The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal about Aliens – and Ourselves
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- Create Date：2021-07-24 09:51:15
- Update Date：2025-09-06
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- Author：Arik Kershenbaum
- ISBN：0241986842
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Summary
A Times/Sunday Times Book of the Year
DISCOVER HOW LIFE REALLY WORKS - ON EARTH AND IN SPACE
'A wonderfully insightful sidelong look at Earthly biology' Richard Dawkins
'Crawls with curious facts' Sunday Times
_________________________
We are unprepared for the greatest discovery of modern science。 Scientists are confident that there is alien life across the universe yet we have not moved beyond our perception of 'aliens' as Hollywood stereotypes。 The time has come to abandon our fixation on alien monsters and place our expectations on solid scientific footing。
Using his own expert understanding of life on Earth and Darwin's theory of evolution - which applies throughout the universe - Cambridge zoologist Dr Arik Kershenbaum explains what alien life must be like。 This is the story of how life really works， on Earth and in space。
_________________________
'An entertaining， eye-opening and， above all， a hopeful view of what - or who - might be out there in the cosmos' Philip Ball， author of Nature's Patterns
'A fascinating insight into the deepest of questions: what might an alien actually look like' Lewis Dartnell， author of Origins
'If you don't want to be surprised by extraterrestrial life， look no further than this lively overview of the laws of evolution that have produced life on earth' Frans de Waal， author of Mama's Last Hug
DISCOVER HOW LIFE REALLY WORKS - ON EARTH AND IN SPACE
'A wonderfully insightful sidelong look at Earthly biology' Richard Dawkins
'Crawls with curious facts' Sunday Times
_________________________
We are unprepared for the greatest discovery of modern science。 Scientists are confident that there is alien life across the universe yet we have not moved beyond our perception of 'aliens' as Hollywood stereotypes。 The time has come to abandon our fixation on alien monsters and place our expectations on solid scientific footing。
Using his own expert understanding of life on Earth and Darwin's theory of evolution - which applies throughout the universe - Cambridge zoologist Dr Arik Kershenbaum explains what alien life must be like。 This is the story of how life really works， on Earth and in space。
_________________________
'An entertaining， eye-opening and， above all， a hopeful view of what - or who - might be out there in the cosmos' Philip Ball， author of Nature's Patterns
'A fascinating insight into the deepest of questions: what might an alien actually look like' Lewis Dartnell， author of Origins
'If you don't want to be surprised by extraterrestrial life， look no further than this lively overview of the laws of evolution that have produced life on earth' Frans de Waal， author of Mama's Last Hug
Reviews
rin
，
this book is basically zoology and anthropology 101 which is honestly pretty cool for anyone interested because the writing is easy， funny， yet to the point but as someone interested in biology， there were barely new revelations for me
Madhulika Liddle
，
In essence， a speculation on what intelligent life on other planets might be like。 Not whether it would have four legs or two or none or whether it would be feathered， furred， scaly or naked—not so much the look of it， but its behaviour。 How it might move， how it might communicate， whether or not it would be social， and so on。 Kershenbaum uses examples from a wide array of terrestrial living beings （including humans） to show how the environment shapes living creatures and their evolution， and th In essence， a speculation on what intelligent life on other planets might be like。 Not whether it would have four legs or two or none or whether it would be feathered， furred， scaly or naked—not so much the look of it， but its behaviour。 How it might move， how it might communicate， whether or not it would be social， and so on。 Kershenbaum uses examples from a wide array of terrestrial living beings （including humans） to show how the environment shapes living creatures and their evolution， and therefore how an environment like （or unlike） our planet may harbour life like—or unlike—that of Earth。 I found this book fascinating， insightful， and thought-provoking。 While it is about the possibility of intelligent life on other planets， it is equally a book about life on this planet， and how it is affected by various factors。 Besides the zoology （which is Kershenbaum’s main area of work）， he also draws on mathematics， physics， anthropology， and a host of other disciplines to explain his arguments。 I learnt a lot here， and a good bit of it actually wasn’t just about whether aliens might be little green men。 Or Mr Spock。 Kershenbaum is extremely readable， often witty， and the book has loads of examples （including photographs and illustrations） to explain points。 He also provides a useful annotated list of reference material and other resources， even （and I am so grateful to him for this） specifying which works are more technical， and which are more suitable for the lay reader。 A superb book， and one I’d recommend for anybody who is interested in zoology and/or astrobiology。 Or who just plain wonders if there really could be an ET out there。 。。。more
David Palmer
，
Very good book， informative and interesting。 But a warning might be necessary， to judge by the dissatisfactions of other Goodreads reviewers: the author is not interested in speculating about alternative biochemistries such as silicon-based lifeforms; nor is he particularly interested in the forms aliens might take， because body shapes like alternative biochemistries can't be predicted， being contingent upon circumstances particular to each planet。 His focus is on how aliens might act， because t Very good book， informative and interesting。 But a warning might be necessary， to judge by the dissatisfactions of other Goodreads reviewers: the author is not interested in speculating about alternative biochemistries such as silicon-based lifeforms; nor is he particularly interested in the forms aliens might take， because body shapes like alternative biochemistries can't be predicted， being contingent upon circumstances particular to each planet。 His focus is on how aliens might act， because this will be contingent upon universal laws。The author's view is that "Life follows rules。 Understanding those rules leads us to understand life everywhere。" So his speculations are based on the presumably universal application of the laws of physics （which govern the forms and movements of bodies）， the laws of natural selection （which govern the development of life）， game theory （which applies to social groupings）， and the need for energy。 