"The phrase 'nature and nurture' is a convenient jingle of words, for it separates under two distinct heads the innumerable elements of which personality is composed."
        - Francis Galton, "English Men of Science: Their Nature and Nurture", 1874.


Prologue: Twelve Hairy Men
1. The Paragon of Animals
2. A Plethora of Instincts
3. A Convenient Jingle
4. The Madness of Causes
5. Genes in the Fourth Dimension
6. Formative Years
7. Learning Lessons
8. Conundrums of Culture
9. The Seven Meanings of 'Gene'
10. A Budget of Paradoxical Morals
Epilogue: Homo stramineus - the Straw Man


"There ain't nothing in the middle of the road but a yellow line and a dead armadillo."
        - Jim Hightower, Texan politician

Just 33 genes, each coming in just two varieties (such as on or off), would be enough to make every human being in the world unique. There are more than 10 billion ways of flipping a coin 33 times. So 30,000 does not look like such a small number after all.

If fewer genes meant more free will, that made fruit flies freer than people, bacteria freer still, and viruses the John Stuart Mills of biology.

The increasingly repetitive argument over environment versus heredity... with the possible exception of the Irish question, the intellectual argument that had changed least in the century just ended.

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, Kraeplin's history, Freud's formative experience, Boas's culture, Durkheim's division of labour, Piaget's development and Lorenz's imprinting.
They were right in the sense that the contributed an original idea with a germ of truth in it; they all placed a brick in the wall.

They are wrong only when they try to pull somebody else's bricks out, or to claim that the wall is held up only by their bricks.


"Frightful and painfully and disagreeably human."
        - Queen Victoria's description of an orang-utan in a zoo, 1843.

"The difference in mind between man and the higher animals, great as it is, is certainly one of degree and not of kind."
        - Charles Darwin

In 1871, Darwin drew up a list of human peculiarities that had been claimed to form an impassable barrier between man and animals. He then demolished each peculiarity one by one.

As Stalin is reputed to have said of military force, quantity has a quality all its own. We are so much better at language than even the cleverest ape that it really could be called a difference of kind, not degree. To concede that language is qualitative difference does not imply that we can set human beings apart from nature, though. Trunks are unique to elephants. Uniqueness is not unique.

So which are we, similar to apes or different from apes? Both.

Forty years of field primatology have confirmed that we are a unique species, completely unlike any other. There is no eact parallel to the human scheme. But in the animal kingdom, there is nothing exceptional in being unique. Every species is unique.

Anthropologists are fond of claiming an almost limitless diversity of behaviours in human cultures, but there is no human culture so extreme that it even begins to compare to the social system of either the chimpanzee or the gorilla.

The timely discovery of bonobo sex lives had made them into the latest animal celebrities, supplanting the dolphins which had rather blotted their eco-friendly image by indulging in something that looks very like kidnapping and gang rape.


"When, as by a miracle, the lovely butterfly bursts from the chrysalis full-winged and perfect... it has, for the most part, nothing to learn, because its little life flows from its organization like medlody from a music box."
        - Douglas Alexander Spalding (1873)

Both James brothers were influenced by Darwin. Henry's novel, 'The Portrait of a Lady' was written in thrall to Darwin's idea of female choice as a force in evolution... William James believed that human beings were equipped with innate tendencies that were not derived from experience but from the Darwinian process of natural selection.

When a person who says she (or he) is in love contemplates a picture of her loved one while sitting in a brain scanner, certain parts of her brain light up that do not light up when she looks at a picture of a mere acquaintance. Those brain parts overlap with the ones stimulated by cocaine.

All this could be a coincidence, and human love may be entirely different from rodent pair-bonding, but given how conservative the Genome Organizing Device (GOD) is and how much continuity there is between human beings and other animals, you would be unwise to bet on it.

The point of dogs is that they come in different behavioural types: retrievers, pointers, setters, shepherds, terriers, poodles, bulldogs, wolfhounds - their very names denote the fact that they have instincts bred into them. And those instincts are innate.

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.

Culture will often reflect human nature rather than affect it.

In one study, Jennifer Connellan gave 102 24-hour-old babies two things to look at: her own face, or a physical-mechanical mobile of approximately the same size and shape as a face. The baby boys slightly preferred to look at the mobile; the baby girls slightly preferred the face.


"Professors are inclined to attribute the intelligence of their children to nature, and the intelligence of their students to nurture."
        - Roger Masters

Heritability is a measure of what is varying, not what is determining.

