Gill Norman reviews Matt Ridley’s lecture given as part of the first
Centre for Life, 14 April 2003.
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Psychologists attend lectures on the Nature/Nurture
debate with a certain sense of weary inevitability. This is born of the
artificial polarisation of the debate by those with a book to sell or an axe to
grind. When I realised that
Matt Ridley had, yes, a new book to promote, I
settled down for a rehash of the old arguments. It was therefore delightful to
hear a speaker who articulated a balanced position in a novel way. This was
backed by evidence guaranteed to interest a wide range of biological scientists
as well as the general public.
The history of the debate
We started with a sweep through the history of the
debate, from both a literary and a philosophical viewpoint, which stressed that
it has been an issue for writers and educators as far back as the sixteenth
century. After a sweep through the derivation of what Galton termed "A
convenient jingle of words", and the philosophical divide between the
empirical school, represented by Locke, Hume and Mill (Nurture) and the
continental naturists such as Hobbes, Rousseau and Kant (Nature), we settled
down to a history of the science behind the debate in the last two centuries.
While the division of the last 130 years into blocks in which one viewpoint was
dominant was a little simplistic, it was nonetheless effective in conveying the
fluctuation of scientific fashions in this area, and hinting at the sometimes
dreadful political consequences of these skewed beliefs.
First he outlined the period 1870-1920 as "Heredity’s
Heyday" which began with Darwin, who wished to emphasise the shocking new
truth that humans were part of the animal continuum, touched on Galton and
William James and ended with Haeckel’s alarming theories on racial determinism.
We then heard the period of 1910-1960 characterised as years in which the view
of the child at birth as a tabula rasa or "Blank Slate" was current.
In this area psychologists were as dominant as biologists had been over the
previous half century, with a coherent case being made for the linking of Freud
with Pavlov and the founders of behaviourism, Watson and Skinner. The case for
the human as the product and not the cause of society had never been stronger.
Next he outlined the most recent period of 1960-2000 as
representing yet another swing of the pendulum. Following the discovery of
DNA’s structure in 1953 - an anniversary commemorated in this series of lectures
- evidence appeared to accumulate which pointed to innate components of
extremely complex behaviour, resulting in the current climate of headlines
reporting the discovery of "genes for criminality." The work of
Konrad Lorenz, Noam Chomsky and Jane Goodall was all placed in the context of
this argument for the innateness of much that makes us human - love, language
and society. Finally we were brought right up to date with the selfish gene
views propounded by Hamilton, Pinker, Boucher and Dawkins, for whom the body is
merely the vehicle that genes employ to reach the next generation.
The impact of genetic discoveries: Nature via nurture
In the year in which the complete human genome has
finally been published there was a timely examination of what this vast
potential knowledge might mean for the issue of what makes us who we are. The
idea that our unique consciousness and use of language resulted from having many
more genes than other organisms - perhaps as many as 100,000 - has been
exploded. The total is only 30,000, about the same as mice and a quarter less
than rice. Are there therefore too few genes to explain the complexity of human
behaviour, bringing nurture back into the picture by default? Is free will in
fact the null hypothesis? The idiocy of this philosophy of numbers was sharply
pointed up by the pithy observation that, under such a schema the virus would be
the J.S. Mill of biology!
The aim of this lecture, after all the scene-setting, was to
propound a view which integrates both nature and nurture into a single model.
As he pointed out at the beginning of the lecture, as long ago as 1581 Richard
Mulcaster wrote "By nature emplanted, for nurture to enlarge" and it
is this which forms the basis of his model. However, as well as including the
widely recognised feed-forward moderation of the relationship between phenotype
and behaviour by nurture, his model also included the feedback mechanism whereby
behaviour itself modifies the relationship between the genotype and the
phenotype. This incorporates the bi-directional relationship between behaviour
and gene expression which is widely acknowledged but rarely stated explicitly in
general texts. The neat title of the lecture "Nature via Nurture" was
thus arrived at.
The supporting evidence
The remainder of the lecture expounded this thesis with
reference to various examples in which the interaction of genes and experience
is observed. An excellent slide clearly illustrated the absurdity of the
"gene for every trait" approach often found in populist science
reporting. This purported to illustrate the genes for attributes of maleness,
which would of course be found on the Y-chromosome. After skimming down the
slide, from the gene for the tendency to play air guitar (RIF) past selective
hearing loss (HUH) to the love of gadgetry (MAC locus) the audience, or at least
that portion of it without a Y-chromosome, chuckled appreciatively.