Alien species will be directed by them just as we are。 He is encouraged in this by how often the same solutions to physical limitations have evolved multiple times on Earth （for example the different kinds of eyes， or the wings of birds， bats， insects and fish） suggesting they should also have evolved on other worlds， at least in Earthlike environments， though perhaps in different forms。In the end， this is a book about life on earth， with particular emphases on intelligence （including AI， which provides interesting reflections on evolution） and communication （the author is a zoologist specialising in animal communication）， and as such it is a very good introduction。 Then he uses what is known of life on Earth to speculate about how similar to life here life forms might be on other worlds。Some Goodreads reviewers have complained about his style of writing， but I suspect they haven't read many science books， for I found his writing to be clear and engaging。 You don't have to work hard to follow him。 Nor do you have to agree with him。 His stated aim is to encourage readers to draw their own conclusions - to think about things they may not have thought about before， or to think about them in new ways - and in this I believe he succeeds。There is also an excellent 'Further Reading' list， which includes science fiction （he is a fan of 'Star Trek: the Next Generation'）， so this is a good， readable introduction to both zoology and astrobiology， a mix of fact and stimulating speculation。 。。。more
Aadesh
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I don't know what we can say about aliens after reading this book but I got a lots of insights about the gray lines between living and non-living， what makes us humans， how the evolutionary landscape works and natural selection is our friend。 I don't know what we can say about aliens after reading this book but I got a lots of insights about the gray lines between living and non-living， what makes us humans， how the evolutionary landscape works and natural selection is our friend。 。。。more
Minervas Owl
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The book is not driven by sci-fi fans' wish to know what aliens look like， especially "whether or not they are green。" Instead， hidden behind the book's title， the author has the ambition to explore what any life will be like。 Whether you will like this book or not depend on whether you'd like this agenda。 For me， it was a pleasant journey。What I like the most about the book is that it knits together research from multiple disciplines such as astrology， history of life， physics of movement and The book is not driven by sci-fi fans' wish to know what aliens look like， especially "whether or not they are green。" Instead， hidden behind the book's title， the author has the ambition to explore what any life will be like。 Whether you will like this book or not depend on whether you'd like this agenda。 For me， it was a pleasant journey。What I like the most about the book is that it knits together research from multiple disciplines such as astrology， history of life， physics of movement and senses， evolutionary developmental biology， universal grammar， super-intelligent AI， and many others。 For interested readers， Arik Kershenbaum provides a well-annotated Further Reading section （available in its kindle but not the audiobook version）。 As a result， the book can serve as a primer for many scientific fields。Lastly， the narrator of the audiobook did an excellent job via the mastery of cadence。A few interesting tidbits:• Seal's body mass is lighter than water， making it easier for them to go up than to go down。 Its world is upside-down。• Dolphin's brain is closer to the bat's brain than the human brain because both dolphins and bats use the ultrasound sonar。• A lot of fungi have possibly thousands of sexes。Quote:"So many of the excellent natural history programmes on television are about showing us the diversity of life， but remarkably little about the unifying features of life。" 。。。more
Tasha
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1。 I'm proud of myself for finishing this I usually struggle with non fiction that isn't memoirs and I actually managed to finish this！ 2。 Really enjoyable and well explained。 I do however have a Bsc in general biology so I found it easier to grasp some concepts as I was already familiar with them （like game theory and kin selection for instance）。 However， the way the author talks about the more complex concepts leads me to believe that having even just a basic intro to them is enough， if needed 1。 I'm proud of myself for finishing this I usually struggle with non fiction that isn't memoirs and I actually managed to finish this！ 2。 Really enjoyable and well explained。 I do however have a Bsc in general biology so I found it easier to grasp some concepts as I was already familiar with them （like game theory and kin selection for instance）。 However， the way the author talks about the more complex concepts leads me to believe that having even just a basic intro to them is enough， if needed at all （and by basic I mean a quick Wikipedia read/YouTube video watch， not a whole degree lmao）。 I really enjoyed how the points are put forward and the structure makes sense - the book flows well from point to point with little repetition （only when necessary to link points together）。 I also found that the way the author approaches the subject to be very sensible and plausible and unlike what I expected！ Would definitely recommend to others。 3。 I docked off a star because whilst it is understandable it is very dense as the author tries to cover very many aspects and concepts in very few pages （comparatively） - however there are references for everything of books and articles and TV shows and films that go more in depth and probably explain the scope of the concepts covered "better" （as in: in more detail）。 It's very much an "exposé" of what we actually know and how we can extrapolate that more than a hard "this is what we'll find" which I enjoy as well because I share the opinion that this outlook is how we'll ever find anything anyway。 TL;DR: it's well-written， well structured （if a bit dense at times） and probably requires a little bit of background knowledge on evolutionary theory （kin selection & game theory being maybe the most important though chances are I've definitely missed others） but accessible and very interesting！！ 。。。more
Lily M
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The zoology part of the book （which is everything except for the last two chapters） was absolutely fascinating。 The author should have stopped there as his AI and philosophical musings towards the end were tedious。
