Summary

An extension of Genome. In 1 sentence: Genes are designed to take their cues from nurture.

Key Takeaways

• Genes are designed to take their cues from nurture.
• The source of the difference between a chimpanzee and a human being lies not in the dif­ferent genes but in the same set of 30,000 genes used in a different order and pattern.
• Men like pretty, young, faithful women, while women like rich, ambitious, older men.
• There might be all sorts of cultural aspects to a behavior that is grounded in instinct.
• “Men pay most atten­tion to what is their own: they care less for what is common.” – Aristotle
• Disagreement thrives on uncertainty.
• Paradoxically, the more equal we make society, the higher heritability will be, and the more genes will matter.
• People differ in personality more if they have different genes than if they are reared in different families.
• A family is a bit like vitamin C: you need it or you will become ill, but once you have it, consuming extra does not make you healthier.
• Raising the safety net of the poorest does more to equalize opportunity than reducing inequality in the middle classes.
  • In the jargon of the scien­tist, the effect of the environment is nonlinear: at the extremes, it has drastic effects. But in the moderate middle, a small change in the environment has a negligible effect.
• Living in an intellectual home does make you more likely to become an intellectual but the older you grow, the less your family background predicts your IQ and the better your genes predict it.
• Critical-period imprinting is everywhere. There are a thousand ways in which human beings are malleable in their youth, but fixed once adult.
• Active learning occurs when there is some discrepancy between an expected coincidence and what actually happens.
  • Surprise, pleasant or unpleasant, is more informative than predictability.
• Genes are the mechanisms of experIence.
• Parents may reinforce nature with nurture, but they do not create the difference. Peers on the other hand (can) make a big difference.
• Small differences in innate character are exagger­ated by practice, not ironed out.
• How to make people ignore race: give them another, stronger clue to coalition membership. (Think of sports teams and fandom.)

What I got out of it

Ridley’s Nature Via Nurture is an extension of his work in Genome and drives home the point that “genes are designed to take their cues from nurture.”

I enjoyed the wider variety of examples in which this point was illustrated but didn’t have any eye-openers as I did when I read Genome. 

Worthwhile for those who have read Genome and want to continue Ridley’s exploration on the topic, otherwise stick with Genome.

Summary Notes

Prologue – Twelve Hairy Men

Nature versus nurture has been declared everything from dead and finished to futile and wrong – a false dichotomy. Everybody with an ounce of common sense knows that human beings are a prod­uct of a transaction between the two.

Genes are designed to take their cues from nurture.

My argument in a nutshell is this: the more we lift the lid on the genome, the more vulnerable to experience genes appear to be.

Human nature is indeed a combination of:

• Darwin’s universals
• Galton’s heredity
• James’s instincts
• De Vries’s genes
• Pavlov’s reflexes
• Watson’s associations
• Kraepelin’s history
• Freud’s formative experience
• Boas’s culture
• Durkheim’s division of labor
• Piaget’s development
• and Lorenz‘s imprinting. 
• You can find all these things going on in the human mind. No account of human nature would be complete without them all.

The Paragon of Animals 

The fact that two animals are different does not mean they cannot also be similar.

The difference in mind between man and the higher animals is certainly one of degree and not of kind. We have seen that the senses and intuitions, the various emotions and faculties, such as love, memory, attention, curiosity, imitation, reason, of which man boasts, may be found in an incipient, or even sometimes in a well-developed condition, in the lower animals.

Infanticide brings genetic rewards to males, who thereby become more fecund ancestors than males that do not kill babies; hence most modern gorillas are descended from killers. Infanticide is a natural instinct in male gorillas. But in chimps females have “invented” a counterstrategy that largely averts infanticide: they share their sexual favors widely.

The source of the difference between a chimpanzee and a human being lies not in the dif­ferent genes but in the same set of 30,000 genes used in a different order and pattern.

