Blueprint: How DNA Makes Us Who We Are

 

Robert Plomin, “Blueprint: How DNA Makes Us Who We Are,” MIT Press, 2018, 188 pp. plus 59 pages of notes

I was led to this book while listening to a Sam Harris podcast where he interviewed the book’s author.  I am a regular listener and $4 a month subscriber, to Harris’s podcasts. 

This book again pry’s open the lid on the Nature vs Nurture controversy.  A controversy I became aware in 1996 during the vehement attack on the authors who published the Bell Curve in 1994.  (I had to buy my own copy of Bell Curve as libraries tend not to carry it—I believe it is stolen and destroyed).  In any event, over the years the subject is now apparently not as dangerous to investigate, according to the author because the evidence now is overwhelming that nature is a major player in our psychological makeup.  The author has forty-five years’ experience as a psychologist at the center of genetic research on mental health and illness, personality and mental abilities and disabilities.  Most of the conclusions of this book have been available only in the last three years and the field dealing with DNA is rapidly developing.

My Notes:

Pg. viif:  What would you think if you heard about a new fortune-telling device that is touted to predict psychological traits like depression, schizophrenia, and school achievement?  What’s more, it can tell your fortune from the moment of your birth, it is completely reliable and unbiased.  The fortune teller is DNA and the ability to use it in this predictive manner has emerged only in the last three years, thanks to the rise of personal genomics. 

When psychology emerged as a science in the early twentieth century, it focused on the environmental causes of behavior.  This view that we are what we learn dominated psychology for decades.  However, beginning in the 1960s geneticists began to challenge this view.  Psychological traits from mental illness to mental abilities clearly run in families and there was a gradual recognition that family resemblance could be due to nature, or genetics, rather than nurture alone because children are 50 percent similar genetically to their parents.

Pg. viii:  The genetic contribution is not just statistically significant, it is massive.  Genetics is the most important factor shaping who we are.  It explains more of the psychological differences between us than everything else put together.  For example, the most important environmental factors, such as our families and schools, account for less than 5 percent of the differences between us in our mental health or how well we did at school—once we control for the impact of genetics.  Genetics accounts for 50 per cent of psychological differences, not just for mental health and school achievement, but for all psychological traits, from personality to mental abilities.  What makes us different environmentally are random experiences, not systematic forces like families. By studying genetically informative cases like twins and adoptees, behavioral geneticists discovered some of the biggest findings in psychology because, for the first time, nature and nurture could be disentangled.

Pg. ix:  The DNA differences inherited from our parents are the consistent, life-long source of psychological individuality, the blueprint that makes us who we are.

Pg. xiii:  The author has purposefully bypassed tangential topics that include evolution, epigenetics and gene editing.  (Note: I posted my notes on another book that does cover the evolutionary aspects of DNA.  The name of that book is also Blueprint and it was written in 2019 another worthwhile book:  Nicholas A. Christakis, “Blueprint: The Evolutionary Origins of a Good Society”, Little, Brown Spark, 2019, 419 pp.)

Pg. 6:

Fourteen characteristics significantly influenced by genetics (heritable)	Average genetic influence
Eye color	95%
Height	80%
Weight	70%
Breast Cancer	10%
Stomach ulcers	70%
Schizophrenia	50%
Autism	70%
Reading disability	60%
School achievement	60%
Verbal ability	60%
Remembering faces	60%
Spatial ability (e.g. navigation)	70%
General intelligence (e.g. reasoning)	50%
Personality	40%

 

Pg. 185:  The five biggest findings that this genetic research led to in psychology led to a new view of what makes us who we are.  Genetics accounts for most of the systematic differences between us—DNA is the blueprint that makes us who we are:

1.      Most measures of the environment used in psychology show substantial genetic influence.

2.      Heritability effects increases throughout the lifespan, especially for intelligence.  (It is true that the older you get the more you become your parents.)

3.      There is a substantial genetic link between normal and abnormal behavior;  behavior is on a bellcurve spectrum.

4.      Robust genetic links have been found between supposedly different traits, suggesting that genetic effects are general across traits rather than specific to each trait.

5.      Studying the environment while controlling for genetics revealed that environmental influences make children growing up in the same family as different as children reared in different families.

Pg. 34:  Findings in behavioral genetics replicate so strongly because the results are so big it is difficult to miss them if you look for them.  Inherited DNA differences account for 30 to 60 percent of the variance for most psychological traits.  Few other findings in psychology account for 5 percent of the variance. 

Pg. 35:  Karl Popper claimed that Freud’s theories were presented in a form that made them impossible to disprove, a sin against the first commandment of science which states that theories be not just testable but falsifiable.  Since Freud, thousands of studies in the behavioral sciences have investigated other aspects of parenting, such as warmth and discipline, as environmental influences on children’s development. 

