Jonathan Weiner is the author of “The Beak of the Finch,” which won the 1995 Pulitzer Prize for general nonfiction, and “Time, Love, Memory,” among other books. He teaches at Columbia Journalism School.

A DNA double helix. (REUTERS/National Human Genome Research Institute)

Here are two new books vying for our attention, “The Gene Machine” and “DNA Is Not Destiny.” One title is crying Yes, genes are everything! We are our genes! and the other No, we can go beyond them!

(Norton )

Yes and No have been tangled in this subject forever. After Charles Darwin published “On the Origin of Species” in 1859, he got a fan letter from his cousin Francis Galton. Galton asked Darwin if he’d agree that the number of geniuses in their family (here Galton was pleased to include himself) suggested the power of inheritance. Darwin wrote back modestly that he thought his own contributions, whatever they might be, came from hard work. (His personal motto was, “It’s dogged as does it.”) Ah, Galton replied, but surely the capacity for hard work runs in families, too.

In 1889, 30 years after “On the Origin of Species,” Galton published a book called “Natural Inheritance,” one of the primordial Yes books. There he declared that a gift for hard work or for “the Artistic faculty” is manifestly hereditary. Galton wrote, “A man must be very crotchety or very ignorant, who nowadays seriously doubts the inheritance either of this or of any other faculty.”

Galton dreamed of breeding better human beings through a program he called eugenics, from the Greek for “well born.” The program became so popular in this country that it led to a vogue for the baby name “Eugene.” But it also led to sterilization initiatives here, which, in turn, helped inspire the Holocaust.

Today we know a fantastic amount about the power of inheritance, but in some ways we’re still caught between Yes and No. Fourteen years ago, the National Institutes of Health and a consortium of other research groups around the world announced that they had finished reading the complete sequence of 3 billion letters that are written in the scroll of human DNA. The effort had cost a few billion dollars and a vast amount of time in collective person-hours: the equivalent of a single monkish scientist reading and copying the scroll for thousands of years. Now the job of reading DNA has been turbocharged. It can be done for about $1,000 and takes just a couple of days. Meanwhile, the parents of many of those babies know as little about inheritance as Galton did in 1859. Some of them have never heard of genes. How much should new parents be told about what is written there?

If you have a single typo in those 3 billion letters of your scroll of the human genetic code — if, say, at a certain point on Chromosome 2, you don’t have a G but an A — then every time you bruise your thigh, your body will repair your thigh muscle with bone. Eventually your entire body will be encased in bone, like a suit of armor or an ant’s exoskeleton. A single typo produces this condition, fibrodysplasia ossificans progressiva, which is extremely rare.

That’s how most of us think of our inheritance. We imagine that, for better or worse, each bit of genetic material decides our fates. And that’s more or less how Galton thought of it, too. But cases like these are highly unusual, as Steven J. Heine reminds us in “DNA Is Not Destiny.” Of all genetic diseases, only about 2 percent are caused by a single gene, like fibrodysplasia ossificans progressiva. Instead, most such diseases are caused by vast webs of genes — sometimes thousands and thousands of genes — working or blundering together with our experience, our environment. And of course we may carry the genes for most of these genetic diseases without the diseases showing up at all.

It’s the same story not only with diseases, but with almost any trait you can think of. Height, intelligence, creativity, willpower: They’re all shaped by vast webs of innumerable interactions between genes and environment, inheritance and experience, interactions that have hardly begun to be explored.

(Scientific American/FSG)

Heine is a psychologist at the University of British Columbia, and he’s interested in the reasons that people are so easily overimpressed by genetic test results. Whatever we know or don’t know about this subject, he says, “we are psychologically equipped to misunderstand it.” We like what one sociologist has called the OGOD framework — One Gene, One Disease.

A few years ago, Heine conducted an experiment with a group of Canadian university students. Most psychology studies are done with university students, making for a highly biased sample of the world’s population, which Heine and a few colleagues have termed WEIRD (Western, Educated, Industrialized, Rich and Democratic).

Heine had the students come to the lab and read a few newspaper articles. One group read an article about “obesity genes.” The message: Your genes control your weight. A second group read an article about eating and social pressures. The message there: How much your friends weigh affects your weight. A third group read an unrelated article about the agricultural production of corn. Later, each student was asked to sample a bowl of cookies. The ones who’d read about obesity genes ate the most cookies.

This helps explain why we have so much trouble getting DNA in any kind of stable perspective. We confuse it with fate, as Heine says. We imagine that whatever is written in our genes is all-powerful, unchangeable, somehow of the essence. And we want to think this way. We like to think this way. It serves certain purposes to think this way, as a headline from the Onion suggests: “Obesity caused entirely by genes, obese researchers find.”

The NIH is exploring the idea of sequencing the DNA of every newborn baby in the United States. There are many good arguments for and against. But unlike the reading of the DNA scroll, explicating the contents can’t easily be automated. Who is going to explain all of this to parent after parent as the science keeps racing ahead? Bonnie Rochman, a science journalist, explores the current scene in “The Gene Machine,” which, in spite of its title, is poised neatly between Yes and No.

We already do badly at the end of life. We don’t want to do badly at the beginning, too. At the end, all we want is a good death at home, and that’s not what most of us get. At the beginning, all we want is a healthy baby. We don’t want the iatrogenic gift of extra nervousness. As Rochman puts it (she sometimes has a mix-and-match approach to metaphors), “Will it heighten the anxieties of already hyper-anxious helicopter moms and dads, always waiting for the genetic shoe to drop?” Soon all those helicopter parents may be waiting for the helicopter stork.

And of course genetic testing is an issue not only at the beginning but at the other end, too. As I wrote this piece, two colleagues of mine at Columbia published a paper announcing that they have found an association between a gene called TMEM106B and a sudden decline of the brain at the age of 65. If you have two bad copies of this gene, you’re more likely to go into that accelerated decline.

Well, maybe that’s true and maybe not. This is only a first study. But I’m 63. It would be easy to find out if I have that gene. Do I want to know?


DNA Is Not Destiny
The Remarkable, Completely Misunderstood Relationship Between You and Your Genes

By Steven J. Heine

Norton. 344 pp. $26.95

The Gene Machine
How Genetic Technologies Are Changing the Way We Have Kids — and the Kids We Have

By Bonnie Rochman

Scientific American/Farrar Straus Giroux. 272 pp. $26