Following his highly praised and bestselling book Genome: The Autobiography of a Species in 23 Chapters, Matt Ridley has written a brilliant and profound book about the roots of human behavior. Nature via Nurture explores the complex and endlessly intriguing question of what makes us who we are.
In February 2001 it was announced that the human genome contains not 100,000 genes, as originally postulated, but only 30,000. This startling revision led some scientists to conclude that there are simply not enough human genes to account for all the different ways people behave: we must be made by nurture, not nature. Yet again biology was to be stretched on the Procrustean bed of the nature-nurture debate. Matt Ridley argues that the emerging truth is far more interesting than this myth. Nurture depends on genes, too, and genes need nurture. Genes not only predetermine the broad structure of the brain, they also absorb formative experiences, react to social cues, and even run memory. They are consequences as well as causes of the will.
Published fifty years after the discovery of the double helix of DNA, Nature via Nurture chronicles a revolution in our understanding of genes. Ridley recounts the hundred years' war between the partisans of nature and nurture to explain how this paradoxical creature, the human being, can be simultaneously free-willed and motivated by instinct and culture. Nature via Nurture is an enthralling,up-to-the-minute account of how genes build brains to absorb experience.
説明の主軸はNature派の主張もNurture派の主張も正しく，人間の本性は遺伝子にも影響を受け，環境にも影響を受ける，もっと正確にいうと環境を通じて遺伝子が発現する（Nature via Nurture）．それはミクロの仕組みを丁寧にみれば理解が深まるというもの．
Ridley writes that the switches controlling our 30,000 or so genes not only form the structures of our brains but do so in such a way as to cue off the outside environment in a tidy feedback loop of body and behavior. In fact, it seems clear that we have genetic "thermostats" that are turned up and down by environmental factors. He challenges both scientific and folk concepts, from assumptions of what's malleable in a person to sociobiological theories based solely on the "selfish gene."
Ridley's proof is in the pudding for such touchy subjects as monogamy, aggression, and parenting, which we now understand have some genetic controls. Nevertheless, "the more we understand both our genes and our instincts, the less inevitable they seem." A consummate popularizer of science, Ridley once again provides a perfect mix of history, genetics, and sociology for readers hungry to understand the implications of the human genome sequence.
So...great book, just don't shell out any money if you already read "Nature Via Nurture".
The discussions in this book are dramatically and importantly different from other discussions of "Nature/Nurture", and I can hardly recommend it strongly enough. What is different is the degree of specificity that Ridley brings to the conversation. He demonstrates from a dozen different points of view HOW causality flows both ways, from the genes to the environment and back. He also pokes holes in logical fallacies one hears all the time - for example, the assertion that a feature is not genetic because the specific genes have not (and in some cases may not ever) been identified. A well-constructed twin study positively identifies heritability of traits; tracking that heritability back to a spot on a chromosome is useful and interesting but not necessary.
There is also basic science here that the lay reader might not otherwise learn for years. For instance, until very recently it was thought that there was a one to one correlation between genes and their proteins. It was also unknown what, if any, purpose breaking genes apart into exons on the chromosome served. Now we have discovered that many - ninety five on one mouse gene - different versions of one exon can exist on the chromosome, allowing one gene to make many different versions of its protein. Different versions mediated by... environment, of course.
Much of the information here is counter-intuitive. For instance, the more egalitarian a society is, the more the heritabilaty of traits becomes manifest. Potentially confusing, certainly mind-bending, and who better than Ridley to explain it?
If you are interested in biology, read this book.
As Ridley points out, the ideological question of whether human behavior is more the product of heredity or environment has distinguished not just scientists, but fascists and communists, just as surely as any of their political theories. During the well-known sociobiology debates, technical issues were rarely discussed much less resolved. Rather politics and the question of hidden agendas always raised its head.
While virtually all scientists and indeed anyone with a modicum of learning, observational skills, and common sense, have long known that heredity and environment were interacting factors in human nature, that answer truly satsifies almost no one. We still argue over the many implications of being either victims of our genes, victims of our environment, or somehow free of both. We still seek the answer to the technical question of *how* exactly biology and environment interact to produce living things, especially ourselves. And more abstractly, we still want to know what defines us as individuals, and what determines our fate. A lot seems to hinge on the answer, which is why asking the "question of nature and nurture" never fails to bring out strong opinions.
In the most common caricature, the hereditarians insist that we have a are products of our biological history and have a specific fixed nature rather than being blank slates formed by our environment. The environmentalists insist that what nature wires up is a flexible general purpose organism capable of above all learning and being shaped by their environment. In early political theory, the difference had serious implications because for example things like "social contract theory" revolved around what human beings were supposed to be like in a "state of nature" without society. Were we gentle, peaceful, noble savages; or brutish, win-at-all-costs warmongers competing over territory and mates?
In _Nature_Via_Nurture_, Ridley freely exhibits both his consummate writing skills and his ability to make important scientific points clear without oversimplifying them. His message is crystal clear. Genes are everything. Nothing about us, including our nurture, can be fully understood without appreciating the role that genes play both in constructing us and in providing ongoing biological functions.
But wait ... there's a catch. A big one. The hereditarians are right. Our biological legacy is all important. Yet the hereditarians typically understand or at least emphasize only part of the importance of genes. The environmentalists made the serious mistake of fearing the role of genes because they, along with the hereditarians, assumed that genes were little dictators that caused things to happen. "Genetic determinism" is supposedly something no one is silly enough to believe in, yet when the discussion gets heated, it seems to be the default position that nearly everyone takes. In arguing anachronistically about "free will" vs. "determinism," we instinctively place genes into the role of neccessity, regardless of which side we are on. But it turns out that genes didn't cooperate with that characterization as we studied their role more closely.
This was also part of the underlying framework of biological science. It was considered a classic mistake, so-called "Lamarckism," to have fallen for the claim that behavior and experience could possibly influence our genes. The influence was one-way, an assumption that was commonly assumed to apply in evolution, in development, and in behavior.
But there was an "underground" among biological theorists, long scattered and individually easily dismissed critiques which eventually have coalesced into a single powerful new interactionist framework. Genes are indeed everything, but their influence goes both ways. And this happens at all levels. Not only are the chemical effects of genes influenced by the environment, but development is chanelled in various ways by experience, and the evidence is growing that behavior even has an influence on what happens in evolution. Organisms actively modify, select, and construct their own niches, according to the preferences set largely by their genes, and this is an important factor in reproductive fitness, the selection criteria of biological fate.
And so the environmentalists are right also. Experience and behavior do matter in shaping us. Not just through learning and development but even through evolution. And they matter not in spite of our genes, but because of them. Still, this clearly doesn't make us blank slates. Genes respond but they are not infinitely flexible responders. The do set limits in some sense and they do establish reliable trajectories. Yet they are not blueprints for our final form, nor do they compel our behavior. Genes help build dynamic mechanisms capable of responding to the environment in particular ways to make it possible for living things to carve out their own way of life. Here the hereditarians are right as well, having more "instincts" can make us more flexible rather than less flexible. We needn't be a blank slate to be capable of flexible behavior or "free will," we need the capacity to choose and some basis for making and acting on choices.
Just as he did for social behavior in _Origins of Virtue_, Matt Ridley sets a sane, clear, modern scientific tone for the next round of the neverending "nature and nurture" debate, and provides a bridge from the anachronistic abstract question of free will and determinism to the modern science that has the potential to address real answers to real questions.