To make grand changes in the body plan of animals, there is no need to invent new genes, just as there is no need to invent new words to write an original novel. All you need to do is switch the same ones on and off in different patterns. Merely by adjusting the sequence of a promoter, or adding a new one, you could alter the expression of a gene. And if that gene is itself the code for a transcription factor, then its expression will alter the expression of other genes. Just a tiny change in one promoter will produce a cascade of differences for the organism. 

A Plethora of Instincts 

The expression of a fixed, innate instinct must often be triggered by an external stimulus.

In every culture, bar none, women rated financial prospects more highly than men. The difference was highest in Japan and lowest in Holland but it was always there. This was not the only difference he found:

• In all 37 cultures, women wanted men older than themselves. 
• In nearly all cultures, social status, ambition, and industriousness in a mate mattered more to women than to men. 
• Men by contrast placed more emphasis on youth and physical appearance. 
• In most cultures men also placed slightly more emphasis on chastity and fidelity in their partners, while being much more likely to seek extramarital sex themselves. 
• Men like pretty, young, faithful women, while women like rich, ambitious, older men.

By proving how universal so many sex differences in mating preferences are, Buss has thrown the burden of proof onto those who would see a cultural habit rather than an instinct. But the two explanations are not mutually exclusive. They are probably both true. Men seek wealth to attract women; therefore women seek wealth because men have it; therefore men seek wealth to attract women; and so on. If men have an instinct to seek the baubles that lead to success with women, then they are likely to learn that within their culture money is one such bauble. Nurture is reinforcing nature, not opposing it.

With the human species, as Dan Dennett observed, you can never be sure that what you see is instinct, because you might be looking at the result of a reasoned argument, a copied ritual, or a learned lesson. But the same applies in reverse.

There might be all sorts of cultural aspects to a behavior that is grounded in instinct. Culture will often reflect human nature rather than affect it.

• To be good at empathizing you need a domain, or module, in your mind that learns to treat animate creatures intuitively as having mental states as well as physical properties. 
• To be good at systemizing, you need a domain that learns how to intuit cause and effect, regularities and rules. 
• These are separate mental modules, separate skills, and separate learning tasks.

To build a brain with instinctive abilities, the Genome Organizing Device lays down separate circuits with suitable internal patterns that allow them to carry out suitable computations, then links them with appropriate inputs from the senses. In the case of a digger wasp or a cuckoo, such modules may have to “get the behavior right” the first time and may be comparatively indifferent to experience. But in the case of the human mind, almost all such instinctive modules are designed to be modified by experience. Some adapt continuously throughout life; some change rapidly with experience, then set like cement. A few just develop according to their own timetable.

Plato‘s Republic has been called a “managerial meritocracy” in which the same education is available to all, so the top jobs go to those with the innate talent for them. Everything is governed by strict rules:

• The “rulers,” who make policy, are assisted by the “auxiliaries,” who provide a sort of civil and defense service. 
• Together these two classes are called the “guardians,” and they are chosen on merit, which means on native talent. 
• But to prevent corruption, the guardians live lives of austere asceticism, unable to own property, to marry, or even to drink from gold cups. They live in a dormitory, but their miserable existence gladdens their hearts because they know it is for the good of the society as a whole.

Karl Popper was not the first, nor will he be the last, philosopher to call Plato’s dream a totalitarian nightmare. Even Aristotle pointed out that there was not much point in a meritocracy if merit did not bring rewards – of wealth and sex as well as power: “Men pay most atten­tion to what is their own: they care less for what is common.”

A Convenient Jingle 

Disagreement thrives on uncertainty.

To the extent that they can be teased apart, nature prevails over one kind of (shared) nurture when it comes to defining differences in personality, intelligence, and health between people within the same society. Note the caveats.
Paradoxically, therefore, the more equal we make society, the higher heritability will be, and the more genes will matter.

Even in such a prototypically “cultural” thing as religion, the impact of genes cannot be ignored and can be measured. There is a partly heritable aspect of human nature, which might be called religiosity, and it is distinct from other attributes of personality. 