The Inquisitive Biologist
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Can we predict what alien life will be like？ The Zoologist's Guide to the Galaxy is a spine-tingling dive into the lessons that evolution holds for astrobiology。 See my full review at https://inquisitivebiologist。com/2021。。。 Can we predict what alien life will be like？ The Zoologist's Guide to the Galaxy is a spine-tingling dive into the lessons that evolution holds for astrobiology。 See my full review at https://inquisitivebiologist。com/2021。。。 。。。more
Chengzhi Wu Li
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fascinating
Sydney Doidge
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This book was very enjoyable。 I loved learning about how what we know about Earth means we may be able to learn about extraterrestrial life as well！ Not in DNA but being informed by form， function， communication and how the fundamentals of evolution will remain the same。 I came away with more appreciation for earth and for life， and how incredibly tenacious life is！
CKHaught
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This was a decent look at the subject of the evolution of life beyond earth， but was by and large an introductory look at various principles underlying life on earth with very little actual consideration of how those principles might remain consistent or vary in conditions not like our own。 Overall， like most popularly intended astrobiology books I've read， I was disappointed to find that The Zoologist's Guide to the Galaxy wasn't as deep， complex or exploratory as I hoped， but most of what it c This was a decent look at the subject of the evolution of life beyond earth， but was by and large an introductory look at various principles underlying life on earth with very little actual consideration of how those principles might remain consistent or vary in conditions not like our own。 Overall， like most popularly intended astrobiology books I've read， I was disappointed to find that The Zoologist's Guide to the Galaxy wasn't as deep， complex or exploratory as I hoped， but most of what it covered was sound and it did provide extra angles for consideration。With regards to the subject of universal physical characteristics， the only real subject that he delved into was mobility， on land， in air or water and the impact of mobility on bilateral symmetry。 He didn't follow this very deeply though， and little or no mention or appraisal of cephalization， notocords， one way guts or other prominent physiological characteristics of terrestrial animals。 Likewise， he explicitly declined to speculate on the evolution of sex， or examine its variation on earth。 I did at least find his consideration of the possible evolution of primary forms of communication other than sound， and under what conditions sound-based communication is or is not ideal， interesting。 Beyond physiology， he spent a lot of time on sociological factors behind animal behavior and intelligence， and I did find his chapter on language particularly interesting。 。。。more
Pat MacEwen
，
An interesting look at life as we know it and how evolution has shaped it here， with a view toward which laws are likely to be universal。 Cambridge zoologist Dr Arik Kershenbaum explains what alien life must be like: how these creatures will move， socialize and communicate。 And while I see his point in most respects， that word 'must' is a step too far。 Based on a sample size of one， and that one world now obviously NOT all that typical of said galaxy， I found that assertion arrogant。 Even as far An interesting look at life as we know it and how evolution has shaped it here， with a view toward which laws are likely to be universal。 Cambridge zoologist Dr Arik Kershenbaum explains what alien life must be like: how these creatures will move， socialize and communicate。 And while I see his point in most respects， that word 'must' is a step too far。 Based on a sample size of one， and that one world now obviously NOT all that typical of said galaxy， I found that assertion arrogant。 Even as far as life as we know it goes， too many exceptions were overlooked for my taste。 There is， for example， very little mention of extremophiles even in terms of nutrition。 But we already know of some terrestrial life forms that can 'eat' certain metals， or even radiation itself， like that fungus in Chernobyl。 I found his discussion of intelligence and language fascinating， though again there is that tinge of arrogance and a failure to bring up certain exceptions to his rules。 There was a very good section on AI， but somehow no mention at all of cyborgs as a melding of the organic and the technological， which is already happening at the simplest levels with neural interfaces and prosthetics。 And there is no notice taken of dimensionless biology， which looks at ratios across many phyla to determine where boundaries lie on things like gender change。 So I'm going to call this one a good start， and pretty good reading， but still a bit wide of the mark。 。。。more
Carl Holmes
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Science and humor in one？ Say it isn't so！ This is an excellent read on what makes life on Earth unique， but also how they may be at work in Alien life should it be out there evolving。 A very accessible read， and one with copious links to more in depth reading should you desire to do so。 Science and humor in one？ Say it isn't so！ This is an excellent read on what makes life on Earth unique， but also how they may be at work in Alien life should it be out there evolving。 A very accessible read， and one with copious links to more in depth reading should you desire to do so。 。。。more
Michael Norwitz
，
The author seeks to derive some conclusions about the possible forms of alien life， though a lens of natural selection， and argues that despite great potential differences， alien life forms would have been subject to the same natural stressors and thus be understandable。The argument isn't implausible， although the latter part of the book devolves to philosophical meanderings about the meaning of language and culture， which I have seen discussed more profoundly elsewhere， and my attention started The author seeks to derive some conclusions about the possible forms of alien life， though a lens of natural selection， and argues that despite great potential differences， alien life forms would have been subject to the same natural stressors and thus be understandable。The argument isn't implausible， although the latter part of the book devolves to philosophical meanderings about the meaning of language and culture， which I have seen discussed more profoundly elsewhere， and my attention started to wander。 。。。more
Joni
