Have you ever known identical twins and wondered why they don’t look exactly the same? Why if two individuals have exactly the same genes don’t they look the same? Similarly, if two children are brought up together and at the same time, why don’t they act the same?
This is the foundation of the nature – nurture debate. This debate looks at the role the environment (or personal experience) and/or genes have on determining individual behaviour. Scientists used to be happy to say that individual behaviour was “a bit of both” (i.e. a mixture of nature and nurture), but with advancing technology this is no longer the case. Scientists are now developing this area and determining which specific behaviours are manipulated the most by either the environment or genes.
It is not just Biology in which this area is relevant. The debate has had an influence in anti-social behaviour, and the theory that a child brought up in an abusive environment will itself be abusive later in life. In more extreme cases, people on trial for rape have even claimed that they have a “rape gene” and despite their environmental upbringing they were “programmed” to commit this crime.
So how do you test if a particular behaviour is the result of the environment or genes? As mentioned above identical twins are often used in this area. Twins are genetically identical, so output studies can be used to measure environmental effects on behaviour. This includes things like reaction times and academic ability. These are both easy to measure and are completely non-invasive.
A popular topic at the moment is the field of epigenetics. This is the study of how environmental information (and experiences) can be transmitted from one generation to the next. Today an article from science daily discusses the importance of epigenetics in our understanding of brain plasticity, the cognitive benefits of motherhood, and how a parent’s exposure to drugs, alcohol and stress can alter the brain development and behaviour of their offspring.
Ultimately the nature nurture debate will still go on. I would imagine the public find it a little unsettling to think the way we behave is already “decided” before we are born. Likewise, if a child has had a particularly bad upbringing, it would be unsettling to think their environment will decide the way they will behave. The link between genes, the environment and behaviour is a complex relationship. Common consensus is that, while the presence or lack of a gene might make us more likely to do something, we still choose how we behave, and have control over our lives. How this will be manipulated in the courts is another matter. I can just imagine a defendant arguing his or her genes “made them do it”.