book reviews Evolution rising from the grave Reactivation of a dormant message signals the dawn of a new humanity.

Darwin’s Radio In writing Darwin’s Radio, Bear treads on by punctuated equilibria. The fossil record by Greg Bear the toes of the scientific élite: “Ernst Mayr’s shows bursts of speciation and extinction Del Rey: 1999. 430 pp. $24 kids are sweating ice cubes ... Dawkins is cutting across entire fauna and flora. Yet we Michael A. Goldman beside himself.” He has mustered a cadre of seldom make the connection that vertical facts, loosely connected and ill understood. transmission of genetic information could It is the dawn of the third millennium. It may There are little happenings at the periphery occur within and among higher eukaryotic be the dawn of a new humanity. It is the great- of Mendelian genetics, at the edge of neo- species, and that clusters of transposition est scare since the bubonic plague. It mani- Darwinian theory, and what used to be events could occur in response to environ- fests itself as cold-like symptoms in pregnant beyond the realm of molecular biology. We mental signals. Bear the science fiction women, and as devastating malformations in know that bacteria contain extrachromoso- writer makes the connection for us. their fetuses. It shakes the very sequence of mal elements that transmit traits, such as Most of us believe that simple, incremen- the human genome. A cataclysm of biblical drug resistance, between individuals and tal changes in allele frequencies, driven by the proportions in the making, it is dubbed between species. We know that elements forces of genetic drift, mutation, recombina- Herod’s influenza. A hitherto-silent human exist which insert in and excise from the tion, migration and natural selection, are endogenous retrovirus has excised itself from genome, sometimes in response to environ- enough to explain evolution — from adapta- the genome and become mobile and infec- mental signals or stresses. tion to speciation, to the origin of higher tious once again. Such extraordinary magic isn’t limited to taxa. There is no compelling evidence to the SHEVA — scattered human endogenous single-celled organisms. Even before bacter- contrary, but neither is there compelling retrovirus activation — has been seen in the ial transposons, plasmids and phages were evidence in favour of the idea; we simply past. In mass graves, where men and preg- understood, Barbara McClintock had seen haven’t observed or catalogued the forces and nant women had been slaughtered, their evidence for movable elements in maize, changes that create new species. Bear fills remains tested positive for SHEVA. It was with all the prescience of Kaye Lang, Bear’s this void in our understanding with the also present in a well-preserved Neanderthal heroine. We are faced with our growing notion that radical changes in the genome, couple found in an ice cave — the woman’s knowledge of the human genome. It is brought about by mobilization of transpos- unborn child had met a violent end. The littered with the footprints of ancient able elements such as human endogenous dread disease spreading across the face of the retrotransposons, ancient retroviral infec- retroviruses, result in rapid change at the sub- Earth today had broken out aeons before, at tions and shocking, widespread rearrange- species or species level. the dawn of Homo sapiens sapiens. Renegade ments. Stephen Jay Gould and others have I’m not afraid of this concept. Bear goes a scientists would show that SHEVA was not advocated the notion that evolution occurs little further in suggesting that such change the awful disease Herod’s influenza implied. It was, rather, Darwin’s radio, conveying the message that would catapult mankind to its next step in evolution. I am not a reader of mainstream science fiction, but for years I have told incredulous students, colleagues and friends that good, and even bad, science fiction can spark public interest in and understanding of science and its implications for our society. Jurassic Park has taught a generation about the possibili- ties and impossibilities of genetic engineer- ing. Gattaca makes us think about where we’re going with human genetic screening and genetic enhancement. But Greg Bear’s novel Darwin’s Radio goes one step further. It not only gets the non-scientific reader to think about details of molecular biology such as retroviruses, it challenges busy scientists to think freely about what the disjointed discov- eries of the past few decades might really mean. And it reminds us just how closed to new ideas we can sometimes be. Bear restates the idea that science moves forward when orthodoxy is challenged. But the orthodoxy Buried in their thousands challenged must be last week’s dogma; tam- pering with today’s can be hazardous to one’s The tomb of China’s first emperor, the self- production of exquisite Chinese works of art career. This the scientists in Darwin’s Radio styled First August Emperor of Qin, is guarded found throughout history. Ten Thousand learn. The pioneering thinkers of yesterday by a terracotta army of up to 7,000 life-size and Things: Module and Mass Production in Chinese are the devoted traditionalists of today. New lifelike warriors, which were only unearthed in Art by Lothar Ledderose (Princeton University ideas enter science grudgingly. New para- 1974. This is just one example of the mass Press, $60, £38) celebrates these achievements. digms are resisted with a vengeance. © 2000 Macmillan Magazines Ltd NATURE | VOL 404 | 2 MARCH 2000 | www.nature.com 15 book reviews can occur over about a generation, an idea molecules whose sequence of chemical length of the day, the Sun’s altitude at noon, that might be a little too radical at the bonds encodes information on a nanometric and so on. As we read in the Encyclopédie, the moment. However, he does mention data scale. If we can use the DNA molecule to great inventory of the knowledge of the suggesting that fruitflies can adapt to a new carry out calculations in ways that were Enlightenment, globes were once “math- environment in just a few generations of unimaginable just ten years ago, is it impos- ematical instruments”. selection. He further suggests that speciation sible to believe that nature has used the same A typical standard globe of the seven- (or subspeciation) can occur in response to molecules to encode instructions about teenth