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Very disappointing。 The author could have written his entire thesis in 20 pages。 He barely touched possible conditions on other planets。
Mandy
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The author raises many compelling questions and possible answers。 Not all theories and suggestions follow the rules put forth by the author， but all ideas are thought-provoking and certainly possible given what we know。 General knowledge and cultural examples are included band make the text easily understood。 Further reading is suggested throughout for readers eager to learn more。
Edward ott
，
Nothing definite but maybe like this。 Excellent book。
Annarella
，
An excellent informative book that made me learn a lot and fascinated me。The author is an excellent storyteller and populizer of science。 This is not an easy read but I found it very informative and found the theories about alien life very interesting。There's plenty of books about alien life but it's the first I read that is based on sound scientific theories。It's not a book you read in one afternoon but it's surely a book that will keep you turning pages。Highly recommended。Many thanks to the pu An excellent informative book that made me learn a lot and fascinated me。The author is an excellent storyteller and populizer of science。 This is not an easy read but I found it very informative and found the theories about alien life very interesting。There's plenty of books about alien life but it's the first I read that is based on sound scientific theories。It's not a book you read in one afternoon but it's surely a book that will keep you turning pages。Highly recommended。Many thanks to the publisher and Netgalley for this ARC， all opinions are mine 。。。more
Zeb
，
The start felt a bit condescending but once it reached the chapters on communication it managed to hit its stride。
Cheryl
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“We can talk about what aliens are like， because the rules of evolution are similar on all planets。 More than that， we observe on Earth the ubiquity of convergent evolution， even between the most distantly related organisms， and conclude that these organisms would also converge in their functions if they lived on different planets。 Similar solutions will arise multiple times because we live in a universe where not everything is possible。 If we see， as appears to be the case on Earth， that not al “We can talk about what aliens are like， because the rules of evolution are similar on all planets。 More than that， we observe on Earth the ubiquity of convergent evolution， even between the most distantly related organisms， and conclude that these organisms would also converge in their functions if they lived on different planets。 Similar solutions will arise multiple times because we live in a universe where not everything is possible。 If we see， as appears to be the case on Earth， that not all of the possibilities are exploited， it may be because some solutions are simply not available; perhaps they are impractical， inefficient or physically impossible: famously， for example， no animals have evolved wheels。 As Conway Morris says， ‘We live in a constrained world， where all may not be possible。’”Mind blown。 Wide open。 In love。 With this book。 Maybe a little dense and dry in places， but overall well written and he had me at ‘similar solutions will arise multiple times because we live in a universe where everything is not possible。’ There are reasons why things are the way they are， and why we don’t have blue tulips or people with gills， or why we have a limited， finite number of years to live。 I highly recommend this book for anyone who has ever pondered what aliens from other solar systems might be like and you don’t have to be huge sci-fi fan to appreciate his analysis of some of the ways pop culture has portrayed them。 We can be sure that， throughout the universe， life will require at least two things: energy and space。 Energy， because the laws of physics state that without a constant input of energy， systems decay and become disordered – the opposite of life。 Space， because two organisms take up more space than one， and reproduction is central to natural selection – the only mechanism we know of for complexity to arise on its own。 Eventually， there will be competition for energy and space。 Animals – creatures that move to compete for those scarce resources – are virtually inevitable。When dealing with the unknown， there are indeed good reasons for caution。 But there are also reasons for optimism; we just need to be careful to choose those laws of biology that are truly universal， in the same way that the laws of physics are universal。 The Earth is unlikely to be so exceptional that the rules here are different to every other planet。 Lucretius， the Roman philosopher who died in c。 55 bce， commented， ‘Nature is not unique to the visible world。’ Exoplanets have ‘nature’ as well， even if we’ve never seen them。 We want to derive a set of rules for life， in the same way that physicists derive rules for planets and stars。 If those biological rules are universal rules， they will work as well on another planet as the law of gravity。 What then are these universal laws of biology， using which we can make confident predictions about life on other planets？ The first and most important law is that complex life evolves by natural selection。Is it even true that language has evolved only once on Earth？ Is language evolving right now in some species？ And could more than one linguistic species coexist together on one planet？Since the 1960s， scientists have suggested that mathematics is a universal language， something inevitably shared between us and every alien civilization。 The laws of mathematics are， after all， truly universal。 If we try to communicate using these laws， then we are guaranteed at the very least not to be talking nonsense。 A triangle has three sides both here， and on Alpha Centauri。There is something appealing about the idea that we can broadcast abstract mathematical concepts， in the knowledge that whatever our differences in language or body form， whether we live on land or in water or in liquid methane， whether we are the size of humans， fleas or planets， whether we see with sight or sound or electric fields – there is no doubt that these mathematical principles apply to us all。 This mathematics， therefore， would be instantly recognized by another species as a sign that intelligent life exists elsewhere in the universe。But we often， and reasonably， assume that those aliens with whom we can expect to have a conversation will be more technologically advanced than us。 