This can be detected using simple questionnaires, and it predicts fairly well who will end up becoming a fundamentalist believer within any particular society.

Champions of nurture repeatedly state that “the gene for x” means a gene that always and only causes behavior x; the champions of nature reply that they merely mean the gene increases the probability of behavior x, compared with other versions of the same gene.

For nearly all measures of personality, heritability is high in western society: identical twins raised apart are much more similar than fraternal twins raised apart. 

When everybody has similar access to food, the ones who put on weight fastest will be the ones with certain genes. So variation in weight can be inherited, even while changes in the aver­age can be environmental.

It is also the first gene to be associated so strongly with depression. It proves just how easy is the leap from a spelling change in a DNA code to a real difference in personality. A change in a protein recipe can indeed result in a change in personality.

People differ in personality more if they have different genes than if they are reared in different families.

A family is a bit like vitamin C: you need it or you will become ill, but once you have it, consuming extra does not make you healthier.

A few features of human behavior prove to be less heritable:

• The sense of humor
• Food preferences seem to be barely heritable – you get your food prefer ences from your early experience, not your genes. 
• Social and political attitudes show a strong influence from the shared environment – liberal or conservative parents seem to be able to pass on their preferences to their children. 
• Religious affiliation, too, is passed on culturally, rather than genetically, though not religious fervor.
• Unlike personality, intelligence does seem to receive a strong influence from the family.

The one physical feature that does clearly predict intelligence is brain size. Brains are composed of white matter and gray matter. Gray matter volume must be “due completely to genetic factors and not to environ­mental factors.”

Gray matter consists of the bodies of neurons, and the new correlation implies that clever people may literally have more neurons, or more connections between neurons, than normal people do.

IQ is approximately 50 percent “additively genetic”; 25 percent is influenced by the shared environment; and 25 percent influenced by environmental factors unique to the individual. Living in an intellectual home does make you more likely to become an intellectual.

However, these average figures conceal two very much more interesting features:

• You can find samples of people in which variation in IQ is much more environmental and much less genetic than the average. The heritability of IQ depends strongly on socioeconomic status.
  • This is a finding with obvious significance for policy. It implies that raising the safety net of the poorest does more to equalize opportunity than reducing inequality in the middle classes.
  • In the jargon of the scien­tist, the effect of the environment is nonlinear: at the extremes, it has drastic effects. But in the moderate middle, a small change in the environment has a negligible effect.
• The second surprise hidden in the average figures is that the influence of genes increases and the influence of shared environment gradually disappears with age. The older you grow, the less your family background predicts your IQ and the better your genes predict it.

The environment acts as a multiplier of small genetic differences, pushing athletic children toward the sports that reward them and pushing bright children toward the books that reward them.

Nature plays a role in determining personality, intelligence, and health – that genes matter. But it does not tell you that this role is at the expense of nurture.

Behavior genetics does not discover what determines behavior; it discovers what varies.

The Madness of Causes 

The extraordinary spread of psychoanalysis between 1920 and 1970 owed more to marketing than to therapeutic triumphs. By talking to patients about their childhood, analysts offered humanity and sympathy that had not been available before. This made them popular when the alternatives were a deep barbiturate sleep, insulin coma, lobotomy, and electroshock convulsions: all unpleasant, addictive, or dangerous.

First, they show that the heritability of schizophrenia in western society is high: roughly 80 percent, or about the same heritability as body weight and consider­ably more than personality. But second, they reveal that many genes are involved. 

A well-known fact about schizophrenia: more schizophrenics are born in winter than in summer.

“Rational thought imposes a limit on a person’s concept of his relation to the cosmos.”

A century after the syndrome was first identified, the only two things that can be said for certain about schizophrenia are that blaming unemotional mothers was wrong, and that there is something highly heritable about the syndrome. Many genes clearly influence susceptibility to schizophrenia, many may respond to it in compensation, but few seem to cause it.

