The Metagene Gene
A review of Matt Ridley’s Genome: the Autobiography of a Species in 23 Chapters.
We are at a unique confluence of science and publishing where the results of the former are being dispersed by the latter at such a rate that even the most ardent reader of popular science books can hardly keep up. This is good news for science, of course, since its products are outstripping even Moore’s law of doubling every eighteen months, so updates and revisions are called for just as frequently. Lucky for publishers that readers are willing and able to plunk down a quarter of a hundred bucks to discover the secrets of the cosmos and life, and literary agents specializing in science tomes are demanding — and getting — five- and six-figure advances for their clients. And by most counts publishers are earning out those advances in a matter of months, thereby closing indefinitely the gap between C.P. Snow’s two cultures.
British science writer Matt Ridley is a participant in and beneficiary of this pleasant conjuncture, and he has rewarded his readers admirably with such bio-bestsellers as The Red Queen: Sex and the Evolution of Human Nature and The Origins of Virtue: Human Instincts and the Evolution of Cooperation, the latter, in my opinion, the most readable book to date on evolutionary ethics. In Genome Ridley continues with his expansion into larger themes, as he takes us on a roller coaster ride through the very foundation of life: DNA. The carnival-ride metaphor is apt because in Genome Ridley hits many highs and lows (depending on the complexity of the subject and his knowledge of it), and leaves the reader feeling a little dizzy at the end. The fault, on one level, is not Ridley’s, as he has taken on a subject vastly deeper and more complicated than can possibly be covered in a single volume — any one of the 23 chapters could have been a book in itself. But for readers with little to no knowledge of the subject Ridley provides a highly readable and informative encapsulation of the science that promises to do for the 21st century what nuclear physics did for the 20th. Revolution is in the air and Ridley has his finger on its pulse.
Ridley’s technique is at once clever and delimiting: Each chapter represents a chromosome, for which he has chosen a single entity supposedly determined or influenced by that chromosome. To wit: Chromosome 6: Intelligence; Chromosome 7: Instinct; Chromosome 8: Self-Interest. It is a facile literary device to help readers get their minds around this illimitable subject, but I fear that it gives the wrong impression, disclaimers notwithstanding, that such things as intelligence, instinct, or self-interest are wholly located on that chromosome (and, therefore, genetically programmed and biologically determined). I have the same concerns about books with such titles as The Math Gene or Mean Genes that, again, disclaimers notwithstanding, propagate the myth these same authors claim to be debunking that mathematics or meanness (or whatever) is wholly or even predominantly determined by our genes.
Only half in jest I sometimes wonder if there isn’t a metagene gene — a gene that causes people to think that everything is in our genes. Evolutionary psychologists could have a field day with the metagene gene concept: people tend to view behavior as genetically caused because back in the paleolithic those individuals who were more inclined to view behavior as genetically determined won more copulations and thus passed on their metagene genes through more offspring. Of course, paleolithic cave persons knew nothing about genes, so we must postulate that they tended to view the actions of others as either largely capricious or largely determined. The latter would be high in metagene genes, and they, of course, would be better adapted and more successful because living in a deterministic world better allows one to determine cause and effect relationships, and that is what leads to enhanced survival and the propagation of one’s genes, including one’s metagenes.
Okay, I’m being rather facetious (and wondering if this too is in my genes), and I do think evolutionary psychology has much value to add to the social sciences (indeed, I did some of it myself in my book How We Believe, in an attempt to explain the evolutionary origins of religion). But the glut of metagene books, I fear, is doing more harm than good in the public understanding of how science and nature really work. Fortunately, in most cases Ridley does an admirable job of clarifying the enormous complexities involved in gene-environment interactions, demonstrating in numerous cases that it is next to impossible to say that any complex human trait (such as intelligence or athletic ability) is, say, 60% genetic and 40% environment.
In Chromosome 11: Personality, for example, Ridley describes a gene called D4DR located on the short arm of the 11th chromosome. D4DR codes for dopamine, a neurotransmitter released by neurons that, when received by other neurons receptive to its chemical make-up, sets up dopamine pathways throughout the brain that stimulates the organism to be active (or not, if a shortage exists). A complete lack of dopamine, for example, causes patients (or rats), to slip into a virtual catatonic state. High levels of dopamine turn humans schizophrenic and rats frenetic. Dopamine stimulation, in fact, is the basis of the famous experiment where rats pressed a bar to stimulate their so-called “pleasure center,” which they did until collapsing in exhaustion. Humans have been known to do the same thing, but they don’t need scientists to hook them up.