It has only been just over 100 years since the first radio transmission made by our species; we are absolutely in the infancy of our technological development， and that makes it exceptionally likely that any aliens we encounter will be more advanced than us。 They could be older than us or younger than us， but if we were to encounter an alien civilization at some random point in their history， there is only a tiny chance that we would happen to stumble across them in those first 100 years since they discovered radio。 In the face of civilizations that could last millions of years， the chances of us being the smart kids on the block are minuscule。Even if we could live forever， would we？ Is it even evolutionarily feasible？ Why don’t any natural organisms live forever？ True， they lack the foresight and the technology of artificial creations， but they have been around for a lot longer。 As it turns out， there are good reasons why immortality is a bad idea。 Evolutionary theory suggests that death is not a parochial feature of life on Earth。 Technologically sophisticated alien civilizations aside， animals on other planets will die。 Death is essential for evolution， and – at least until technology can be invented – evolution is the only way that complex animals can arise from simple。 Firstly， and most obviously， if no one died， we would run out of space。 Secondly， the world is full of changes。 No matter how smart we parents are， no matter how much we know （and we really do believe that we know）， sooner or later， the world will change beneath our feet， and presto: our children are teaching us how to use our smartphones， and how not to embarrass ourselves on Snapchat。 Thirdly， and most importantly， life is full of trade-offs。 It is an irreconcilable feature of the universe that you can’t have all you want of everything。 Immortality comes with costs。 Even for a radical， technological， non-Darwinian life form， so many of the principles that we use to understand the evolution of life on Earth still apply， and so it is unlikely that they would design themselves to live forever。Throughout the ages， people have imagined aliens either as exaggerated humans or exaggerated Earthling animals – perhaps giant spiders or worms， designed to induce nightmares。 The unknown and the dark are as frightening to us as they were to our ancestors before the invention of electric lights， and we fear that ‘out there’ may be animals and demons lying in wait。 But how aliens act is much easier to predict than their appearance。 Looks are more prone to accidents of evolution and quirks of embryological development; behaviour is a more fundamental response to the environment。 Each chapter in this book is about some feature of animal behaviour on Earth that is not unique to Earth – that can’t be unique to Earth。The question of how we will react as a species when we first discover that life exists on other planets is one that has not been sufficiently considered。* Will there be mass hysteria and looting？ Religious fundamentalism， or a mass abandonment of religion？ Or perhaps， according to the sixties hit ‘Aquarius’， ‘Then peace will guide the planets， and love will steer the stars’？ We cannot be ill served by being prepared。If we live in cooperative societies and they do as well， then it is no small feat that we can identify the common evolutionary origin of our sociality。 And maybe， just maybe， we will be able to use the term ‘humanity’ to mean something a little more broad， and more significant， than just the descendants of a group of apes that wandered across the grasslands of a tiny corner of one continent on a tiny planet in a corner of just one galaxy among billions。Despite the apparent similarities between dolphins and ichthyosaurs， these two species are as unrelated as a human and a newt。 Form – what an animal looks like and behaves like – is inextricably tied to function – how the animal makes its living， gathers energy and reproduces。 This connection is the key to how we can know what aliens are like， without descending into fictional speculation。Stephen Hawking said that we could， in fact， know the mind of God， but only by understanding all the laws of physics in their entirety。* We are quite a long way from that goal。At its simplest level， natural selection is easy to understand。 Beneficial traits accumulate。 Some new features will survive， other innovations will not， but good ideas developed by previous generations are not forgotten。Imagine randomly choosing a string of twenty letters， say SDFLKJFGOSDIFHGSOFGH。 The chances of arriving at a particular sequence， say， ‘The Blind Watchmaker’， are astronomically small: actually， one in 42 billion billion billion。* But if each time you make some random changes to the sequence above， you keep changes that match the sequence we’re looking for， ‘The Blind Watchmaker’， the result is completely different。 Good innovations – say， changing the initial ‘S’ （which isn’t in the target sequence） for a ‘T’ Remarkably， using this ‘selection’ approach， the correct sequence emerges after about just 540 attempts， an improvement by a factor of about 80 million billion billion！*All the competing ideas that have been proposed to explain the origin of complex life are very much descriptive， rather than explanatory。 British philosopher Bertrand Russell said， ‘I like mathematics largely because it is not human and has nothing particular to do with this planet or with the whole accidental universe – because， like Spinoza’s God， it won’t love us in return。’If time is unlimited， then we must rethink the nature of the origin of life。 But the scientific community is confident that the universe did indeed have a beginning， and so life too must have had a finite beginning – and life must have developed and diversified from that beginning。 Natural selection is our universal explanation for this process。Sexually reproducing animals （and plants） are ubiquitous on Earth， and are more diverse in both their form and function than the rather uncomplicated asexual bacteria。 Strawberry plants mostly reproduce asexually， sending out runners that spawn new plants， clones of the original， and rarely do daughter plants sprout from seeds。 But the delicious strawberry fruits （seeds and all） are the product of sexual reproduction。 No explanation for the evolution of sex is universally accepted。 But whatever the reason， most scientists would agree that sexual reproduction was essential for the diversity of life on Earth。 Even more than that， it seems unlikely that life on Earth would have reached anything like the complexity that it has， were it not for sexual reproduction。We can talk about what aliens are like， because the rules of evolution are similar on all planets。 More than that， we observe on Earth the ubiquity of convergent evolution， even between the most distantly related organisms， and conclude that these organisms would also converge in their functions if they lived on different planets。 