Saturday, 5 October 2013

Scientists find the gene for…

Chimp holding a skull
Steve Jones begun his talk at the Henley Literature Festival by breaking the news that he was not the same Steve Jones who played guitar in the Sex Pistols. I was personally quite glad about this because it would have made writing this article on genetics somewhat difficult.

The Welsh geneticist and snail fan-iteration of Steve Jones has a new book out called The Serpent's Promise: The Bible Retold as Science. In the words of one of his reviews, it is a “re-cranking of the Darwinian barrel organ – accompanied by the monkey of New Atheism as it screeches petulantly at religion.” Sounds awesome, right?

His talk focused on the role of genetics in the nature versus nurture argument, using the bible as his starting point. Are we born already tainted by Adam and Eve’s transgressions in the Garden of Eden or, to put it in more scientific terms, is it worth trying to fight the genes we’re dealt at conception or are we all screwed before we even get started?

What does genetics tell us?

Are you sitting with a few others? If so, check out the two people closest to you. Statistically speaking, two out of the three of you are going to die as a result of your genes. Cheery thought, right? Although, in Shakespeare’s time, two of you would already be dead so that’s something to be thankful for. It was with this introduction that Jones begun his discussion of what genetics can—and what it can’t—inform us about who we are.

Clearly plenty of human attributes are linked to our genes. Thanks to my parents, I am at risk of developing high blood pressure and have my mother’s nose (in a jar on the mantelpiece, mwah ha ha). But it’s not a simple case of Genetics=Destiny, despite what certain scientists and members of the media would lead you to believe.

“Ignorance more frequently breeds confidence than does knowledge.”

Type ‘Scientists find the gene for’ into Google and more than 10,000 pages pop up. Among the hits is the slightly dubious premature ejaculation gene. Jones was quick to explain how this kind of reporting contributes to the public misunderstanding of genetics.

Overhyping the role of genetics is what was behind the UK’s disastrous Eleven Plus education policy in which they attempted to identify the ‘naturally talented’ kids worthy of a decent schooling. Take a class of kids and measure their IQ and there’ll be a natural variation in their scores. But we now know that, during childhood, genes can only explain 10% of this variation (interestingly, this goes up to 70% in the 65-70 age range). You see this when you look at twins adopted into different families—their environment plays a far bigger role in academic performance than genes do.

So the Eleven Plus didn’t really measure a child’s potential, all it did was deprive some kids of an education that could have drastically changed their life.

Extreme poverty drags everyone down regardless of genes

The part of the talk that stuck with me the most has to be how the contribution of genes to IQ differs dramatically depending on how rich you are. Among the top percentile for income, the contribution of genes to the population’s variation in IQ comes in at 0.7 (70% of the variation can be explained by genetic variance). Bottom percentile for income, and it drops to 0.1. For these people, their genes don’t make the damnedest bit of difference. Cue embarrassed shuffling from some members of the entirely middle- and upper-class audience.

It’s a similar situation when you consider the ‘gene for criminality’ found in half of the population. Yup, that’s the one responsible for testosterone production in the violent, dangerous creatures otherwise known as ‘men’. If you look at murder rates by age for men and women, those in possession of a Y chromosome commit around 10 times more murders than women. The peak age for criminality is between 20 and 30, gradually tailing off into ‘grumpy old men’ as Jones put it.

Compare the graphs for the UK and Detroit, and they look identical until you notice the scale of the Y axis. In the UK, the peak murder rate is 25 in 1 million. In Detroit, it’s 1000 in 1 million. Men still commit 10 times more murders than women but something about the environment has changed the scale of the problem. I’ve never been to Detroit and, after listening to Jones’ talk, I am not sure I want to.

Do our lizard brains impact on criminality?

Setting aside the limitations of brain scanning as a science, it can be used to demonstrate something really clever about how genetics can influence criminality. There’s this primitive little bit of the brain called the amygdala responsible for emotional responses and, if you surprise someone in an MRI scanner, you can make this region light up.

The degree to which the amygdala is activated depends on levels of a protein called monoamine oxidase A (MAO-A)—an enzyme involved in the transmission of nerve impulses. Those who are genetically programmed to produce low levels of MAO-A tend to respond more strongly to sudden shocks, giving them a worse temper than those who produce normal levels of MAO-A.

But MAO-A levels are not deterministic when it comes to aggression and criminality. There are plenty of people who make low levels of MAO-A (Steve Jones, for one) who don’t run around fighting and murdering. And there are people with normal levels who, thanks to their circumstances, end up taking a less than virtuous path in life. The interesting difference appears when we compare the effect of stress and trauma on antisocial behaviour in those who make low and high levels of MAO-A.

Normal levels of MAO-A + unstable childhood = 3 times higher rates of antisocial behaviour.
Low levels of MAO-A + unstable childhood = 20 times higher rates of antisocial behaviour.

It seems that, in this case, genetics can predispose someone towards violence but environment plays a huge role in deciding if a person will live up to their ill-fated inheritance. Should genes, therefore, be taken into account in the justice system? Should upbringing? Or are we all ultimately responsible for making the best of whatever cards we are dealt?

"We don’t need more geneticists, we need more theologians"

With genome sequencing becoming easier and cheaper, Jones believes that we will soon reach a point where it is possible to sequence the DNA of every child born in Britain. The problem is that this won’t tell us very much. No matter what genes we are born with, nurture still gets a look in. It’s why I get frustrated every time I see newspapers sloppily reporting scientific developments with headlines such as Are you a victim of the hunger gene? It misleads people into thinking that human behaviour can be explained in genetic terms when it is far, far more complicated in reality.

No comments:

Post a Comment