In a true meritocracy, where all have equal opportunity and equal training, the best athletes will be the ones with the best genes. Heritability of athletic ability will approach 100%. In the opposite kind of society, where only privileged few get sufficient food and the chance to train, background and opportunity will determine who wins the races. Heritability wil be zero. Paradoxically, therefore, the more equal we make society, the higher heritability will be, and the more genes will matter.

It occured to Tom Bouchard that maybe twins reared apart would turn out not just as similar, but maybe
more similar than twins reared together. In the same family, differences might become exaggerated. This is now known to be true. Twins who were separated early in life, have more similarities than twins separated at a later age.

Personality is about as heritable as body weight. The correlation between siblings in weight is 34%. The similarity between parents and children is a little lower, at 26%. Identical twins reared in the same family have a correlation of 80% while fraternal twins reared together have only 43% similarity, which suggests that genes matter more than shared eating habits. What about adoptees? The correlation between adoptees and their adoptive parents is only 4%, and between unrelated siblings in the same family it is just 1%. By contrast, identical twins reared apart in different families are still 72% similar in weight.

I suspect if you took a poll of ordinary people, they would hardly have changed their views over a century. Most people believe in 'intelligence' -  a natural aptitide or lack of it for intellectual pursuits.

By adulthood, intelligence is like personality: mostly inherited, partly influenced by factors unique to the individual and very little affected by the family you grew up in. This is a counter-intuitive discovery exploding the old idea that genes come early and nurture late.

The 'environment' is not some inflexible and real thing: it is a unique set of influences actively chosen by the actor himself. Having a certain set of genes predisposes a person to experience a certain environment.

The genes are likely to be affecting appetite more than aptitude. They do not make you intelligent; they make you more likely to enjoy learning. Because you enjoy it, you spend more time doing it and you grow more clever. Nature can only act via nurture. The environment acts as a multiplier of small genetic differences, pushing sporty children towards the sports that reward them, and pushing bright children towards the books that reward them.

Something about modern life, whether it is nutrition, education or mental stimulation, is making each generation better at IQ tests than its parents. Therefore, said one or two nurturists triumphantly, the role of genes must be smaller than though. But the anaology of height shows what a non sequitur this is. Thanks to better nutrition, each generation is taller than its parents, but nobody would argue that therefore height is less genetic than was thought. In fact, because more people now reach their full potential stature, the heritability in height is probably increasing.


"The word 'cause' is an altar to an unknown god."
        - William James

What is a cause anyway? The causes of human experience include genes, accidents, infections, birth order, teachers, parents, circumstance, opportunity and chance, to name just the most obvious.

When you catch a cold the chief cause is a virus, but when you catch pneumonia the bacterium is only an opportunist, your immune system usually needs to be run down first by starvation, hypothermia or stress. Is that the 'true' cause?

Perhaps all we inherit is a susceptibility, just as some people inherit a susceptibility to hay fever - but the cause of hay fever is surely pollen... Having the predisposing genes is necessary, but not sufficient, to develop the disorder.

The virus that causes AIDS is a retrovirus, which means that when you catch AIDS, the genes of the virus are literally incorporated into the DNA in the chromosomes of some of your blood cells.

"I have been surprised at finding by how often insanity has appeared among the near relatives of exceptionally able men."
        - Francis Galton

Such an argument led Henry Maudsley to reject eugenics, because he realised that sterilising those with a taint of mental illness would wipe out a lot of geniuses, too.

The Michigan psychiatrist Randolph Nesse specualtes that schizophrenia may be an example of an evolutionary 'cliff effect', in which the mutations in different genes are all beneficial, except when they all come together in one person, or evolve just too far, at which point they combine to produce a disaster.

During the 20th century, the ideological forces of nature and nurture often behaved like medieval armies laying siege to diseases as if they were castles. Scurvy and pellagra, explained as vitamin deficiencies, fell to the forces of nurture, while haemophilia and Huntington's, explained as genetic mutations, fell to the army of nature.


The comforting belief that nurture is more malleable than nature relies partly on the fallacy that nurture is what happens after birth and nature is what happens before birth. Fallacy it is.

If the influence of the environment is partly prenatal, then the environment begins to sound a lot less like a malleable force and more like fate.

In 1989, a medical scientist named David Barker analysed he fate of more than 5,600 men born between 1911 and 1930 in six districts of Hertfordshire in southern England. Those who had weighed the least at birth and at one year old went on to have the highest death rate from ischaemic heart disease. The risk of death was nearly three times as great in the light babies as in the heavy babies.
Barker has gone on to confirm the same result in data from other parts of the world for heart disease, stroke and diabetes.