Similar solutions will arise multiple times because we live in a universe where not everything is possible。*We have an instinctive understanding that we share something in common with all animals – we’re not sure what that is， and it certainly isn’t as simple as physical appearance， but we know that you and I， and the spider and the earthworm， all are part of the same group that we call ‘animals’。 Can we – the general public as well as the scientific community – agree on what animals are？ And even if we can agree on what animals are on this planet， would that definition apply to animals on other worlds？ Agreeing on what defines an animal is something with which humanity will have to come to terms sooner or later。 We have a bond of identity with animals – whatever they are – and that affects our attitudes towards them， both ethical and social。 Can it be as simple as that？ Animals move， plants do not。 The ability to move underlies all the other developments I will discuss: cooperation， sociality and – especially – intelligence。However， a lack of competition does not bode well for evolution – as in those circumstances there is no advantage to innovation， and there are no real problems that need to be solved。 Some organisms fared better than others and reproduced more， but everyone had a pretty easy time and life forms were pretty simple。 Life began about 3，800 million years ago， but for the first 3，200 million years， no one ate anything other than sunlight。At some point， an organism existed that was the common ancestor to all modern animals （and also， bizarrely， happened to be the ancestor to fungi）。 This creature was single-celled and propelled itself with a tail， rather like a sperm cell。 It bears the fantastic name of opisthokont – well worthy of a creature with such a foundational role as the ancestor of all animals。 Opisthokonts appeared around 1，300 million years ago， long， long before Ediacaran times。More likely， the climate changed and the endless free lunch was no more。 One creature began to get energy， not from the sun or from the hot volcanic waters， but from ingesting other living organisms。 In the biblical story Adam and Eve， and all the other creatures in the Garden of Eden， were vegetarians， living the easy life， until they were thrown out of the Garden; and so it was in reality。 Once predation became a thing， evolution went into overdrive: those organisms that didn’t adapt were lunch – literally。 All kinds of defensive and offensive traits began to appear: protective spines， etc。We can be sure that， throughout the universe， life will require at least two things: energy and space。 Energy， because the laws of physics state that without a constant input of energy， systems decay and become disordered – the opposite of life。 Space， because two organisms take up more space than one， and reproduction is central to natural selection – the only mechanism we know of for complexity to arise on its own。 Eventually， there will be competition for energy and space。 Animals – creatures that move to compete for those scarce resources – are virtually inevitable。Evolution often seems to come up with similar solutions to the same problem。Underground oceans like those on Saturn’s moon Enceladus receive no sunlight， but there is energy aplenty， partly from the radioactive decay of elements in the planet’s core， but also from the friction of the tides – the huge force of the gravity from Saturn pulling the rock and water backwards and forwards。For a complete ecosystem to develop around such aerial plankton， including large planktonic-feeding sky-whales， organisms must evolve to be larger and larger， without simultaneously falling out of the sky。 Neutral buoyancy is easy to maintain in liquid。But crucially， human legs are built completely differently from spider legs。 Arthropods have a rigid exoskeleton， with their soft bits inside; vertebrates have rigid bones， with soft tissues outside。 The two evolutionary pathways came up with functionally similar solutions to the problems of moving at a surface， using completely different mechanisms。 Which is better？ Neither， nor does it matter。Each innovation was based on， and constrained by， the details of the body plan of their ancestors。Why do we have so many senses？ Is it really necessary that we （and other animals） can simultaneously see and hear what is going on around us？ There are some good reasons to think that using multiple modalities to sense the world and also to communicate gives animals a robustness in the face of changes in the conditions around them。Are we unusual in using sound to communicate， or is there something special about sound itself that makes it almost inevitable as a signalling modality？ Is the fact that we seem to be surrounded by acoustic signals just a peculiarity of the conditions on our planet？ Or might there be something special about sound waves that makes them particularly suitable for being crafted as communication – and even into a language？Sound has a very important property that （on our planet） undoubtedly propelled it to be the dominant modality for communication。 Sound travels around things。 No matter that the pigeon is hidden in the leaves or the cricket in the grass， the sound reaches us anyway。 Light is blocked by most solid objects; sound goes around them。Anyway， on Earth， life means electricity。 If all life generates electricity， then sooner or later some life form will evolve the ability to detect electricity so that they can hunt down other organisms and gobble them up。 Electroreception， or the ability to detect electric fields， is widespread among many different species of fish， including sharks， but is also found in amphibians， like salamanders， and， bizarrely， in some mammals， like duck-billed platypuses， which hunt out their prey by detecting the electric signs of life penetrating through their muddy environment。We want to know what Einstein， Mozart and every one of us have in common， and how that evolved from our ancestors who didn’t possess ‘that’， but possessed some other kind of intelligence – about which we also want to know。 Can we provide a way of looking at intelligence that simultaneously applies to all creatures， from sponges to humans， capturing a process that is general enough to apply on other planets as well？ In a famous essay， the philosopher Thomas Nagel proposed that it is not enough to try to imagine how a bat perceives the world。* At the very best， we could understand only a human’s translation of a bat’s perceptual experiences。 The ‘batness’ of the experience would be completely beyond us。 。。。more
Richard
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Seeing life in the galaxy through a mirror。