Pg. 39:  The major systematic factor affecting divorce is genetics.  No environmental predictors of divorce have been identified in research after controlling for genetics.  Parental divorce is the best predictor of children’s divorce.  (This may be true now but in the past it was economic).

Pg. 52:  One of the big findings from behavioral genetic research is counterintuitive: genetic influences become more important as we grow older.  No psychological trait shows less genetic influence with age.  The domain where heritability increases most dramatically during development is cognitive ability. 

Pg. 53:  According to the majority view of intelligence researchers, the core of intelligence is ‘the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience’. 

Pg. 66:  Until now, psychologists have had to rely on behavioral symptoms to diagnose disorders.  For example, hallucinations, delusions and paranoia are signs of schizophrenia.  Severe swings in mood signal bipolar disorder.  Poor attention span and high activity levels suggest attention deficit hyperactivity disorder.  Lumping together these problems is not supported by genetic research. 

Pg. 71:  Two of the five big findings from behavioral genetics are about the environment.  The first is the nature of nurture.  The environment is not something ‘out there’ that happens to us passively.  Instead, we actively perceive, interpret, select, modify and even create environments, in part on the basis of our genetic propensities. (Once retired, we may have moved to Florida by our genetic tendencies--who knew?)

The second big finding about the environment involved why children who grow up in the same family are so different.  We now know that genetics makes siblings 50 percent similar, which means it also makes them 50 percent different.  Siblings are not completely different.  For example, if one sibling is diagnosed as schizophrenic, their siblings have a 9 percent risk, much greater than the rate of 1 percent across the general population…  Siblings correlate about 0.4 for intelligence. 

Pg. 90ff:  In summary, parents matter, schools matter and life experiences matter, but they don’t make a difference in shaping who we are.  DNA is the only thing that makes a substantial systematic difference, accounting for 50 percent of the variance in psychological traits.  The rest comes down to chance environmental experiences that do not have long-term effects.  However, genes are not destiny.  You can change.  But heritability means that some people are more vulnerable to these problems and also find it more difficult to overcome them.

Pg. 102:  If you take pairs of individuals randomly, their average IQ difference will be seventeen points.  First-degree relatives—parents and their offspring or siblings—differ by thirteen IQ points on average.

Pg. 109f:  In 1866 Gregor Mendel showed how heredity works functionally.  Mendel concluded through his experiments that there are two ‘elements’ of heredity for each trait in each individual and that offspring receive one of these two elements from each parent.  Until the 1950s it was still a mystery as to what these ‘element’ were.  Then Watson and Crick in 1953 described the famous double-helix structure of DNA which filled the bill for Mendel’s elements.  DNA is like a rope ladder with the two strands of rope held together by weak, easily broken run (adenine), C (cytosine, G (guanine) and T (thymine). 

 Pg. 115: The possibility of actually correcting a DNA mutation has been realized recently.  A gene-editing technique called CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats, pronounced ‘crisper’) can efficiently and precisely cut and replace a DNA mutation.  CRISPR has led to many advances in understanding how genes work.  Its most controversial feature is that it can be used to correct a DNA mutation in embryos, whose offspring would also be free of the mutation.

Pg. 119:  This book has a goal of providing the essential elements of DNA literacy, especially in relation to the DNA revolution in psychology.  This includes the structure and function of the double helix of DNA, the genetic code, and mutations in the genetic code, a particular type of mutation called a SNP, gene expression, genotyping SNPs, and SNP slips.  These are the ingredients of the DNA revolution.

Pg. 134: The heritability of psychological disorders and dimensions is caused by many DNA differences, not just one or two genes that pack a big punch, but tens of thousands. So huge GWA sample sizes of 10,000 or more are needed to detect these tiny associations.  And this is now possible and is being done.

Pg. 181:  Even though newborns cannot provide informed consent, they have nonetheless genetically been screened for decades—it is compulsory in most countries.  The original reason for screening newborns was phenylketonuria (PKU), a single-gene disorder that causes severe intellectual disability in about one in ten thousand babies and accounts for 1 percent of the intellectually impaired population in institutions.  Over 80 percent of those with untreated PKU require twenty-four-hour support and 70 percent cannot talk beyond single words.  So for forty years newborns around the world have had their heel pricked to get a drop of blood to test for PKU (it is called the Guthrie test).

Pg. 187:  The first wave of polygenic scores, consisting of tens of thousands of SNP associations from GWA studies, can predict 17 percent of the variance in height, 6 percent of the variance in weight, and 11 percent of the variance in school achievement, 7 percent of the variance in intelligence, and 7 percent of the variance in liability to schizophrenia.  Polygenic scores are already the best predictors we have for schizophrenia and school achievement.  Most importantly, unlike any other predictors, polygenic scores predict just as well from birth, and their prediction is causal, in the sense that nothing changes inherited DNA differences.