Above: Image © istockphoto.com/J614
Have you ever wondered why you do certain things a particular way? Naturally, your family has a big influence on your behaviour. However, it may not just be a result of watching and listening to your parents as you grow up. A 2014 study published in Nature Neuroscience suggests that your family’s influence may go much deeper than that. The same way your parents’ and grandparents’ DNA influences traits like your eye colour, you may actually inherit behaviours.
Fast fact: Classical conditioning was discovered by Ivan Pavlov, who observed that dogs learned to associate the sound of a bell with the arrival of food. When the dogs heard the bell ring, they began to drool.The scientists behind the study found that a learned behaviour could be shared across three generations not through social interaction, but instead through a type of genetic inheritance. The researchers began by training mice to be afraid of a specific odour using a method called classical conditioning. After receiving a mild shock in a box that smelled like almonds, the mice began to show fear whenever they smelled that odour.
These trained mice were then bred, and the new generation of mice were raised separately from their parents. Amazingly, this new generation (the “children”) also showed fear when they smelled almonds, even though they had never been shocked like their parents. Even more amazingly, the next generation of offspring (the “grandchildren”) also showed the same fear.
Since the parent mice weren’t able to teach their children and grandchildren to fear the odour, how is it possible that this behaviour recurred across generations? To find out, the researchers compared the DNA of the parent mice to the DNA of their children and grandchildren. They found that the parent mice had changes in a gene responsible for detecting the smell of almonds in the nose. Incredibly, they found genetic changes in the children and grandchildren as well! This suggests that the fear learned by the parents may have been passed on to the children and grandchildren through inherited changes in DNA.
Although this study is controversial, these results are consistent with other finding made in a field called behavioural epigenetics. Epigenetics is the study of how different molecules can “turn on” or “turn off” genes within your DNA without changing the sequence of the DNA itself. These molecules affect your DNA as a normal part of your development, and influence things like your growth and metabolism. Epigenetic changes can also occur in response to outside influences, like exposure to chemicals in your environment.
Fast fact: The “nature vs. nurture debate” refers arguments about whether your genes or your experiences are more important in determining what kind of person you are.In behavioural epigenetics, scientists are investigating the possibility that what you learn during your lifetime may also cause these molecules to affect your DNA, and whether these changes could be passed on genetically to future generations. For example, some behavioural epigenetics research using rats suggests that better attention and care from mothers may not only make you a calmer child. It could also cause changes in your DNA that make you less sensitive to stress as an adult.
Research in behavioural epigenetics may help explain why different people can react so differently to the same environment. Why do some people who are raised in poverty manage to succeed, yet others struggle? Why do some people who have access to good food become overweight, yet others stay healthy?
Behavioural epigenetics also puts a fascinating spin on the nature vs. nurture debate, because it raises new questions about why we behave the way that we do. Are you affected only by what you learn during your own lifetime, or do your parents’ and grandparents’ experiences also influence how you do certain things? And if your parents’ and grandparents’ past experiences do, in fact, affect your genes in some way, can these changes be undone during your lifetime?
So the next time you get a rush from tackling a super-steep ski slope that makes your friend feels faint, you may want to thank your daredevil great-grandmother for your fearlessness.
Grandma's Experiences Leave a Mark on Your Genes (Dan Hurley, Discover Magazine) Nature vs nurture: outcome depends on where you live (Nick Collins, The Telegraph)
Scholarly publications and textbooks
Dias BG, Ressler KJ. 2014. Parental olfactory experience influences behavior and neural structure in subsequent generations. Nature Neuroscience. 17:89–96. Gray, P. Psychology. 1999. Worth Publishers, New York, NY.Jones, PA, Baylin, SB. 2002. The fundamental role of epigenetic events in cancer. Nature Reviews Genetics. 3:415–428 Simmons, D. 2008. Epigenetic influences and disease. Nature Education. 1:6. http://www.nature.com/scitable/topicpage/epigenetic-influences-and-disease-895 Szyf, M. 2014. Lamarck revisited: epigenetic inheritance of ancestral odor fear conditioning. Nature Neuroscience. 17:2–4. Szyf M, Weaver IC, et al. 2005. Maternal programming of steroid receptor expression and phenotype through DNA methylation in the rat. Frontiers in Neuroendocrinology. 26:139-62.