Here Ridley is summarizing the fascinating work of Dean Hamer who, in his quest to find genes for smoking and homosexuality, discovered the gene (or, more precisely, the gene-complex) for thrill-seeking personality. It turns out that the D4DR gene sequence is repeated on chromosome 11. Most of us have four to seven copies, but some people have two or three, while others have eight, nine, ten, or eleven copies. More copies of D4DR means lower levels of dopamine, which translates into higher novelty seeking behavior to artificially produce more dopamine (jumping off buildings and out of planes will do that for you). Hamer took 124 people who scored high on a survey measuring their desire to seek novelty and thrills (bungee-jumpers and sky-divers knock the roof off these tests), then looked at their DNA — specifically, chromosome 11. He found that people who like to jump off buildings and out of planes had fewer copies of D4DR than those who prefer knitting and watching grass grow. (Presumably those who like to watch sky-divers go splat are higher in the mean gene category.)
When Hamer’s research was picked up in the media headlines declared that scientists had discovered the novelty-seeking gene, implying that perhaps all of our personality traits are so genetically coded. Alas, if only it were that simple — whenever you get that urge to jump off the top of Yosemite’s half dome, just take a dopamine tablet and you’ll prefer to stay on the marked trails. Fortunately for his readers, Ridley is honest enough to report the other side to this story. When you actually read the original research it turns out that Hamer is claiming to explain no more than four percent of novelty seeking behavior by D4DR sequences. That is, if we say that humans vary by 100 percent in their novelty seeking behavior — catatonics on one end and X-Game skateboarders careening down hills at 50 mph two inches off the ground on the other — only four percent of that variance can be accounted for by D4DR. That’s it! That’s nothing, as Ridley concludes:
This is the reality of genes for behaviour. Do you see now how unthreatening it is to talk of genetic influences over behaviour? How ridiculous to get carried away by one “personality gene” among 500? How absurd to think that, even in a future brave new world, somebody might abort a foetus because one of its personality genes is not up to scratch — and take the risk that on the next conception she would produce a foetus in which two or three other genes were a kind she does not desire? Do you see now how futile it would be to practise eugenic selection for certain genetic personalties, even if somebody had the power to do so? You would have to check each of 500 genes one by one, deciding in each case to reject those with the “wrong” gene. At the end you would be left with nobody, not even if you started with a million candidates. We are all of us mutants. The best defence against designer babies is to find more genes and swamp people in too much knowledge.
Well said. But is this the general conclusion about genes that readers will come away with in this book? I hope so, but fear not.
One quibble I had with Genome comes about in the final chapter, Chromosome 22: Free Will. Granted one cannot cover in one book the fine nuances of all positions in every debate in this vast field, but in one area that I do know something about — personality development — Ridley leans far too heavily on the work of psychologist Judith Rich Harris, whose book, The Nurture Assumption, generated much heat (and, thankfully, some light) for its attack on psychology’s long love affair with nurture arguments. Ridley writes: “Rich Harris has systematically demolished the dogma that has lain, unchallenged, beneath twentieth-century social science: the assumption that parents shape the personality and culture of their children.” It turns out, Harris argues, that parents don’t count for much at all in the development of adult personality. What does count? Genetics, of course, and peer groups. Families just don’t matter.
Baloney. The research by U.C. Berkeley behavioral scientist Frank Sulloway, summarized in his book Born to Rebel, shows that both historically and presently, siblings and family dynamics are highly influential in the development of personality, which, in turn, shapes the interactions with siblings and parents, that feeds back into personality, and so forth, round and round, in a chaotic and complex feedback loop. Now, whether you prefer Harris’ peer-group theory or Sulloway’s family-dynamics theory (or like an amalgamation of the two, with some Bowlby attachment theory and Jerome Kagan developmental theory thrown in for good measure), it would be helpful to readers to at least get a paragraph or two about competing models. Harris is not without her critics (and neither is Sulloway, or Bowlby or Kagan for that matter), and for readers to understand the nuances of the complex development of something called “personality,” they really need to be given a few alternative views. Given that I have not mastered the literature for all 23 of Ridley’s chapter subjects, this example leaves me wondering what else he might have left out.
That critique aside, however, Ridley’s numerous caveats throughout the book warning readers not to take the metagene gene argument too seriously, Genome is an important contribution to the popular science literature in helping us find that delicate balance between nature and nurture, even if the tendency to so delineate such an argument may itself genetically influenced!
(HarperCollins, 2001, ISBN 0060894083)
This review was originally published in American Scientist.