Our Final Hour: A Scientist’sWarning: How Terror, Error, andEnvironmental Disaster ThreatensHumankind’s Future in thisCentury – On Earth and Beyond/Our Final Century: Will the HumanRace Survive the Twenty-FirstCentury?by Martin ReesBasic Books: 2003. 256 pp. $25/William Heinemann: 2003. £17.99

Don Brownlee

I must admit I was startled when I first heardthe title of Martin Rees’ new book, Our FinalHour. Is it really possible that our end couldbe so near? Could our species become extinctless than three centuries after the publicationof Darwin’s Origin of the Species? We humanshave only just begun to understand what we are and how we fit into the cosmos. Howcould the curtain fall on us so soon? My initial shock and knee-jerk scepticism waseased, at least a bit, when I found that the UK version of this book is titled Our FinalCentury. As is the case with most apocalypticassessments, the prediction may involve afew orders of magnitude of uncertainty.

Gloom and doom is an intriguing andpopular genre but it can also be disturbing.Together with palaeontologist Peter Ward, I recently wrote The Life and Death of PlanetEarth (reviewed in Nature 422, 663; 2003). In writing the book, and in numerous talksand interviews given after its publication, we had to deal sensitively with people’s fearsof an unpleasant, albeit distant, future. As an astronomer and a palaeontologist we feelcomfortable with the premise that the Earthwill lose its plants and animals in a billionyears or less, its oceans and all life within several billion years, and ultimately becomeassimilated into the red giant Sun in about 7 billion years. We are at peace with our cos-mic fate, smugly encapsulated in the presentand well isolated from the future. But manyreaders are genuinely disturbed that thereare bad things ahead, even if they are millionsor billions of years away.

Now Martin Rees, Britain’s astronomerroyal and an author entitled to be taken veryseriously on such a weighty topic, suggests thatour end is essentially here. He wagers thathumans have a 50% probability of becomingextinct by the end of this century. Ward and I had conjectured that humans, being wily,adaptive creatures perhaps immune to futurenatural selection, might be among the last of Earth’s animals to reach extinction. Reessuggests just the opposite: that nearly all ofEarth’s large mammals may outlive us for the

simple reason that they do not have scienceand technology, and so lack the tools to dothemselves in. We cry “save the whales”, but we may be the ones who need saving.

There are some profoundly unsettlingaspects to this book. It is bad enough that theend might be near, but it is even worse thatthe cause of our demise could be science. As a scientist, I have always considered scienceto be the most successful human endeavour.The bootstrap aspect of science and the roleof nature as the ultimate arbiter of truth haveled us far. Starting with sticks, fire, flint andpottery, our ambitions to comprehend andutilize nature have led to indoor plumbing,spacecraft, the Internet, a sophisticated viewof the cosmos, and even a substantial glimpseinto the intricate workings of biology.

If Rees is right, the continual advance ofscience has been a walk to the gallows. Ourhard-earned knowledge of natural processeshas led us to the threshold of destruction.Within the next century, the ability to build designer viruses, nano-robots or evensome type of computer-instigated cyber-doom will have advanced to the point thatperhaps a single deranged individual willhave the ability to kill us all. There will alwaysbe lunatics, so if the power is there, we aredoomed. This is the fundamental thesis proposed by Rees.

The book is a shopping list of how the endmight come. It includes exotic concepts ofhow our fiddling might end the world oreven muck up the entire Universe, but the

focus is on our self-extinction. Having sur-vived predictions that the ‘electronic brain’and the robot would have taken over longago, my personal guess is that cyber-threatsand killer nanobots will never be able to taketotal control, but who knows?

The threat of specifically designed killerviruses or diseases seems more credible, andnew biological threats are sure to cause havocin the future. But can even the most deadlydesigner bugs cause total human extinction?The nastiest viruses are usually not very successful because they kill their host beforethey can be transmitted. Life is actually pretty robust, the product of the toughtaskmaster of evolution. Viruses have beenattacking bacteria in the oceans for billionsof years and, even though they outnumbertheir hosts by orders of magnitude, the viralattackers can never completely win.

In my mind, humans are nearly extinc-tion-proof unless they are exposed to globalchanges to which they cannot adapt. If ananobot, or a microbial or nuclear attack,was only 99.9999% efficient, the remainingisolated patches of humanity could live offthe largesse of the modern world for quite a while. The first serious global attacks onhumans are likely to be much less than 100% efficient. Even a minor kill-off wouldprovide quite an incentive for the survivorsto prevent future attacks.

A quite remarkable aspect of this book is that the author, a famous scientist, clearly assigns the blame for the anticipated

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A walk to the gallowsCould scientific advances be hastening the end of the world?

Virtual reality? Computing advances leave us open to the risk of cyber-doom, as in Lawnmower Man 2.

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apocalypse on science. The core of the threatis not only science but also knowledge. The book rings the alarm but provides noanswers because there are none. Scientistsare motivated by curiosity and a yearning tounderstand nature, but the real engines ofscience are business and war. Without globalcultural revolution, business, war, scienceand education will surely continue. Can wemanage the dark side of science and proveRees wrong? Only time will tell.