More seriously, he cited the work of Susan Mineka and
colleagues, which provides a neat illustration of Seligman’s preparedness
theory whereby a predisposition to a particular behaviour is mediated by a
particular experience. In Mineka’s elegant study, a captive-bred monkey with no
fear of snakes in shown a videotape of a wild monkey showing terror in response
to a snake. The captive-bred animal developed an extreme fear of snakes
following the viewing - a clear example of vicarious conditioning. The
important element of the study, however, is the control condition, in which the
captive-bred monkey sees a videotape of the same monkey showing the same fearful
reactions to a flower. This fails to induce a fear of flowers in the subject
monkey, demonstrating that there must be both nature (tendency to fear snakes)
and nurture (experience of other animals showing fear) for conditioning to
Moving to humans, he cited walking and adoption of gender
roles as examples of behaviours which contain strong genetic components (all
infants pull themselves up and attempt to walk; boys are more likely than girls
to prefer war games) but also require experience (those wobbly steps need
practising; boys are more likely than girls to be praised for "tough"
behaviour). He is clearly on more controversial ground with the second example
than the first, but the point is well made and accessible.
When experience matters
The importance of experience and behaviour in guiding the
expression of genes is well illustrated by the examples of critical periods
presented here. At a very biological level we have the development of ocular
dominance columns in striate cortex which occurs during the first few days of
life in mammals. If visual input is absent or comes from only one eye, then
this organisation of the brain will not take place and the input from one eye
will be permanently disregarded by the brain. The genes determine the
organisation but the experience of vision is required for translation of
genotype to phenotype - the calibration of the system. The timing of the
critical period is known to be affected by a number of genes. For example, a
knockout of the GAD2 gene delays it indefinitely, whilst the genetically caused
over-expression of a nerve-growth factor (BDNF) causes the premature ending of
the critical period.
The imprinting which Lorenz used as such a powerful example
of biologically determined behaviour also turns out to have a critical period in
which it will occur, and when we turn to humans we find that one of our defining
features, language, also has a critical period for development. This is
illustrated by the sad examples of children who have been profoundly neglected
and deprived of spoken language input, such as Genie. Up until the age of about
13 it appears possible for language to be acquired, but after this point, though
words may be acquired, grammar will elude the child. Chomsky’s grammar may be
universal but it is not unlimited.
Staying with language, studies of a large family, many of
whose members suffer from specific language impairment (SLI) have identified a
gene which appears to be important in language development. SLI sufferers have
problems with language such as inability to generalise grammatical rules. The
members of this family with the problem also carried a mutation of the FOXP2
gene. This gene appears in a different form in humans to all other primates and
mammals. It has undergone two non-silent mutations in the last 200,000 years of
the human lineage which appear to have been very actively selected for. This may
be the gene for complex language but we need to remember that without experience
at the correct time it is never fully expressed.
Sex and Violence
There was some interesting speculation on the role of the
AVPRIA gene which is a vasopressin regulator. An insertion on this gene causes
vasopressin to be expressed in different regions of the brain. Both the
insertion and the differential expression of vasopressin are found in prairie
voles which form pair bonds which involve paternal involvement with offspring.
Neither are found in other vole species in which paternity begins and ends with
conception. Humans carry a similar insertion in the AVPRIA gene to prairie
voles, but there are substantial individual differences in the length of the
gene. Whether this is a factor in the formation of stable relationships is
clearly a question for future research . . . and a whole new section on the dating
Finally the issue of criminality was addressed. The question
of whether criminals are born or made has influenced penal policy for centuries,
and the answer would appear to be that both genes and childhood maltreatment are
vulnerability factors for a criminal record. While a Dutch family with a history
of antisocial behaviour in its male members showed a specific mutation in the
gene for monoamine oxidase A (MOA-A), an enzyme which breaks down the
neurotransmitter serotonin in the brain, this mutation has never been found
outside of this particular family. However, there are two forms of the promoter
for this gene, one highly active and the other less so. The genes themselves
have no impact on behaviour, but the combination of a less active MAO-A promoter
and childhood maltreatment produces a hugely increased risk of criminal
A Balanced View
The point was made that the best predictor of an outcome
will depend on the prevalence of both the gene and the behaviour: when few
people read behaviour is the best predictor of myopia, with mass education genes
become a better predictor. Matt Ridley never allows speculation to run away with
him, and just as we were tempted down the "Aha! A gene for . . ." route,
the evidence for the critical role of nurture was presented as a counterbalance.
The role of genes in permitting learning and the equal role of experience in
altering gene expression were repeatedly emphasised and made accessible through
One of the themes of this lecture, which made it stand out
from many such contributions was that it did not shy away from the
philosophical, and indeed theological implications of the viewpoints discussed.
As well as facing the issue of biological determinism head-on, even in the
controversial area of sex differences, Matt Ridley pointed out in his
conclusions what many social learning theorists fail to acknowledge: that social
determinism is just as inimical to free-will as the genetic kind. Leibniz’s
monads were experiential as well as biological and Freud was a determinist to
just as great an extent as Chomsky. The unfashionable truth that meritocracy is
genetic determinism was clearly stated, while evolution, and beyond that
technology, was identified as the greatest promoter of free-will. Stephen Fry,
who suggested that he call his book "Nature, Nurture and Nietzsche"
would not have been disappointed.
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