06 December 2010
ByAppeared in BioNews 587
Nature, Nurture or Neither? The View from the Genes
Organised by the Natural History Museum
Natural History Museum, Cromwell Road, London SW7 5BD, UK
Monday 29 November 2010
Overweight families have overweight cats, Detroit has a higher murder rate than the UK and a flock of goldfinches is called a charm. All these effects are evidently mainly environmental. They're caused by overfeeding, more gangs and guns, and the standard and focus of education, respectively. But Steve Jones, professor of genetics at University College London, UK, argued last week these factors are often overlooked because of our obsession with genetics.
In an annual lecture at London's Natural History Museum on 'nature -vs- nurture', Professor Jones emphasised the impact of genetics. Medical advances mean our lives are no longer most threatened by 'outside' causes, such as tuberculosis, cholera and influenza. Instead, he said, we're imperilled by conditions with strong genetic components, such as cancer, diabetes and heart disease.
Scientific knowledge of our genomes has promised much for our understanding of human behaviour and health. As Professor Jones put it: 'are people sick or well, geniuses or criminals, happy or sad, sane or bad because of their DNA?' But, he cautioned, geneticists have historically been overconfident about what the science can tell us. After On the Origin of Species was published, Francis Galton became convinced that abilities such as beauty, criminality and 'eminence' were biologically inherited and proposed eugenics to improve the population.
The importance attached to genes continues today: a Google search for 'scientists find the gene for' returned 36,000 hits. 'For', Professor Jones said, 'is the most dangerous word in genetics. The fact that something is inherited is absolutely not an indication that it is genetic'. Prince Harry inherited distinctive ears from his father, but Prince William will inherit the crown.
Obesity was Professor Jones' first example of where inheritance has been muddled. This condition runs in families. So is there a genetic component? One gene mutant is known to cause obesity: it curtails the production of leptin, a hormone which works in the brain to inhibit appetite. One in around 30,000 children are born with this condition and don't know when to stop eating. Studies have also shown identical twins who are told to eat as much as they can put on the same amount of weight, again showing genes are working in the brain.
Since then, more genes have been found that indicate if someone if likely to be overweight. But these have small, cumulative effects. 'It is genetic but it's a behavioural phenomenon, it's an appetite phenomenon', said Professor Jones. 'If someone is well educated and aware of the dangers of eating junk food then the gene would be much less of a problem than in a poorly-educated population'. Overweight parents may be more likely to have overweight children, but they're also more likely to have overweight cats. 'DNA runs in families, but so do frying pans', he added.
Criminality was his second example. Genes have been shown to influence the production of monoamine oxidase A, an enzyme which mediates response to fear. Around one third of the population have a low-activity form of the gene, meaning they have less of a reaction to scary events. 'So maybe your response to fear and to other emotions is to a degree controlled by that particular gene variant', said Professor Jones. 'The evidence isn't great but it's there, it's possible'.
However, another genetically-controlled substance also indicates criminality, he said - testosterone. Men murder around ten times as much as women and this peaks in the mid-twenties. The pattern is the same worldwide: in Detroit and the UK, for example. But in Detroit, the rate is 1,100 murders per million people; in the UK, 25 per million. Perhaps this is due to guns, drugs, gangs and poverty - all environmental.
And the charm? 'What is a flock of goldfinches called?' was a question in the 11+ test, the national exam meant to siphon off the most intelligent to a higher level of secondary education. But for this question to be a test of memory, children need to have learned the answer already. As Professor Jones put it, 'this was a 'gene for' test rather than a genetic one'.
Obesity, criminality and intelligence are complex issues, showing the tension between genes and environment. 'Nature -vs- nurture is in many ways a non-argument', concluded Professor Jones. 'It doesn't have the answers or the solutions - it just poses the problem in a different way'.