Evolution rising from the grave

Reactivation of a dormant message signals the dawn of a new humanity.

Darwin's Radio

Del Rey: 1999. 430 pp. $24

It is the dawn of the third millennium. It may be the dawn of a new humanity. It is the greatest scare since the bubonic plague. It manifests itself as cold-like symptoms in pregnant women, and as devastating malformations in their fetuses. It shakes the very sequence of the human genome. A cataclysm of biblical proportions in the making, it is dubbed Herod's influenza. A hitherto-silent human endogenous retrovirus has excised itself from the genome and become mobile and infectious once again.

SHEVA — scattered human endogenous retrovirus activation — has been seen in the past. In mass graves, where men and pregnant women had been slaughtered, their remains tested positive for SHEVA. It was also present in a well-preserved Neanderthal couple found in an ice cave — the woman's unborn child had met a violent end. The dread disease spreading across the face of the Earth today had broken out aeons before, at the dawn of Homo sapiens sapiens. Renegade scientists would show that SHEVA was not 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 possibilities and impossibilities of genetic engineering. 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 discoveries 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 challenged must be last week's dogma; tampering with today's can be hazardous to one's career. This the scientists in Darwin's Radio learn. The pioneering thinkers of yesterday are the devoted traditionalists of today. New ideas enter science grudgingly. New paradigms are resisted with a vengeance.

In writing Darwin's Radio, Bear treads on the toes of the scientific élite: “Ernst Mayr's kids are sweating ice cubes … Dawkins is beside himself.” He has mustered a cadre of facts, loosely connected and ill understood. There are little happenings at the periphery of Mendelian genetics, at the edge of neo-Darwinian theory, and what used to be beyond the realm of molecular biology. We know that bacteria contain extrachromosomal elements that transmit traits, such as drug resistance, between individuals and between species. We know that elements exist which insert in and excise from the genome, sometimes in response to environmental signals or stresses.

Such extraordinary magic isn't limited to single-celled organisms. Even before bacterial transposons, plasmids and phages were understood, Barbara McClintock had seen evidence for movable elements in maize, with all the prescience of Kaye Lang, Bear's heroine. We are faced with our growing knowledge of the human genome. It is littered with the footprints of ancient retrotransposons, ancient retroviral infections and shocking, widespread rearrangements. Stephen Jay Gould and others have advocated the notion that evolution occurs by punctuated equilibria. The fossil record shows bursts of speciation and extinction cutting across entire fauna and flora. Yet we seldom make the connection that vertical transmission of genetic information could occur within and among higher eukaryotic species, and that clusters of transposition events could occur in response to environmental signals. Bear the science fiction writer makes the connection for us.

Most of us believe that simple, incremental changes in allele frequencies, driven by the forces of genetic drift, mutation, recombination, migration and natural selection, are enough to explain evolution — from adaptation to speciation, to the origin of higher taxa. There is no compelling evidence to the contrary, but neither is there compelling evidence in favour of the idea; we simply haven't observed or catalogued the forces and changes that create new species. Bear fills this void in our understanding with the notion that radical changes in the genome, brought about by mobilization of transposable elements such as human endogenous retroviruses, result in rapid change at the subspecies or species level.

I'm not afraid of this concept. Bear goes a little further in suggesting that such change can occur over about a generation, an idea that might be a little too radical at the moment. However, he does mention data suggesting that fruitflies can adapt to a new environment in just a few generations of selection. He further suggests that speciation (or subspeciation) can occur in response to environmental stimuli, such as stress. This doesn't seem so incredible in view of the way in which prophages become excised from bacterial chromosomes in response to stress. Hard scientific evidence tells us that the scenario is possible. Although not every step in evolution must be preceded by a rampant retroviral infection, the possibility that such a sudden shake-up of the genome can be the fuel for evolutionary change may soon become dogma. Richard Goldschmidt's idea of the “hopeful monster” seemed strange in his day, but monsters produced by homeotic mutations are now on the cover of every textbook in genetics and developmental biology. Only the “hopeful” is missing at the moment.

One of Bear's wilder speculations is about the rapidity and directedness of evolutionary change. Mobile elements “hopping around like bugs on a hot griddle” can surely produce genetic change, but the likelihood of beneficial genetic change would be nil. Bear concedes in his novel that there isn't a simple, direct path to a new species — terrifying malformations, straight from an episode of The X-Files, characterize the aborted fetuses in the first three-quarters of the book.

But there is some basis for speculating that something other than a grossly random mess would result from a massive mobilization of transposable elements. First, preferred sites of integration can occur, and might ensure that a majority of elements land where they will do little harm. There is evidence that some repetitive-sequence elements in the human genome harbour specific regulatory elements, like retinoic-acid response elements, which respond to developmental signals. Thus, it is possible that simple insertion of a retroviral element in the vicinity of a gene could result in an alteration in the timing or positioning of its expression in early development. The result could be a different, yet perfectly viable, organism.

As an established science fiction writer who takes pride in keeping ahead of scientific developments, Bear exploits the latest in nanotechnology in his grand scheme of evolution. It's hard for me to imagine Bear's “mighty Wizard in our genes”, the consummate computer in our genomes, responding to input from the environment, carrying out crosstalk with other individuals and species, and playing back several different scenarios for ushering the human species to new levels of achievement. But computer scientists say that the next generation of data processors will depend not on incremental improvements in the silicon microchips of today, but on a quantum leap into the realm of molecules whose sequence of chemical bonds encodes information on a nanometric scale. If we can use the DNA molecule to carry out calculations in ways that were unimaginable just ten years ago, is it impossible to believe that nature has used the same molecules to encode instructions about instructions we do not yet understand?

Darwin's Radio, no matter how preposterous or prophetic one thinks the science, is superb ‘hard’ science fiction, speculating about the connections among well-known facts. It is not a textbook of conventional ideas. It is an entertaining, even riveting story, delivered poetically. It portrays scientists as real people, responding to the intense politics of the biomedical world, the funding imperative in public and private sector alike, and the terrifying challenge of a disease that threatens to decimate the human species. It takes a hard look at the challenges faced by a woman scientist with radical ideas, and the excitement of discovering a totally new way of looking at biological evolution. Whether you read it to pass a cold, snowy night by the fire, or to free your mind for the new paradigms that will emerge in the next millennium, I promise you an engaging journey.

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Goldman, M. Evolution rising from the grave. Nature 404, 15–16 (2000). https://doi.org/10.1038/35003625

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