Share thisWhat It Is and Why It Matters to Behaviour Research
Until recently many people thought that irrespective of the environment, genes delivered a fixed set of characteristics— such as personality, height, talents, or illnesses. It turns out this was only part of the story. Genes seem to set the limits of an organism’s potential rather than a predetermined set of characteristics.
Furthermore, genes are active only in the presence of biochemical triggers, like the frog who needed a kiss to become a prince. We also know that the expression of some genes is constantly changing in response to the internal and external environment, and absence of the right signal could leave a gene forever dormant. In other words, although genes set boundaries around the potential of the system, the environment determines the extent to which potential is reached.
This less linear, more interactive standpoint, which we call the psychobiology of gene expression, accepts that the influence of genetics and environment are both strong and begs us to revisit old questions with new lenses. Rather than asking questions such as “Is behaviour X a result of nature or nurture?” scientists now ask questions such as “How do genes and the environment interact to influence behaviour X?” and “By what mechanisms do genes and the environment interact to change the nervous system’s function?”.
Today’s explanation goes like this.
Genes code for proteins, and only proteins. If something is not a protein, there is no gene for it. Traits like maternal behaviour, intelligence, and personality are not proteins. There are no genes for these. When scientists speak of a gene for behaviour, let’s say intelligence, what they really mean is that there are genes for proteins that alter the function of the brain in such a way that they affect what we measure as intelligence. Furthermore, differences among individuals are not always in the nucleic acid sequence of the gene. The sequence determines the structure (and therefore the function) of the protein. Sometimes the difference is in the amount of protein present. That is, some individuals make more of a protein than other individuals. This, plus variations in experience, can affect the amount of neurotransmitter, the receptor, and others among the brain’s structural and functional elements which influence emotion, perception, and behaviour—in this case, intelligence. The level of gene expression is not directly related to the sequence of the gene, but rather to whether the cell’s biochemical machinery is active at that gene.
As an intuitive example, consider height. The average height in many societies has increased over the past few decades. Grandchildren tend to be taller than their grandparents. Such a change has occurred far too rapidly to be due to changes in the genetic composition of the population. A likely explanation is that the genes that regulate and build the body are sensitive to the nutritional status of the person. More food keeps these genes active longer, and the person becomes taller. So it is far more likely that environmental conditions— in this case the availability of food—are responsible for the overall height change.