Books: Nature Via Nurture

Several weeks ago, I read an article in the Wall Street Journal, about how children deprived of the opportunity to learn to speak when they are young are unable to acquire the skill later in life. I had long known that learning a second language is much easier prior to about age twelve, but I had never thought about the significance of that time period for learning one’s first language. Near the end of the article, there is a suggestion that the difficulty that autistic children have with language development may also be related to the “window” for such learning opening too early or too late.

Curious to read more by this author, I googled Matt Ridley and found that he not only writes regularly for the Wall Street Journal but that he has also written several books. Of these, Nature Via Nurture:Genes, Experience, and What Makes Us Human seemed particularly interesting, and I was pleased to find it available through the local library. It is written as popular science, not a textbook, so someone interested in learning in depth about how genes work would probably be disappointed. But for someone like me with an interest but little previous knowledge on the topic, it is a fascinating book.

My previous knowledge of genes was not much more than what I learned in tenth grade biology. I knew that genes are responsible for physical features such as hair and eye color, as well as a number of other traits that are not as easily defined or traced. I knew about dominant and recessive genes, which explain why I had red hair even though no one else in my immediate family did. I knew that genes are only part of the story, as even identical twins are not identical in every regard. And I knew that there was a great deal of research going on into the genetic basis for a number of physical and mental disorders.

I realized, however, early in the book, that I had no clear idea exactly what a gene was. (Much later in the book I found out that is in part because the word has been used in at least five different ways in the past century.) I asked my husband Jon, since his first career was in molecular biology, and he explained that a gene is the coding to produce a specific protein. That puzzled me even more – what does producing a protein have to do with having red hair or blue eyes? Jon did point out that genes are so small that scientists usually can only trace specific traits to part of a particular chromosome, not down to the level of a particular gene.

Ridley suggests that genes are more like a recipe in a cookbook than an architect’s blueprint. I don’t think I had ever thought of genes as being like a blueprint, but I suppose I did imagine there was some kind of match between one or more genes and the various physical and mental traits that make me who I am. At one point scientists probably thought that way also, and it was a surprise when they learned that humans only have about 30,000 genes, not the expected 100,000. The lower number did not seem sufficient to produce the complexity of the human being.

The answer, Ridley explains, is that genes are lines of instructions rather than patterns for the end product. Just as the common instructions “add,” “mix,” and “heat” are used to prepare a great many very different dishes in a typical cookbook, the instructions to create proteins produce a very wide variety of living things, depending on how those instructions are sequenced. Also, some genes function simply to turn other genes on or off at certain times. It’s hardly surprising, then, that we haven’t identified what genes are responsible for certain conditions despite a great deal of research into them. It’s surprising, really, that scientists have figured out as many as they have.

If genes were the blueprints that many imagined they were, it would make sense that one could categorize traits and conditions as being either a result of genetics, or a product of the environment. But as Ridley shows, because the timing of when genes turn on and off is so important (and he makes a point that, contrary to what I always assumed, genes continue to function throughout one’s life, not sure during the development period), the environment has a significant effect. Having a gene, and having the gene express itself in the typical fashion, are two very different things.

I read a few years ago that it is thought that left-handedness is a result of something that happens during fetal development. There is some genetic link, as having a left-handed parent does increase — slightly — one’s chances of being left-handed. But my husband and I, both of us left-handed, produced two undeniably right-handed boys. Presumably they carry whatever genes made Jon and me left-handed. But whatever environmental circumstances interacted with our genes to make us left-handed were apparently absent when Zach and Al were developing.

Ridley goes through a number of different examples of how genes and environment combine to produce various traits and conditions, both in lab animals and humans. One of the most interesting chapters is about schizophrenia, for which several different conditions have been identified as contributors to development of the disease. None of them by themselves will produce schizophrenia; only when they all combine does it occur. (And I don’t think that, as of the time the book was written, these various mechanisms had actually been definitely confirmed; they simply point to a likely way that the disease occurs.)

While one message of the book is that there are many things that we might have expected to be genetic which turn out to have a strong environmental component, another surprising discovery is how much genetics is responsible for things we might have assumed were a product of nurture. Personality, for instance, appears to be primarily a result of one’s genes, and is very little affected by the family one grows up in.

One of the questions I used to ask myself, growing up, was why I was such a perfectionist. I had read books about children who felt a strong need to achieve high grades or excel in sports because their parents pushed them. My parents never pushed me to get good grades; on the contrary, I remember my mother trying to persuade me (quite unsuccessfully) not to care so much about high grades. If my parents didn’t push me, why did I feel such a need to push myself?

My husband is also a perfectionist, and we both were aware of the sometimes negative effects we had experienced from our perfectionist tendencies. We tried hard not act on perfectionist impulses, especially when our young sons might model themselves on our behavior. I realize that some personal traits show through even when we’re trying not to let them, but it was still a surprise just how much of a perfectionist Zach was even as a preschooler.

As a toddler he refused to color with crayons because he couldn’t do it neatly enough to be happy with the results. When he started school and began to have written assignments, he would throw away a piece of paper as soon as he made a mistake. No amount of persuasion would get him to erase the mistake and continue with the marred piece of paper. Eventually he got better at dealing with his own lack of perfection, but by then I was convinced that heredity had a great deal to do with being a perfectionist. 

While one’s basic personality is rooted in heredity, however, the roles one plays in social groups are largely affected by family and peer groups, according to Ridley. I don’t think there was quite as much hard science supporting this section, but I mention it because I found it so interesting. Children seek to distinguish themselves from other children, and small differences in interest and ability eventually translate into significantly different patterns of behavior.

My sister and I, for instance, have both always tended to follow rules rather than disobey. Yet in our home, growing up, I was always the more compliant. How much of that was our personalities, and how much simply a matter of her being older and having come into conflict with our parents over things before I ever had reason to care about them? I saw the negative consequences of those conflicts, and decided they weren’t worth fighting over. Avoiding conflict became such a habit that to this day it is very difficult for me to push myself into one.

I will acknowledge that the book seems disjointed in places. All the chapters deal with the book’s major thesis, which is that not only can neither nature nor nurture be declared the “winner” in the classic nature vs nurture argument, but they can scarcely be separated to any meaningful degree. But there is not a clear progression from one chapter to the next. Later chapters build on earlier ones, but some add more to the overall picture more than others.

After reading the book, I read through some other readers’ reviews at amazon.com. (If I haven’t already read these in order to decide whether to read a book at all, I like to wait until after I finish the book to find out what others say so that their views don’t color my impressions as I read.) A number of readers say that some of Ridley’s other books are better. Some point to other books that are better on the same subject. As I haven’t read any of those other books, I can’t say if they’re right. But if you have an interest in the whole nature/nurture discussion, and don’t have a clearer understanding of genes than I did when I started, Ridley’s book is both enjoyable and informative.

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