Nature v nurture? Please don't ask

[Guest guest]

http://www.timesonline.co.uk/tol/news/uk/science/article5986239.ece

Nature v nurture? Please don't ask

The question has fuelled some of history's fiercest scientific and political

feuds. Now we have an answer

March 28, 2009

Mark

The monster Caliban, according to his master, Prospero, was " a devil, a pure

devil, on whose nature nurture can never stick " . Yet only a few decades before

Shakespeare wrote The Tempest, St Ignatius Loyola had founded the Jesuit order,

with its famous maxim: " Give me the child until he is 7, and I will show you the

man. "

This ancient debate over the relative contributions of inheritance and

experience to the human condition has never been more charged than in the

genetic age. On one side stood those who sought and saw genetic explanations for

human psychology; on the other, those who believed it to be moulded by culture.

There was little common ground. Blaffer Hrdy, an evolutionary

psychologist, has even joked that perhaps we are genetically programmed to set

nature against nurture.

Since the middle of the last century the nurture camp has been dominant. Just as

molecular biology began to unravel the secrets of DNA, genetics and evolution

were relegated to psychological bit-players by a new orthodoxy, which held that

biology has forged a human mind of almost limitless malleability. It was the

doctrine of the blank slate.

The idea, usually traced to the 17th-century philosopher Locke, grew

popular in the Enlightenment, fitting the mood of challenge to the supposedly

innate authority of monarchy and aristocracy. It was a statement of individual

freedom, which became strongly associated with the political Left. Though many

early socialists were enthusiasts for eugenics, later generations grew

suspicious of genetics, particularly after it was abused to justify oppression

of disadvantaged racial and social groups, most brutally in Nazi Germany.

Liberal opinion turned against the concept of a biological human nature, which

was increasingly seen as a tool with which male and bourgeois elites could

rationalise hegemony.

The movement was driven by the social sciences. From psychology came Sigmund

Freud's notion that attitudes and mental health are explained by childhood

experience. The behaviourism of B.F.Skinner added the claim that human beings

could be conditioned by training, much as Ivan Pavlov's celebrated dogs

salivated at the sound of a bell.

From anthropology came the research of Franz Boas and Margaret Mead, whose

comparative studies of different societies suggested that traditions could steer

human behaviour in a multitude of directions. Mead's purported discovery of free

love among Samoan women was influential because - though founded on poor data -

it challenged prevailing sexual mores. Karl Marx's political and economic

theories saw human nature as something to be reshaped and directed to facilitate

revolution. And postmodernism contributed the mantra that even knowledge and

truth are socially constructed and relative.

What emerged was a new model of behaviour, in which human nature is anything but

fixed or shared, but can be moulded into many configurations by culture. If

genetic influences are allowed at all, they are wholly secondary to those of the

environment. To its supporters, this became axiomatic to a fair society: if

anything can be learnt, and anybody can do the learning, then people can be

taught to value equality. Social justice and morality became intertwined with

the concept that little in life is laid down, or even much affected, by

inherited genes.

Though well-intentioned, and in some respects an important antidote to

pseudoscientific genetic determinism, this view was dangerously inflexible. Any

evidence that genetics might be seriously influential after all would threaten

the very foundations of liberty and equality - so it would have to be resisted,

as would research that might provide it.

The result was that scientists who investigated effects on human behaviour found

their positions caricatured and their politics demonised as reactionary, even

fascist. E.O., the great evolutionary theorist and conservationist, is no

man of the Right. Yet when he dared in the 1970s to suggest that human nature,

like that of other animals, has a biological basis that might fruitfully be

studied, his lectures were picketed and students doused him with water. The

left-wing biologists Rose, Leon Kamin and Lewontin responded with

a book entitled Not in Our Genes, which accused , Dawkins and

other sociobiologists of a crude determinism designed to legitimise the status

quo. " Its adherents claim, first, that the details of present and past social

arrangements are the inevitable manifestations of the specific action of genes, "

they wrote.

Such attacks were misconceived. First, as Pinker has pointed out, they

set up a straw man. It is simply impossible to find serious biologists who

believe that behaviour and social structure are " the inevitable manifestations

of the specific action of genes " . Those who reject cultural determinism make a

much more modest proposal - that genes, as well as the environment, make a

contribution. As Dawkins wrote in a review of Not in Our Genes: " Reductionism,

in the `sum of the parts' sense, is obviously daft, and is nowhere to be found

in the writings of real biologists. "

What is more, cultural determinism can be just as inimical to freedom as its

genetic counterpart. It implies that instead of being prisoners of our genes, we

are prisoners of our parents, teachers and societies. Those who grow up in

poverty will be forever disadvantaged, while those who come from privilege will

retain it. Autism can be blamed on " refrigerator mothers " , and adults'

relationship problems on their overprotective families. As a world view it is

quite as bleak as one based on inheritance.