Genes in the Fourth Dimension 

A student of animal behavior should ask four questions about a particular behavior: 

• What are the mechanisms that cause the behavior? 
• How does the behavior come to develop in the individual (Lehrman’s question)? 
• How has the behavior evolved? 
• What is the function or survival value of the behavior (Lorenz’s question)?

Formative Years 

Imprinting: the concept of the critical period – the window during which environment acts irreversibly upon the development of behavior.

In most men the ring finger is longer than the index finger. In women the two fingers are usually the same length. John Manning realized that this was an indication of the level of prenatal testosterone to which people had been exposed while in the womb: the more testosterone, the longer the ring finger.

The length of the ring finger and indeed the fingerprint on it are imprinted in the womb. They are products of nurture – for surely the womb is the very embodiment of the word “nurture.” The comforting belief that nurture is more malleable than nature relies partly on the mistaken notion that nurture is what happens after birth and nature is what happens before birth.

Reasoning that “ought” can be derived from “is” is called “naturalistic fallacy.” To base any moral position on a natural fact, whether that fact is derived from nature or from nurture, is asking for trouble. In my morality, some things are bad but natural, like dishonesty and violence; others are good but less natural, like generosity and fidelity.

The brain is open to calibration by experience in the early weeks of life, after which it sets. Only by experiencing the world through its eyes can an animal sort the input into separate stripes. Experience seems actually to switch on certain genes, which in turn switch on others.

Critical-period imprinting is everywhere. There are a thousand ways in which human beings are malleable in their youth, but fixed once adult.

Lorenz’s notion of imprinting was a great insight that has stood the test of time. It is a marriage of what I call nature via nurture. The invention of imprinting as a way of ensuring the flexible calibration of instinct was a masterstroke of natural selection. Without it, either we would all be born with a fixed and inflexible language unchanged since the Stone Age, or we would struggle to relearn each grammatical construction.

Learning Lessons 

Modern learning theorists have modified Pavlov’s idea in one crucial way. They argue that the active learning occurs not when the stimulus and reward continue to appear together, but when there is some discrepancy between an expected coincidence and what actually happens. If the mind makes a “prediction error” – expecting a reward after a stimulus and not getting it, or vice versa – then the mind must change its expectation: it must learn.

Surprise, pleasant or unpleasant, is more informative than predictability.

The acquisition of a memory is distinct from its retrieval; different genes are needed in different parts of the brain.

People, and animals, are so equipped that they find some things easier to learn than others.

“Prepared learning:” this was almost the exact opposite of imprinting. 

• In imprinting, a gosling becomes fixated on the first moving thing it encounters – mother goose or professor. The learning is automatic and irreversible, but it can attach to a wide variety of targets. 
• In prepared learning, the animal can learn to fear a snake very easily, for instance, but finds it hard to learn to fear a flower: the learning attaches only to a narrow range of targets, and without those targets it will not happen.

There is a degree of instinct in learning, just as imprinting shows that there is a degree of learning in instinct.

Clearly Pavlovian conditioning can create a fear of any kind. But it can undoubtedly establish a stronger, quicker, and longer-lasting fear for snakes than for cars, and so can social learn­ing.
That a fear may be easily learned does not mean it cannot be pre­vented or reversed.

Conundrums of Culture  

The reason the human species dominates the planet and gorillas are in danger of extinction lies not in our 5 percent of special DNA or in our ability to learn associations, or even in our ability to act culturally, but in our ability to accumulate culture and transmit information, across the seas and across the generations.

According to the scanty fossil evidence, speech, unlike manual dexterity, appeared late in human evolution.

But language is not the same thing as speech: syntax, grammar, recursion, and inflection may be ancient, but they may have been done with hands, not voice. 

If the human brain expanded to cope with social complexity in large groups – with cooperation, betrayal, deceit, and empathy – then it could have done so without inventing language or developing culture. Yet culture does explain the ecological success of human beings. Without the ability to accumulate and hybridize ideas, people would never have invented farming, cities, medicine, or any of the things that enabled them to take over the world. The coming together of language and technology dramatically altered the fate of the species. Once they came together cultural take-off was inevitable. We owe our abundance to our collective, not our individual, brilliance.