William Bennett
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I enjoyed the thought experiment of trying to hypothesize what extraterrestrial life would look like， based on earthling patterns。 It was fascinating to consider that life， regardless of its origin， will likely follow the same rules or conform to the same observations scientists make on Earth。 I don’t agree with all the author’s conclusions， but I felt the book to be mind-expanding。 The author successfully made the subject accessible。 I would have liked it to be a bit more engaging beyond a spri I enjoyed the thought experiment of trying to hypothesize what extraterrestrial life would look like， based on earthling patterns。 It was fascinating to consider that life， regardless of its origin， will likely follow the same rules or conform to the same observations scientists make on Earth。 I don’t agree with all the author’s conclusions， but I felt the book to be mind-expanding。 The author successfully made the subject accessible。 I would have liked it to be a bit more engaging beyond a sprinkling of pop culture references （which I enjoyed）。 。。。more
Alb85
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Forse l’unica possibilità di studiare davvero la vita aliena è grazie alla teoria dell’evoluzione。 Comprendendo i vincoli posti alla vita e applicandoli alle condizioni fisiche di altri pianeti， possiamo avvicinarci il più possibile a essere «zoologi alieni»。 Arik Kershenbaum。Ho trovato questo libro troppo “pop-science”。 L’autore non approfondisce i concetti presentati e questo rende il libro troppo superficiale。Il messaggio è che la selezione naturale dovrebbe governare non solo la vita nel nos Forse l’unica possibilità di studiare davvero la vita aliena è grazie alla teoria dell’evoluzione。 Comprendendo i vincoli posti alla vita e applicandoli alle condizioni fisiche di altri pianeti， possiamo avvicinarci il più possibile a essere «zoologi alieni»。 Arik Kershenbaum。Ho trovato questo libro troppo “pop-science”。 L’autore non approfondisce i concetti presentati e questo rende il libro troppo superficiale。Il messaggio è che la selezione naturale dovrebbe governare non solo la vita nel nostro pianeta ma anche la vita in tutto l’universo “la selezione naturale è inevitabile， anche in contesti diversi dalla biologia come programmi informatici， memi su Internet， credenze religiose ecc。， ma lo è soprattutto nei sistemi biologici。”Nel libro non si parla vi forme di vita in generale ma di “animali”。 Secondo la tesi del libro la vita dovrebbe portare ovunque alla formazione di animali con comportamenti comuni quali movimento， comunicazione， e cooperazione。Tutte le ipotesi vengono formulate a partire dallo studio della vita sulla Terra， in particolare studiando l’«evoluzione convergente»: “sappiamo che il volo muscolare è comparso almeno quattro volte sulla Terra。 Occhi come i nostri， dotati di un cristallino grande， si sono evoluti almeno sei volte。 La capacità di generare un campo elettrico emesso dal corpo si è evoluta almeno lo stesso numero di volte。 La nascita della prole dal corpo materno sembra essersi evoluta （in maniera indipendente） oltre cento volte。 Persino la fotosintesi， base di tutta la vita sulla Terra， si è probabilmente evoluta in almeno trentuno linee separate di discendenza。"Ho trovato interessante in confronto （simulato al computer） tra evoluzione darwiniana che ha terreno fertile in ambienti mutevoli （come sulla Terra） e l’evoluzione lamarckiana， più efficace in ambienti che non cambiano molto。 In sintesi， mi aspettavo qualcosa di più。Spunti interessanti:-t“L’evoluzione richiede pressione， competizione， scarsità。”-tCon l’eccezione notevole delle spugne， delle meduse， degli ctenofori e dei coralli， quasi tutti gli animali moderni hanno un lato destro e uno sinistro; ciò riguarda oltre il 99% delle specie oggi viventi。 Nessun animale privo di questa simmetria può competere con la velocità e l’efficienza energetica delle appendici situate a destra e a sinistra， che si tratti di zampe o semplici lembi di pelle。-tÈ straordinario che probabilmente il paesaggio alieno ci sembrerà riconoscibile all’istante， grazie alla sola maniera in cui i suoi abitanti si muovono nel loro mondo。-tL’idea di un linguaggio basato sugli odori sembrerà forse ridicola ma potrebbe essere un errore: Sappiamo che nel nostro naso， piuttosto scarso， si trovano recettori per circa 400 sostanze chimiche diverse; i cani ne hanno 800 e i topi riescono addirittura a distinguere 1200 stimoli。 Ciò significa che in teoria siamo capaci di rilevare almeno 10120 combinazioni chimiche diverse， di gran lunga più numerose di tutti gli atomi dell’universo。-tL’elettroricezione， cioè la capacità di rilevare i campi elettrici， è comune tra varie specie di pesci， inclusi gli squali， ma si trova anche negli anfibi come le salamandre e curiosamente in alcuni mammiferi， come gli ornitorinchi， animali con un becco d’anatra che individuano le prede rilevando i segnali elettrici penetrati nel loro ambiente fangoso。-tSembrano esserci due motivi per cui sulla Terra scarseggiano le creature con segnali elettrici sofisticati。 In primo luogo， è un sistema molto dispendioso da evolvere e da mantenere。 -tè stato l’economista matematico John Nash a elaborare la teoria dei giochi， che descrive le basi su cui la cooperazione animale a volte si verifica e a volte no。 Tramite una struttura matematica di meravigliosa semplicità， la teoria dei giochi prevede come qualcuno （animale， umano o alieno） si comporterà a lungo termine， se anche altri cercano di ottenere il miglior tornaconto individuale。-tPropongo questa definizione evolutiva di comunicazione: Segnale che， prodotto da un animale e ricevuto da un altro， modifica il comportamento del destinatario in modo da aumentare l’idoneità evolutiva del mittente。-tScienziati come Noam Chomsky hanno affermato che， oltre a condividere alcuni elementi （come nomi e verbi）， tutte le lingue di fatto li combinano in maniera analoga， seguendo regole ben definite che si possono rappresentare matematicamente。-tFacendo i conti si scopre che， proprio a metà strada fra il caso del 20% per ciascuna delle lettere （casualità）， e il 96% contro l’1% （banalità）， si trova la legge di Zipf。 Questo caso equilibrato prevedrebbe che la A abbia una frequenza doppia della B， tripla rispetto alla C e così via。 Per un segnale composto soltanto da queste cinque lettere， troviamo che ciò corrisponde approssimativamente a un 44% di A， 22% di B， 14% di C， 11% di D e 9% di E。 Sembrerebbe che queste probabilità rappresentino il modo oggettivamente equilibrato per inviare un segnale: né troppo complesso， né troppo semplice。 Secondo alcuni， è per questo che la legge di Zipf ricorre tanto spesso。 