My attention was drawn to a recent rant against the role genes play in human behaviour, by the psychologist Oliver James, by a rebuke, yesterday, from two prominent scientists working in the area of genomics and neurobiology, Chris Ponting and Keith Talbot.
James had blithely asserted that there has been a shambolic and wholesale retreat from the role genes play in determining our behaviour, ever since the human genome was fully published some nine years ago. He misunderstands comments made by Craig Venter regarding the way in which genes can or cannot have an impact on the human brain in the light of the discovery that there are "only" 25,000 working genes in the human genome; suggests that research into the genetic component of ADHD has run into the sand; and sounds the death knell for theories that genes can contribute to human behavioural traits by applauding a meta-analysis by Risch, in JAMA last year, that could not uphold the results of earlier longitudinal studies on the role short variants of the serotonin transporter gene have on depression. I've linked to James' original article and here is the riposte:
Letters
Genetic contribution to human behaviour
The Guardian, Thursday 28 January 2010
In his latest rant against genetics, Oliver James either does not understand, or wilfully misunderstands, the genetic basis of neurobiology, and purposefully overlooks huge swathes of scientific literature (Nature v nurture – what are the latest genetic findings, 23 January).
Despite the enormous complexity of the human genome, geneticists are continuing to reveal many DNA changes that explain disorders such as learning disability and autism. These changes are often private to each individual. This tells us that different parts of the human genome can be disrupted independently in people with a single disease: there are likely to be many dozens, possibly hundreds, of "autism genes", for example.
It is, indeed, "extremely unlikely that there are single genes for major mental illnesses such as schizophrenia" but this does not indicate that genetics play no part. Like the brain itself, the genetic contribution to behaviour is complex.
This is not a "fallback position", but a straightforward and dispassionate appraisal of the facts. Far from having "to admit defeat", geneticists have begun to disperse the fog that has enveloped genetic disease. Their new insights should ensure that unwarranted pronouncements of fault are not levelled at parents who produce anyone other than a "normal" child.
Chris Ponting
Medical research council and professor of genomics, University of Oxford
Kevin Talbot
Reader in the department of neurology, University of Oxford
Dear reader make what you will of James' target article. He has for years fought against the idea that genes play a prominent role in the development of human behavioural traits and is fond of exclusively stressing "the environment" and, therefore, the unique plasticity of human mental traits. I consider him to be a stupid and wilfuly ignorant commentator, as do Ponting and Talbot, and anyone who has ploughed through the genetics chapters in NOT A CHIMP will, I hope, be convinced that - to the contrary of James' assertions - the last nine years have uncovered a host of genetic mechanisms, and structural features of the human genome, that have sculpted our brains and cognition over the last six million years. However, the Risch findings do deserve further comment. You can access a careful and balanced report on them, by Bruce Bower, at:
http://www.sciencenews.org/view/generic/id/44733/title/Gene_plus_stress_equals_depression_debate
As Bower points out, Caspi and Moffitt, the authors of the longitudinal Dunedin study, mentioned by James and covered in the penultimate chapter of NOT A CHIMP, mount a solid defence against the negative findings of Risch's meta-analysis, which took into consideration a number of larger studies done with much less satisfactory measures of depression etc. than the Dunedin study. Moreover, as I reported, James ignores, or does not know about, the numerous pieces of scientific work on normal volunteers which links variants in MAO and serotonin transporter genes to hyper-vigilance and depression, and poor coupling between amygdala (the brain's fear centre), the anterior cingulate cortex, and the frontal lobes of the brain.
James concludes thus: "In Darwinian terms, it has always made much more sense that we should be born plastic. Obviously, genes confer fundamentals, such as the capacity for humour or anger, but how much we express these is in response to our particular FAMILY situation, for which we need flexibility, not predetermination. if genes play little part in how our children turn out, that is incredibly good news. Unlike our DNA, we can do something about them."
The obvious point is that the action of genes in the brain does not imply predetermination of behaviour, and the fine and intricate nature - through numerous mechanisms - of control of gene expression actually creates the flexible engine James searches for. Genes DO play a fundamental part in who and what we are as advanced cognitive animals. Generations of parents who have brought up several children apiece know full well, from individual differences and their attempted effects on outcomes, the role that genes play in the development of mental traits in all of us. Their experiences reveal James' smugness for what it is - a deliberate "one eye shut" approach to the evolution and expression of human functional neurobiology. Exclude the subtle nature of gene-environment interaction, and the co-evolution of genes and environment at your peril - you will dance witlessly around the enigma of human behaviour for ever.