The Seven Meanings of “Gene” 

During the twentieth century geneticists used at least five overlapping definitions of the gene:

1. Mendel’s: a gene is a unit of heredity, an archive for the storage of evolutionary information.
2. De Vries’s interchangeable part. The stunning surprise from the reading of genomes in the 1990s is that the human being has far more genes in common with the fly and the worm than anybody expected.
3. The English doctor Archibald Garrod’s one gene, one disease. This is misleading in two ways:
   1. It fails to mention that one mutated gene can be associated with many diseases, and one disease with many mutated genes; 
   2. It implies that the function of the gene is to prevent that disease. 
   3. The Garrodian gene is a disease averter, a health giver.
4. What it actually does. Genes have two jobs:
   1. Copying themselves 
   2. Expressing themselves through the construction of proteins.
   3. The Watson-Crick gene is a recipe.
5. Fransois Jacob and Jacques Monod: the gene as a switch and therefore as a unit of development. They discovered how a bacterium in a solution of lactose suddenly begins to produce the enzyme that enables digestion of lactose, and then stops making it when enough has been produced.
   1. Now known as promoters and enhancers, these switches are the key to the development of a body from an embryo.
   2. The result is that the same gene can be used in different species or in different parts of the body to produce completely different effects, depending on which other genes are also active.
   3. This is one reason that it is risky to speak of a “gene for” something: many genes have multiple jobs.

There were legions of scientists who used the word gene without meaning any of these five concepts. For them, the gene was not the unit of heredity, evolution, disease, development, or metabolism so much as it was the victim of selection.

People are instinctively nice to their children because their genes make them that way, and their genes make them that way because genes that do so survive – through the children – at the expense of genes that do not.

The beauty of Tooby and Cosmides’s gene: it integrates all the other six definitions and adds a seventh. 

1. It is a Dawkinsian gene with attitude (in its dependence on passing the test of survival through the generations); 
2. A Mendelian archive (inscribed with the wisdom derived from millions of years of evolutionary adjustment);
3. A Watson-Crick recipe (achieving its effects through the creation of proteins via RNAs);
4. A Jacob-Monod developmental switch (expressing itself only in precisely specified tissues);
5. A Garrodian health-giver (ensuring a healthy developmental outcome in the expected environment); 
6. A De Vriesian pangen (reused in many dif­ ferent developmental programs in the same species and in others). 
7. But it is also something else. It is a device for extracting information from the environment.

Genes themselves are implacable little determinists, churning out utterly predictable messages. But because of the way their promoters switch on and off in response to external instruction, genes are very far from being fixed in their actions. Instead, they are devices for extracting information from the environment. Every minute, every second, the pattern of genes being expressed in your brain changes, often in direct or indirect response to events outside the body. Genes are the mechanisms of experIence.

A Budget of Paradoxical Morals 

Moral I: Genes are enablers

Genes are enablers, not con­strainers. They create new possibilities for the organism; they do not reduce its options. These new possibilities are open to experience, not scripted in advance. Genes no more constrain human nature than extra programs constrain a computer.

Genes, unlike gods, are conditional. They are exquisitely good at simple if-then logic: if in a certain environment, then develop in a certain way.

Moral 2: Parents

Do parents have any important long-term effects on the development of their child’s personality? This article examines the evidence and concludes that the answer is no. 

• From about 1950 onward psychologists had studied what they called the socialization of children. 
• Although they were initially disappointed to find few clear-cut correlations between parenting style and a child’s personality, they clung to the behaviorist assumption that parents were training their children’s characters by reward and punishment, and the Freudian assumption that many people’s psychological problems had been created by their parents.
• Of course, children resemble their parents: they share many of the same genes. Once the studies of twins raised apart started coming out, proving dramatically high heritability for personality, you could no longer ignore the possibil­ity that parents had put their children’s character in place at the moment of conception, not during the long years of childhood.

