes a better case than the sixth. This is because Darwin felt obliged, in his later editions, to respond to contemporary criticisms of the first edition, criticisms which now seem so dated that the replies to them merely get in the way, and in places even mislead. Nevertheless, the temptation to ignore fashionable contemporary criticisms that one suspects of being nine days' wonders is a temptation that should not be indulged, for reasons of courtesy not just to the critics but to their otherwise confused readers. Though I have my own private ideas on which chapters of my book will eventually prove ephemeral for this reason, the reader - and time - must judge. I am distressed to find that some women friends (fortunately not many) treat the use of the impersonal masculine pronoun as if it showed intention to exclude them. If there were any excluding to be done (happily there isn't) I think I would sooner exclude men, but when I once tentatively tried referring to my abstract reader as 'she', a feminist denounced me for patronizing condescension: I ought to say 'he-or-she', and 'his-or-her'. That is easy to do if you don't care about language, but then if you don't care about language you don't deserve readers of either sex. Here, I have returned to the normal conventions
Preface xvii of English pronouns.I may refer to the 'reader'as 'he',but I no more think of my readers as specifically male than a French speaker thinks of a table as female.As a matter of fact I believe I do,more often than not,think of my readers as female,but that is my personal affair and I'd hate to think that such considerations impinged on how I use my native language. Personal,too,are some of my reasons for gratitude.Those to whom I cannot do justice will understand.My publishers saw no reason to keep from me the identities of their referees (not 'reviewers'-true reviewers,pace many Americans under 40,criticize books only after they are published,when it is too late for the author to do anything about it),and I have benefited greatly from the suggestions of John Krebs (again),John Durant,Graham Cairns-Smith,leffrey Levinton, Michael Ruse,Anthony Hallam and David Pye.Richard Gregory kindly criticized Chapter 12,and the final version has benefited from its complete excision.Mark Ridley and Alan Grafen,now no longer even officially my students,are,together with Bill Hamilton,the leading lights of the group of colleagues with whom I discuss evolution and from whose ideas I benefit almost daily.They,Pamela Wells,Peter Atkins and John Dawkins have helpfully criticized various chapters for me.Sarah Bunney made numerous improvements,and John Cribbin corrected a major error.Alan Grafen and Will Atkinson advised on computing problems,and the Apple Macintosh Syndicate of the Zoology Department kindly allowed their laser printer to draw biomorphs. Once again I have benefited from the relentless dynamism with which Michael Rodgers,now of Longman,carries all before him.He, and Mary Cunnane of Norton,skilfully applied the accelerator (to my morale)and the brake(to my sense of humour)when each was needed. Part of the book was written during a sabbatical leave kindly granted by the Department of Zoology and New College.Finally-a debt I should have acknowledged in both my previous books-the Oxford tutorial system and my many tutorial pupils in zoology over the years have helped me to practise what few skills I may have in the difficult art of explaining. Richard Dawkins Oxford.1986
Preface xvii of English pronouns. I may refer to the 'reader' as 'he', but I no more think of my readers as specifically male than a French speaker thinks of a table as female. As a matter of fact I believe I do, more often than not, think of my readers as female, but that is my personal affair and I'd hate to think that such considerations impinged on how I use my native language. Personal, too, are some of my reasons for gratitude. Those to whom I cannot do justice will understand. My publishers saw no reason to keep from me the identities of their referees (not 'reviewers' - true reviewers, pace many Americans under 40, criticize books only after they are published, when it is too late for the author to do anything about it), and I have benefited greatly from the suggestions of John Krebs (again), John Durant, Graham Cairns-Smith, leffrey Levinton, Michael Ruse, Anthony Hallam and David Pye. Richard Gregory kindly criticized Chapter 12, and the final version has benefited from its complete excision. Mark Ridley and Alan Grafen, now no longer even officially my students, are, together with Bill Hamilton, the leading lights of the group of colleagues with whom I discuss evolution and from whose ideas I benefit almost daily. They, Pamela Wells, Peter Atkins and John Dawkins have helpfully criticized various chapters for me. Sarah Bunney made numerous improvements, and John Cribbin corrected a major error. Alan Grafen and Will Atkinson advised on computing problems, and the Apple Macintosh Syndicate of the Zoology Department kindly allowed their laser printer to draw biomorphs. Once again I have benefited from the relentless dynamism with which Michael Rodgers, now of Longman, carries all before him. He, and Mary Cunnane of Norton, skilfully applied the accelerator (to my morale) and the brake (to my sense of humour) when each was needed. Part of the book was written during a sabbatical leave kindly granted by the Department of Zoology and New College. Finally - a debt I should have acknowledged in both my previous books - the Oxford tutorial system and my many tutorial pupils in zoology over the years have helped me to practise what few skills I may have in the difficult art of explaining. Richard Dawkins Oxford, 1986
CHAPTER 1 EXPLAINING THE VERY IMPROBABLE We animals are the most complicated things in the known universe. The universe that we know,of course,is a tiny fragment of the actual universe.There may be yet more complicated objects than us on other planets,and some of them may already know about us.But this doesn't alter the point that I want to make.Complicated things,everywhere, deserve a very special kind of explanation.We want to know how they came into existence and why they are so complicated.The ex- planation,as I shall argue,is likely to be broadly the same for com- plicated things everywhere in the universe;the same for us,for chimpanzees,worms,oak trees and monsters from outer space.On the other hand,it will not be the same for what I shall call 'simple'things, such as rocks,clouds,rivers,galaxies and quarks.These are the stuff of physics.Chimps and dogs and bats and cockroaches and people and worms and dandelions and bacteria and galactic aliens are the stuff of biology. The difference is one of complexity of design.Biology is the study of complicated things that give the appearance of having been designed for a purpose.Physics is the study of simple things that do not tempt us to invoke design.At first sight,man-made artefacts like computers and cars will seem to provide exceptions.They are complicated and obviously designed for a purpose,yet they are not alive,and they are made of metal and plastic rather than of flesh and blood.In this book they will be firmly treated as biological objects. The reader's reaction to this may be to ask,'Yes,but are they really biological objects?'Words are our servants,not our masters.For different purposes we find it convenient to use words in different senses.Most cookery books class lobsters as fish.Zoologists can
CHAPTER 1 EXPLAINING THE VERY IMPROBABLE We animals are the most complicated things in the known universe. The universe that we know, of course, is a tiny fragment of the actual universe. There may be yet more complicated objects than us on other planets, and some of them may already know about us. But this doesn't alter the point that I want to make. Complicated things, everywhere, deserve a very special kind of explanation. We want to know how they came into existence and why they are so complicated. The explanation, as I shall argue, is likely to be broadly the same for complicated things everywhere in the universe; the same for us, for chimpanzees, worms, oak trees and monsters from outer space. On the other hand, it will not be the same for what I shall call 'simple' things, such as rocks, clouds, rivers, galaxies and quarks. These are the stuff of physics. Chimps and dogs and bats and cockroaches and people and worms and dandelions and bacteria and galactic aliens are the stuff of biology. The difference is one of complexity of design. Biology is the study of complicated things that give the appearance of having been designed for a purpose. Physics is the study of simple things that do not tempt us to invoke design. At first sight, man-made artefacts like computers and cars will seem to provide exceptions. They are complicated and obviously designed for a purpose, yet they are not alive, and they are made of metal and plastic rather than of flesh and blood. In this book they will be firmly treated as biological objects. The reader's reaction to this may be to ask, 'Yes, but are they really biological objects?' Words are our servants, not our masters. For different purposes we find it convenient to use words in different senses. Most cookery books class lobsters as fish. Zoologists can