Blueprint: How DNA Makes Us Who We Are II

Approximately the first half of the book discusses Plomin's research with adopted children and twins, which he uses to identify the heritability of traits. The main finding is that what has typically been thought of as environmental influence is largely the expression of genes. For example, if a parent reads to a child and the child later becomes a proficient reader, rather than demonstrating a positive environmental effect, the actual situation is likely to be that the parent was a good reader and the child simply inherited the parent's reading ability. Overwhelmingly, children turn out more like their biological parents than their adoptive parents. This includes everything from adult weight to the amount of time spent watching TV: even when living in a different household from their parents, many of their characteristics mimic their parents' rather than the people in their adoptive households. Plomin's thesis, which I believe is correct, is that in the process of growing up, children should be encouraged to express their genes, because they are biologically attuned to specific stimuli and are not blank slates. The same studies also indicate that as people age they grow into greater concordance with their genetic heritage. Plomin finishes this section by saying that in a meritocracy, which is more or less what we live in (if you consider money important) some people are going to have a better genetic fit for high-paying jobs than others. He stresses that individuals should focus on meeting their genetic potentials, and, like Thomas Piketty, suggests that inequality should be balanced by taxation on wealth.

The remainder of the book switches to very recent studies which associate human traits with specific genes. After several false starts, rapid progress became possible with the advent of polygenic scoring, which links the presence of specific sets of alleles in single-nucleotide polymorphisms (SNPs) with probabilities for specific traits, psychological disorders and illnesses. For example, future years of educational attainment could theoretically be estimated at the moment of conception on the basis of the genetic sequencing of an embryo. Probabilities for adult height and weight can be estimated, along with probabilities for schizophrenia, bipolar disorder, autism and Alzheimer's disease. Polygenic scoring also indicates that different psychological disorders can be produced by the same alleles, meaning that the medical profession has been misunderstanding the underlying causes of disorders by focusing on symptoms rather than causes. This field is in its infancy, and it looks as if it will radically alter the fields of child development and disease prevention. The research already indicates that students at private, selective schools outperform students at public, unselective schools only because the students have higher academic potential to begin with: the quality of teaching is irrelevant to test score outcomes. Overall, Plomin is optimistic about the usefulness of this research, and I think he's right.

I do have a few quibbles, which I'll mention. Because he is working in the field of psychology, he uses many terms which I think are inadequately defined. For example, he accepts the g factor theory of intelligence, which I have always found spurious: it's another way of saying that smart people are just smart, and therefore they're good at everything. To be sure, there are some people who are good at a variety of intellectual tasks, but, in my experience, the range of actual skills in intelligent people is usually fairly narrow. Then, while saying that expensive private schools aren't worth the money, he overlooks the rather obvious sociological fact that having rich and successful friends – the kind of people you're likely to meet at expensive private schools – can and does improve people's fortunes.

My greatest complaint about the book is that Plomin has intentionally left out all references to evolution. This was probably a wise move to minimize hostile reactions to controversial material, but I think that seeing this through an evolutionary lens offers a wider picture. He has skirted the issue of what to do about poor minorities who inhabit dangerous neighborhoods. His position on the heritability of academic attainment seems to imply that poor minorities will never become wealthy by their own efforts, and that they should just be handed some money. This is a topic worthy of further discussion. If you take the long view of human existence, the traits that are the most beneficial change somewhat over time. Prior to civilization, the most important traits were probably social skills and the ability to hunt and gather food. When civilization arose, organizational and strategic skills such as those possessed by monarchs became the most valuable ones. During the Industrial Revolution, the Puritan work ethic and basic mechanical understanding sufficed. The kinds of skills that are valuable now, as noted by Plomin, are those associated with high educational attainment. I find this view a little myopic, because I think that we are in a transitional phase, and that the traits that seem essential at the moment may become less so in the future. The people who have been at the top end of the food chain recently, such as doctors and lawyers, are gradually losing their jobs to new technology, and this trend is likely to continue. Perhaps highly-paid software engineers will face a similar fate in the not-too-distant future. I have been thinking that the rise of the tech nerds may be brief: if further advances in technology obviate the need to hire them, their social deficiencies may become handicaps again. Since natural selection doesn't follow a path to a specific outcome, it is possible that social skills could make a comeback. Of course, this is all well beyond the scope of Plomin's book, but it's something to think about.

Plomin, it should be noted, is not a good writer – I found the repetition annoying – but the book is certainly worth reading, and you are definitely going to be hearing a lot about this topic in the years ahead.