The correlation of good parenting with certain personalities is worthless as proof that parents shape personality, because correlation cannot distinguish cause from effect.

Parents may reinforce nature with nurture, but they do not create the difference.

Moral: being a good parent still matters.

Moral 3: Peers

Harris’s believes that the environment, as well as the genome, has an enormous influence on the personality of a child, but mainly through the child’s peer group. Children do not see themselves as apprentice adults. They are trying to be good at being children, which means finding a niche within groups of peers-conforming, but also differentiating themselves; competing, but also collaborating.

Conformity is indeed a feature of human society, at all ages. The more rivalry there is between groups, the more people will conform to the norms of their own group. But under the superficial conformity in tribal costumes lies an almost frantic search for individual differentiation. 

Examine any group of young people, and you will find each playing a consistently different role: a tough, a wit, a brain, a leader, a schemer, a beauty. These roles are created by nature via nurture. Each child soon realizes what he or she is good at and bad at – compared with the others in the group. The child then trains for that role and not for others, acting in character, developing still further the talent he has and neglecting the talent that is lacking.

Small differences in innate character are exagger­ated by practice, not ironed out.

The Asterix theory of human personality: in Goscinny and Uderzo’s cartoons about a defiant Gaulish village resisting the might of the Roman empire, there is a very neatly drawn division of labor. 

The village contains a strong man (Obelix), a chief (Vitalstatistix), a druid (Getafix), a bard (Cacophonix), a blacksmith (Fulliautomatix), a fishmonger (Unhygienix), and a man with bright ideas (Asterix). The harmony of the village owes something to the fact that each man respects the others’ talents – with the exception of Cacophonix, the bard, whose songs are universally dreaded.

Specialization is useless without exchange. 

Nobody but a beggar chooses to depend chiefly upon the benevolence of his fellow-citizens.

Moral: individuality is a product of aptitude reinforced by appetite.

Moral 4: Meritocracy

The more egalitarian a society is, the more innate factors will matter.

Moral: egalitarians should emphasize nature; snobs should emphasize nurture.

Moral 5: Race

Within four minutes, the evolutionary psychologists had done what social science had failed to do in decades: make people ignore race. The way to do it is to give them another, stronger clue to coalition membership. 

• Sports fans are well aware of the phenomenon: white fans cheer a black player on “their” team as he beats a white player on the opposing team. 
• This study has immense implications for social policy.
  • It suggests that categorizing individuals by race is not inevitable, that racism can be easily defeated if coalition clues cut across races, and that there is nothing intractable about racist attitudes. 
  • It also suggests that the more people of different races seem to act or be treated as members of a rival coalition, the more racist instincts they risk evoking. 
  • On the other hand, it suggests that sexism is a harder nut to crack because people will continue to stereotype men as men and women as women, even when they also see them as colleagues or friends.

Moral: the more we understand both our genes and our instincts, the less inevitable they seem.

Moral 6: Individuality

The study makes clear that a “bad” genotype is not a sentence; for ill effects to occur, a bad environment is also required.
Likewise, a “bad” environment is not a sentence; it also requires a “bad” genotype if it is to produce ill effects.

Now that science knows the connection between gene and environment, ignorance is no longer morally neutral. Is it more moral to insist that all vulnerable people take such a test, to save them from future imprisonment, or that nobody be offered such a test?

Moral: social policy must adapt to a world in which everybody is different.

Moral 7: Free Will

Free will is the sum and product of circular influences with varying networks of neurons, immanent in a circular relationship between genes. 

• In Freeman’s words, “each of us is a source of meaning, a wellspring for the flow of fresh constructions within our brains and bodies.” 
• There is no “me” inside my brain; there is only an ever-changing set of brain states, a distillation of history, emotion, instinct, experience, and the influence of other people – not to mention chance.

Moral: free will is entirely compatible with a brain exquisitely prespecified by, and run by, genes.