According to the 'thrifty phentotype' hypothesis, which has grown out of this work, Barker has found an adaptation to famine. A poorly nourished baby's body, imprinted with its prenatal experience, is born 'expecting' to live in a state of food deprivation throughout its life. Its whole metabolism is geared to being small, hoarding calories and avoiding excessive exercise. When, instead, the baby finds itself in a time of plenty, it compensates by growing fast but in such a way as to put a strain on its heart.

This bizarre second-generation effect is hard to explain with the thrifty phentotype hypothesis, though Pat Bateson notes that locusts take several generations to switch from the shy, solitary form with a  specialist diet to the swarming, gregarious form with a generalist diet and back again.
If it takes several generations for humans to switch between thrifty and affluent phenotypes, this may explain why Finland has nearly four times the death rate from heart disease as France. The people of Finland lived in comparitive poverty until 50 years ago. Perhaps it is the first two generations to experience abundance who suffer from heart disease.

It has long been clear from the experiences of homosexual people that human sexual preferences are not only difficult to change, but also fixed from a very early age. Nobody in science now believes that sexual orientation is caused by events in adolescence. Adolescence merely develops a negative that was exposed much earlier.
Homosexuality is an early, probably prenatal and irreversible preference.

Language does not just develop according to a genetic programme. Nor is it just absorbed from the outside world. Instead it is imprinted. It is a temporary innate ability to learn by experience from the environment, a natural instinct for acquiring nurtue. Polarise that into either nature or nurture, if you can.

Biology, someone once said, is the science of exceptions, not rules.


Snake-fear is one of the commonest forms of phobia. Coincidentally, many people report that they gained their fear by a vicarious experience, such as seeing a parent react with fear to a snake. People are also commonly afraid of spiders, the dark, heights, deep water, small spaces and thunder. All of these were a threat to Stone Age people, whearas the much greater threats of modern life - cars, skis, guns, electric sockets - simply do not induce such phobias.

It defies common-sense not to see the handiwork of evolution here: the human brain is pre-wired to learn fears that were of relevance in the Stone Age. And the only way evolution can transmit such information from the past to the design of the mind in the present is via the genes. That is what genes are: parts of an information system that collects facts about the world in the past and incorporates them into good design for the future through natural selection.

Of course, I cannot prove the last sentences... I just cannot think of a better explanation.

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


"Some men by the unalterable frame of their constitutions, are stout, others timorous, some confident, others modest, tractable, or obstinate, curious or careless, quick or slow."
        - John Locke, "Essay on Human Understanding", 1692.

An ordinary businessman could not do without the help of Assyrian phonetic script, Chinese printing, Arabic algebra, Indian numerals, Italian double-entry book-keeping, Dutch merchant law, Californian integrated circuits, and a host of other inventions spread over continents and centuries. What is it that makes people, and not chimps, capable of this feat of accumulation?

A truly extraordinary idea has begun to take shape in the minds of several different scientists in recent years. They are beginning to suspect that human language was originally transmitted by gesture, not speech.

A hint of the primacy of sign language comes from the human capacity for expressing language through the hands rather than the voice... just as spoken pidgins can be turned into fully grammatical creoles only when learned by a generation of children, so the same has proved true of sign languages.
As final proof of the fact that speech is just one delivery mechanism for the language organ, deaf people can become manually 'aphasic' when they have strokes that affect the same regions of the brain as hearing people.

One of the beauties of the gesture theory is that it immediately suggests why human beings got language and other apes did not. Bipedalism freed the hands not just to carry things, but to talk.

The attributes of speech appear so late that some anthropologists have been tempted to infer that language was a recent invention, appearing as little as 70,000 years ago. But language is not the same thing as speech: syntax, grammer, recursion and inflection may be ancient, but they may have been done with hands, not voice.

"Human history involves the playing of ever more numerous, ever larger and ever more elaborate non-zero-sum games."
        - Robert Wright, "Nonzero"

Robert Wright concludes that human density played a part in human destiny. Once the continents were populated, albeit sparsely, and people could no longer emigrate to empty territory, density began to rise in the most fertile areas. With rising density came the possibility - nay, the inevitability - of increasing divisions of labour and therefore increasing technical invention.