Fornisce appena la complessità sufficiente per l’informazione， ma non tanta da sopraffarci。-tSi sono create versioni al computer di mondi in evoluzione con un gran numero di creature virtuali dette «agenti»， che si contendono le risorse virtuali。 in un caso si evolvono secondo la selezione naturale （agenti «darwiniani»） e così diventano più numerosi gli agenti di maggior successo， mentre nell’altro caso （agenti «lamarckiani»） possono trasmettere la loro rete neurale appresa alla «prole»; i figli iniziano quindi la vita con le informazioni apprese dalla rete neurale dei genitori。 Se l’ambiente non varia molto， è vantaggioso poter trasmettere le proprie esperienze ai figli。 In un ambiente mutevole， invece， le carte in tavola sono diverse。 Se il mondo cambia di continuo， nascere conoscendolo già può essere uno svantaggio。 -tLupi e coyote si differenziano per l’aspetto， il comportamento， la nicchia ecologica occupata e le prede cacciate。 Sembra che non siano la stessa specie， ma possono riprodursi insieme e lo fanno。 Succede tuttora la stessa cosa per tutte le specie。 Cani e lupi non sono distinti， ma si stanno distinguendo， una generazione dopo l’altra。 。。。more
Flora Doohan
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This book is an enthusiastic dive into the kind of speculative evolution that I love。 The book was always interesting without either jumping around too much or dwelling too much on complex topics。 I felt it tied together current observations， investigations into the past， and speculations about the future in a way that was grounded and made interesting connections。 A wonderful read！
E。W。 Barnes
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Fascinating examination of evolution and what it means to be human， and how they might play out on another planet
Barney
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Hrm。 This was expansive， interesting， and well-articulated - but not really what I thought it'd be。Kershenbaum charts the many weird twists and turns life on Earth has taken and uses it loosely to identify possible commonalities between Earth life and alien life。 For instance， the fact that flight has evolved separately numerous times on Earth means we can say with a degree of certainty that flying alien animals should exist elsewhere in the Universe。But I fell victim to my own assumptions/expec Hrm。 This was expansive， interesting， and well-articulated - but not really what I thought it'd be。Kershenbaum charts the many weird twists and turns life on Earth has taken and uses it loosely to identify possible commonalities between Earth life and alien life。 For instance， the fact that flight has evolved separately numerous times on Earth means we can say with a degree of certainty that flying alien animals should exist elsewhere in the Universe。But I fell victim to my own assumptions/expectations。 I was expecting it to be more along the lines of a scientifically-backed thought experiment by a zoologist who， using real-life examples from Earth， imagines what life might look like in Titan's icy oceans， or on a tidally-locked moon， or a planet with low gravity etc。 So I ended up being a little disappointed - I want to read about giant， glowing， gliding aliens， is that too much to ask？ 。。。more
Sara
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This book was exactly 'up my alley' in terms of interest。 The author speculates on what intelligent life might look like on other planets。 He explores a variety of topics on the matter including movement， sociality， communication， intelligence。 Most of the chapters were really interesting and engaging。 I had not read about how movement and predation evolved so they were new ideas for me。 I also really enjoyed the chapters on the different types of communication that can occur between populations This book was exactly 'up my alley' in terms of interest。 The author speculates on what intelligent life might look like on other planets。 He explores a variety of topics on the matter including movement， sociality， communication， intelligence。 Most of the chapters were really interesting and engaging。 I had not read about how movement and predation evolved so they were new ideas for me。 I also really enjoyed the chapters on the different types of communication that can occur between populations and why auditory is the most likely。 Toward the end， he explores 'what is humanity' which is always a fascinating thought for me as an advocate for animal right and he rightfully points out the imperfection of the species concept。 The intelligent design idea was a fun thought experiment as he compared and contrasted the different ways life forms could evolve including the idea of programming Lamarckism into robots and its limitations。 The only chapters that dragged a bit for me were ones on signaling and language as I feel that linguistics can certainly be a bit of a dry topic。 The author is exceptionally thorough about crediting authors within the text， which is a nice way to pay homage and clearly demonstrated his love of the topic。 Pictures are relatively scant， but I don't think it takes away from the book as I found is fairly comprehensible。 Actually， I thought it did a great job in terms of accessibility- not too easy and not too dry and hard to follow。 There are some pop culture references sprinkled throughout， which I didn't mind and were not excessive。 I am not sure everyone would get all the references， but I mostly did。 Makes sense given our parallel interests。 I'll need to bookmark this author as a favorite。 This is his first book and hopefully he writes some more。 。。。more
Robby
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Interesting read。 Learned a bit， and that's what I wanted to do！ Interesting read。 Learned a bit， and that's what I wanted to do！ 。。。more
Molly
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It's written clearly in a language that is easy to understand and enjoyed reading about hypothetical life in space。 Love the science fiction references。 I have some questions I wished I could have asked as I read because this is a thought provoking book。 My main criticism of this book is how it is edited， I was pulled out of the reading by the footnotes and reference to other chapters because it just broke my flow of reading。 It's written clearly in a language that is easy to understand and enjoyed reading about hypothetical life in space。 Love the science fiction references。 I have some questions I wished I could have asked as I read because this is a thought provoking book。 My main criticism of this book is how it is edited， I was pulled out of the reading by the footnotes and reference to other chapters because it just broke my flow of reading。 。。。more
Brad
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