It has also become scientifically unsustainable. As research reveals more about

inheritance, it has become abundantly clear that humans are not blank slates.

Neither, however, are our personalities and behaviour forged by genes alone. The

great controversy, indeed, is giving way to consensus, as improved understanding

of how genes actually work shows the difficulty of separating nature and

nurture.

Much of the critical evidence has emerged through the study of twins. Identical

twins share all their DNA, while fraternal twins share only half - they are no

more closely related on a genetic level than are ordinary siblings. Both kinds

of twins, however, share a womb, a family and a cultural environment.

Comparisons between the two types can thus tease out the extent to which

inheritance is important.

Across a wide range of traits, including IQ, personality indicators such as

extroversion and neuroticism, and even homosexuality, religiosity and political

conservatism, identical twins are more similar to one another than are fraternal

pairs. This indicates that genes must affect these aspects of personality.

The concordance between identical twins, however, is rarely 100per cent - their

IQ scores, for example, tend to be around 70 per cent similar, compared with

around 50per cent for non-identical pairs. By definition, inheritance therefore

cannot be the only factor involved: if it were, identical twins would always

turn out the same. For most human qualities, neither the extreme-nurture nor the

extreme-nature hypothesis can be correct.

Even more striking evidence has come from a recent series of studies led by

Avshalom Caspi and Terrie Moffitt. These scientists have been following up a

cohort of children born in 1972-73 in Dunedin, New Zealand, recording details of

their life experiences and testing their DNA. The results have demolished the

nature- nurture dichotomy.

First, Moffitt and Caspi studied a gene called MAOA, which has two variants or

alleles. Boys with one allele are more likely to behave antisocially and get

into trouble with the law - but only if they were also maltreated as children.

When raised in well-adjusted families, those with the " risky " allele are fine.

It is not a gene " for " criminality, and no determinism - genetic or

environmental - is involved. A genetic variant must be activated by an

environmental influence to do any potential harm.

The serotonin transporter gene, 5HTT, also has two alleles, and is known to be

involved in mood. Moffitt and Caspi found that people with one allele were 2.5

times more likely to develop clinical depression than those with the other -

but, again, only under particular circumstances. The risk applies only to people

who also experience stressful life events such as unemployment, divorce or

bereavement. When their environments are happy, their genotypes made no

difference.

These results show the sterility of the old nature-nurture debate. Nature works

through nurture, and nurture through nature, to shape our personalities,

aptitudes, health and behaviour. The question should not be which is the

dominant influence, but how they fit together.

[Guest guest]

I've been saying this for a long time. It is amazing how many human arguments get polarized between two main points and nothing gets resolved. In the case of nature vs. nurture it is clearly not either/or but more of a spectrum

For example:

Some people, no matter how good their nurture will be evil while on the other hand, some, no matter how bad their nurture will rise above it.

As a spectrum, nature will influence some more than others and likewise nurture will affect some more than others. A person very good by nature could be corrupted by bad nurture.

This could be something very long, but suffice it to say: both forces have an affect on people though the balance varies by person.

We can see this with AS. Children raised in supportive homes with supportive education systems where they aren't bullied too much and learn to compensate for their difficulties can go on to have spectacular lives. ON the other hand, if they are bullied at home and school, the school doesn't care about them and just chucks them in special ed and neglects them, they the odds that they will have a bad outcome is much higher.

Likewise, friendly and kind people can be beaten down into a misanthropic recluse because of years of negative nurture at the hands of others.

In a message dated 3/28/2009 11:12:56 A.M. Eastern Daylight Time, no_reply writes:

These results show the sterility of the old nature-nurture debate. Nature works through nurture, and nurture through nature, to shape our personalities, aptitudes, health and behaviour. The question should not be which is the dominant influence, but how they fit together. Feeling the pinch at the grocery store? Make dinner for $10 or less.

[Guest guest]

" Likewise, friendly and kind people can be beaten down into a misanthropic

recluse because of years of negative nurture at the hands of others. "

All good points. Lately I feel this way.

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