and eighteenth centuries had a environmental stimuli, such as stress. This instructions we do not yet understand? diameter of 32.5 centimetres. The largest doesn’t seem so incredible in view of the way Darwin’s Radio, no matter how prepos- specimen in the National Maritime Mus- in which prophages become excised from terous or prophetic one thinks the science, is eum’s collection, which dates from 1688, has bacterial chromosomes in response to stress. superb ‘hard’ science fiction, speculating a diameter of 108 cm and thus an area equal Hard scientific evidence tells us that the about the connections among well-known to that of some 60 sheets of A4 paper. A con- scenario is possible. Although not every step facts. It is not a textbook of conventional siderable amount of information and error in evolution must be preceded by a rampant ideas. It is an entertaining, even riveting can be inscribed on such a sphere. Its maker, retroviral infection, the possibility that such a story, delivered poetically. It portrays scien- Vincenzo Coronelli, took advantage of sudden shake-up of the genome can be the tists as real people, responding to the intense both possibilities, filling his oceans and other fuel for evolutionary change may soon politics of the biomedical world, the funding blank spaces with accounts of discoveries, become dogma. Richard Goldschmidt’s idea imperative in public and private sector alike, depictions of peoples, ships and sea of the “hopeful monster” seemed strange in and the terrifying challenge of a disease that creatures, and definitions of celestial and his day, but monsters produced by homeotic threatens to decimate the human species. It terrestrial coordinates. At the other end of mutations are now on the cover of every text- takes a hard look at the challenges faced by a the globular scale were balls 7.5 centimetres book in genetics and developmental biology. woman scientist with radical ideas, and the in diameter, introduced in 1654 by Joseph Only the “hopeful” is missing at the moment. excitement of discovering a totally new way Moxon. These usually came in boxes the One of Bear’s wilder speculations is about of looking at biological evolution. Whether inside of which bore a depiction of the con- the rapidity and directedness of evolutionary you read it to pass a cold, snowy night by the stellations. Gentlemen carried them in their change. Mobile elements “hopping around fire, or to free your mind for the new para- pockets to orientate and amuse themselves like bugs on a hot griddle” can surely pro- digms that will emerge in the next millenni- during their travels. duce genetic change, but the likelihood of um, I promise you an engaging journey. I Most of the museum’s globes were print- beneficial genetic change would be nil. Bear Michael A. Goldman is in the Department of ed on paper gores (slips shaped to fit together concedes in his novel that there isn’t a simple, Biology, San Francisco State University, San into a sphere). In her catalogue, which occu- direct path to a new species — terrifying Francisco, California 94132-1722, USA. pies three-quarters of Globes at Greenwich, malformations, straight from an episode of Elly Decker gives the arrangement of the The X-Files, characterize the aborted fetuses gores (where relevant) and many other con- in the first three-quarters of the book. struction details of the globes and armillary But there is some basis for speculating spheres (representations of the principal that something other than a grossly random Around the world circles of spherical astronomy) owned by mess would result from a massive mobiliza- the museum. She also provides significant tion of transposable elements. First, pre- via Greenwich geographical and cartographical informa- ferred sites of integration can occur, and Globes at Greenwich: A Catalogue tion about each item and transcriptions of might ensure that a majority of elements of the Globes and Armillary their inscriptions as well as customary data land where they will do little harm. There is Spheres at the National Maritime about maker, dimensions, materials, date evidence that some repetitive-sequence ele- Museum and provenance. All this is done to the ments in the human genome harbour specif- edited by Elly Decker very highest standards. Silke Ackermann’s ic regulatory elements, like retinoic-acid Oxford University Press: 1999. 592 pp. response elements, which respond to devel- £95, $160 opmental signals. Thus, it is possible that J. L. Heilbron simple insertion of a retroviral element in the vicinity of a gene could result in an alteration Like many other things, globes are not what in the timing or positioning of its expression they used to be. The ordinary, modern in early development. The result could be a terrestrial variety has but one degree of different, yet perfectly viable, organism. freedom — a rotation around an axis As an established science fiction writer inclined to the vertical — as a hint that the who takes pride in keeping ahead of scientific Earth belongs to the Solar System. Early developments, Bear exploits the latest in modern Western globes, the dominant type nanotechnology in his grand scheme of evo- in the collection of Britain’s National Mari- lution. It’s hard for me to imagine Bear’s time Museum at Greenwich, customarily “mighty Wizard in our genes”, the consum- had two degrees of freedom, to allow a setting mate computer in our genomes, responding in latitude as well as longitude, and auxiliary to input from the environment, carrying out circles representing the horizon, the ecliptic crosstalk with other individuals and species, and the colures. Often these globes came in and playing back several different scenarios pairs, one celestial and one terrestrial, for the for ushering the human species to new levels easier learning not only of constellations and of achievement. But computer scientists say land masses, but also of spherical geometry that the next generation of data processors and elementary astronomy. If set for day will depend not on incremental improve- and place, a pair of globes can indicate the ments in the silicon microchips of today, stars visible above the horizon at night, but on a quantum leap into the realm of the directions of sunrise and sunset, the Gone global: a 1613 representation of the Earth. © 2000 Macmillan Magazines Ltd 16 NATURE | VOL 404 | 2 MARCH 2000 | www.nature.com