Season 3, Episode 4: I Dream of Genomes
We first met Owen, a young man struggling with drug addiction, in Season 2. At David’s request, Bob tested Owen’s DNA and found that Owen had a strong genetic predisposition to addictive behaviour. Now, in Season 3, Owen is desperate to leave juvenile detention and believes that if he could be “cured” of his addictive tendencies, he just might be able to get out.
There but for the grace of genes …
Nature versus nurture – it’s an age-old debate. How much of what makes a particular person who they are is encoded in his or her DNA, and how much of it comes from life experiences, environmental exposure, and the choices a person makes?
In response to a query from the Edge World Question Centre in January 2006, American genomics researcher Dr. J. Craig Venter, one of the scientists who led the charge to sequence the human genome, said:
“…[W]hen it comes to humans we seem to like the notion that we are all created equal, or that each child is a "blank slate". As we obtain the sequences of more and more mammalian genomes including more human sequences… our new genomic tool sets [will] provide the means to allow us to begin to sort out the reality about nature or nurture…
It will inevitably be revealed that there are strong genetic components associated with most aspects of what we attribute to human existence including personality subtypes, language capabilities, mechanical abilities, intelligence, sexual activities and preferences, intuitive thinking, quality of memory, will power, temperament, athletic abilities, etc.”
As Dr. Venter implies, the biology of behaviour, or the extent to which genes can influence human behaviour, is currently the focus of some extremely exciting genomics research. But let’s not forget that while genes might influence how a person acts, they are not the whole story; social and environmental factors – including a person’s own choices – also play major roles.
As Dr. David S. Moore writes in his 2003 book, The Dependent Gene: The Fallacy of “Nature vs. Nurture”:
“…just as no single domino in a series can be called the cause–or even the most important cause–of an outcome, neither can a genetic factor alone be the cause–or even the most important cause–of the development of a trait. Instead, genetic and nongenetic factors determine traits’ appearances collaboratively.”
It’s important to remember that predisposition is not the same as predetermination. In other words, just because Ms. A’s genes make her more likely than Ms. B to develop Condition X, it doesn’t mean that Ms. A will develop that condition, or that Ms. B will not.
Similarly, just because Owen’s genes put him at risk of developing addictions, he can still choose to steer clear of drugs, alcohol, or gambling. But because of his genes, it might be a whole lot more difficult for him to “just say no” than for someone with a different set of genes.
Through studying the biology of behavior, we may figure out the biology behind why Owen and others like him struggle with addiction. That understanding could lead to new, effective drugs or other treatments that act on the underlying biology – like the chemicals in the brain or the receptors with which they interact – and help to counteract some of what is making life difficult for these particular addicts. Social programs, like rehabilitation and counseling, would likely still be necessary, but a treatment to counter the genetic influences might increase the likelihood of successful rehabilitation – at least for some.
But what about people who behave in certain ways in spite of having little or no genetic predisposition for doing so? Consider two addicts: If Addict A has a strong genetic predisposition to addiction, but Addict B does not, should society treat them any differently from one another?
Beyond addiction
Suppose Dr. Venter is right and we will soon understand much more than we do now about the genetic influences behind all kinds of behaviours, from addiction to violent tendencies. What should we do with all that information once we have it?
If science were to uncover genetic links to violent tendencies, for example, think of how that information might be used in court cases for violent offenders. The defense team might try to argue that the accused was not responsible for his or her violent acts, because “their genes made them do it.” The prosecution might counter by pointing out, as we have above, that genes might influence behaviour but do not necessarily cause specific actions. Or maybe the prosecution would seek to use such genetic information at sentencing and parole hearings, arguing that an offender with a genetic predisposition to violence might be at significant risk of re-offending if released from prison.
Are these sound arguments? It’s tough to say while the science is still in its infancy. Nonetheless, these examples serve to illustrate some of the ways that behavioural genetic information might be used, and perhaps misused.
What about other behaviours that one might categorize as more socially acceptable than addiction or violence, but that still are not seen as acceptable by everyone? Think back to Season 2, Episode 9, when the NorBAC team discovered some research that seemed to pinpoint a gene responsible for homosexuality in men. As our Facts Behind the Fiction pointed out, science has not yet identified the genes underlying sexual preference in people; but what if they were discovered? Might it lead some people to think of homosexuality as a “disease” that could – or even should – be treated? It’s an unpleasant scenario to consider, but is it an unrealistic one?
As scientists identify genes involved in behaviour, it may become possible to test or even screen for them. When should such testing be allowed? When, if ever, should it be encouraged? How might the availability of such tests affect people’s decisions around reproduction?
As science continues to uncover the genetic influences for human behaviour, scientists and the public alike need to consider how these discoveries should be communicated and what should be done with the new knowledge. Understanding the difference between predisposition and predetermination – between influence and control – is the key to protecting against inappropriate interpretation and use of behavioural genetic information.
More food for thought
Q: Once genetic linkages to behaviors are identified, how should we determine which if any to develop treatments for?
Q: What are your thoughts on nature vs. nurture? Do you agree with Dr. Venter that we will soon learn that there are “strong genetic components associated with most aspects of what we attribute to human existence ”? Why or why not?
Q: Who is responsible for ensuring that new scientific discoveries are communicated responsibly to the public? Scientists? The media? Who else?
Want to read and learn more?
To learn more about behavioral genetics, visit:
http://www.ornl.gov/sci/techresources/Human_Genome/elsi/behavior.shtml
To read Dr. Venter’s response to the Edge World Question Center’s 2006 question, “What is your dangerous idea?” from which his comments above were excerpted, visit:
http://www.edge.org/q2006/q06_12.html#venter