I highly recommend this provocative andeducational book. It is written for broadappeal and even includes a crowd-pleasingarray of references to popular culture. If wedo survive to see the twenty-second century,I hope that Martin Rees’ cautionary andalarmist book will be required high-schoolreading, a twenty-first-century analogue ofRachel Carson’s Silent Spring. I also recom-mend Future Evolution by Ward and AlexisRockman (reviewed in Nature 416, 125–126;2002), a discussion of the fate of humans thatfavours their survival but warns of direeffects on the rest of the planet’s inventory ofplants and animals. ■

Don Brownlee is in the Department of Astronomy,University of Washington, Seattle, Washington98195, USA.

Four legs bad, two legs goodLowly Origin: Where, When, andWhy Our Ancestors First Stood Upby Jonathan KingdonPrinceton University Press: 2003. 408 pp. $35, £24.95

Lorenzo Rook

Jonathan Kingdon is not only a zoologistwith a deep knowledge of African mammals,but also a fine narrator and a talented artist,so any new book by him is particularly welcome. In Lowly Origin he offers the reader a finely illustrated book on humanevolution, focusing particularly on the tran-sition from four-legged apes to two-leggedhominins.

The origin of our ability to walk on twolegs is one of the most debated subjects in anthropology. Here Kingdon attempts to explain to a wide audience, and to shed new light on, the origin and consequences of this turning point in human evolution.The book’s strength is its broad perspective,bringing ecological, palaeoenvironmentaland palaeogeographical evidence into ananalysis of our “lowly origin” (the title istaken from the last two words of Darwin’sThe Descent of Man).

Over ten chapters, Kingdon providesviews on the evolutionary trajectories of fore-limbs since Palaeozoic tetrapods, ponders the

evolutionary patterns of African hominins as driven by physical limits between geo-graphic regions (by ‘basin evolution’), anddiscusses the role of brain expansion in driving the modern diaspora. He repeatedlyrefers to “self-portraits”, both as an abstractmental exercise comparing humans andother primates or animals, and by includingillustrations of himself in comparison withother primates and humans — the exampleshown above is just one of many intriguingjuxtapositions. As a “repentant vandal”, Kingdon summarizes in the final chapter our status as the last survivors of the manybipedal African mammals that persisted untilrecent times, and offers insight into the futureof our species.

There are a few weak points, however. Insome places the ongoing debate on somecrucial issues is missing and a definite posi-tion is taken instead. For example, therecently described Sahelanthropus fossilfrom Chad is mentioned as a gorilla-like ape but is totally overlooked in the chaptersthat discuss the earliest hominin.

Another case is the origin of the Africanape–human clade (the taxonomic groupincluding Homo and his nearest living rela-tives, Pan and Gorilla). Some recent papershave argued that the European Late Mioceneapes were the ancestors of the Africanape–human clade, suggesting that hominidsleft Africa for Europe about 20 million yearsago and returned some 10 million years later.Kingdon accepts this ‘out of Africa and back’hypothesis — the Eurasian origin of his

“squatting ground ape” is a recurrent motifthroughout the first part of the book. But indoing so, he neglects the wide palaeoecologi-cal perspective that is otherwise the mainstrength of this book.

The European hominoid with the widesttemporal and geographical range is Dryo-pithecus, a large-bodied arboreal ape adapted for a diet of soft fruits. A slightlymore recent European ape is Ouranopithecus(also known as Graecopithecus), a hominoidabout the size of a female gorilla that isadapted to eating hard fruits. Dryopithecusis associated with swampy subtropical envi-ronments (from Spain to Eastern Europe),whereas Ouranopithecus (from Greece) andclose relatives from Turkey lived in ratheryounger, more open woodland.

Does the available palaeontological andpalaeoecological information support thedispersal of Dryopithecus or Ouranopithecus-like forms from Europe into Africa? The ‘out of Africa and back’ hypothesis is essen-tially based on ‘strong’ cladistic analyses (a procedure for organizing the evolution-ary relationships among taxa on the basis ofshared anatomical characters) that representDryopithecus and Ouranopithecus as beingsister taxa of the African ape–human clade.This hypothesis is favoured by some authorsbecause there was a ‘hominoid vacuum’ inAfrica between 12.5 million and 6 millionyears ago. But the large-mammal fossilrecord in Africa is relatively poor for thistime interval, so the absence of hominoidfossils cannot be taken as evidence that hominoids were not living in this area during this period.

Dryopithecus was dependent on equable,subtropical temperate forests, below-branchlocomotion and a soft-fruit diet, so it is notlikely to have moved across the more openwoodland of the southwestern Mediter-ranean during the Late Miocene. Ourano-pithecus is also an unlikely ancestor of theAfrican ape–human clade, because its teethand jaws had thick dental enamel and wereadapted for a diet of hard fruits and seeds. Assuch they were more comparable to the teethof later mid-Pliocene to early Pleistocenehominids (between 3 million and 1 millionyears ago) than to the thin-enamelled teethof the early bipedal hominin of Ethiopia orthe earliest Late Miocene hominin fromKenya or Chad.

Despite its lack of discussion of theseissues, Lowly Origin should interest a wideaudience. It will serve as supplementaryreading for researchers and graduates, butshould also be accessible to lay readers. King-don is an authority on Africa’s zoology, andhas merged his deep knowledge of mammalevolution with his love for Africa and art. ■

Lorenzo Rook is in the Department of EarthSciences and the Natural History Museum,University of Florence, via G. La Pira 4, 50121 Firenze, Italy.

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Face facts: Jonathan Kingdon highlights thesimilar expressions of humans and orang-utans.

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