So long as human beings lived, like other apes, in separate and competing groups, swapping only adolescent females, there was a limit to how rapidly culture could change, however well equipped human brains were to scheme, to woo, to speak or to think, and however high population density was. New ideas had to be invented at home, they could not generally be brought in. Successful inventions might help their owners to displace rival tribes and take over the world. But innovation came slowly. With the arrival of trade - exchange of artefacts, food and information initially between individuals and later between groups - all that changes. Culture could evolve.

Exchange plays the same role in cultural evolution that sex plays in biological evolution. Sex brings together genetic innovations made in different bodies; trade brings together cultural innovations made in different tribes.


Edward O. Wilson first found William Hamilton's scientific paper naive and foolish and tossed it aside after a cursory read, but he could not quite pin down its flaw. By the time his train was passing through New Jersey, he was rereading the paper more carefully. In Virginia he was frustrated and angry at Hamilton's presumption. Into northern Florida and Wilson was weakening. By the time he reached Miami, Wilson was a convert.

Wilson (after publishing 'Sociobiology) had encountered exactly the same wounded pride that had met Copernicus and Darwin: human beings do not enjoy seeing themselves dethroned from the centre of the universe. To see human behaviour dethroned from its supremacy and described in the same terms as ant behaviour was as insulting to the pride of the species as to see the Earth demoted to a planet.

Risk-taking is in the male essence - though it can be tempered by culture, varied by individuality and muted by technology.


"Why wrestle with Kant's God, Freedom and immortality when it is only a matter of time before neuroscience, probably through brain imaging, reveals the actual physical mechanism that fabricates these mental constructs, these illusions?"
        - Tom Wolfe, "Hooking Up" (2000)

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. I suspect science has so far greatly underestimated the number of gene sets that act in this way - conditioning their output to external conditions.

Stephen Suomi's colleagues have since gone on to study the serotonin transporter gene in monkeys. One version of the gene produces a powerful and long-lasting reaction to maternal deprivation, whearas the other version of the gene is immune to materal deprivation. Since this gene also varies in human beings and the variation correlates with personality differences, this is a big finding. Translated into human terms it would imply that some children can be virtually orphaned and are none the worse for it; others need to be very well nurtured by their parents to turn out normal - the difference lies in the genes. Did we ever expect differently?

Children do not see themselves as apprentice adults. They are trying to be good at being children, with means finding a niche within groups of peers - conforming, but also differentiating themselves; competing, but also collaborating. They get their language and their accents largely from their peers, not their parents.

Most people think of peer pressure as pushing the young towards conformity. Conformity is indeed a feature of human society, at all ages. But there is something else going on beneath the surface. Under the superficial conformity lies an almost frantic search for individual differentiation. Examine any group of young people and you will find each playing a consistently different role. There is a tough, a wit, a brain, a leader, a schemer, a beauty. These roles are created, of course, by nature via nurture. Each child soon realises what he or she is good at and what he or she is bad at - compared with others in the group. He then trains for that role and not for others.
This is true within families as well as in school classes and street gangs.

This tendency to differentiate first emerges about the age of eight.

It is, I suggest, an instinct peculiar to human beings, deposited in the adolescent human brain by natural selection over tens of thousands of years, and it simply whispers in the ear of the juvenile: Enjoy doing what you are good at; dislike what you are bad at.

Every job interview is about genetic discrimination... unless she is prepared to go on qualifications and experience alone - in which case, why hold an interview? - then she is looking for some intrinsic, rather than acquired talent. The more she is prepared to make allowances for a deprived background, the more of a genetic determinist she is. Besides, the other point of the interview is to take into consideration personality, and remember the lesson of twin studies: personality is even more strongly heritable in this society than intelligence.

Welcome to the first of many Promethean dilemmas for the new century.

Social policy must adapt to a world in which everybody is different.

The only difference between a human being and a stone rolling down a hill is that the human being thinks he is in control of his own destiny.
        - Spinoza

An animal determined 99% by genes and 1% by its own agency has more free will than one determined 1% by genes and 99% by nurture.
        - Henrik Walter


Instead of a steady progress towards englightenment, the 20th century became a collision of ideas, a hundred years war between the forces of nature and the forces of nurture. Anthropology was its Flanders, Harvard its Manassas, Russia its Russia. Too many slipped into the false equation that to prove one proposition right was to prove another wrong - that success for nature could only mean defeat for nurture, and vice versa.

I hope I have shown that the more you discover genes that influence behaviour, the more you find that they work through nurture, and the more you find that animals learn, the more you discover that learning works through genes.

Nature versus Nurture is dead. Long live nature via nurture.

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