For several years, the origin of inexplicable fears such as arachnophobia or acrophobia has remained an enigma. How, why, and by what means such fears develop was a prevalently unanswered question, until a study involving mice opened a complex, intricate gateway into the world of epigenetics and provided some insight into this phenomenon. In fact, recent research and experimentation affirm the possibility that personal fears, experiences, and memories can be successively passed down from ancestors to their progeny.
This discovery was first made recently at Emory University, where scientists, by methodically subjecting them to pain, induced mice to associate fear with a particular odor. Subsequently, they found that the next two generations of mice were behaviorally sensitive to that very smell, but not to other similar ones. Even offspring that were fathered through in vitro fertilization related panic to the odor .
There are a plethora of such devices that potentially justify how memories can be transferred with such efficiency. For instance, blood-borne odorants might trigger receptors on sperm, which in turn instigate specific reactions to certain circumstances of danger .
Offspring not only mirror the exact psychological reactions of their parents when facing similar dangers, but also become sharply aware of the environments that characterize such threats. Research claims to possess evidence for the concept of animals obtaining a memory of their ancestors’ traumas, and responding as if they had lived the events themselves. How far into their ancestry these memories originate is still unknown. According to another experiment conducted at Emory University, indicators of anxiety were far more common in teenagers whose mothers were physically abused in their youth than those whose mothers had never experienced such maltreatment. Furthermore, the children of abused mothers appeared to have higher levels of sympathy towards other youth, unlike their counterparts .
Another biological medium that could unravel the aforementioned mystery is noncoding RNA. A specific noncoding RNA, piRNA, performs its functions primarily in the gametes of eggs and sperm. More significantly, piRNA not only heavily influences DNA methylation, or the modification of a strand of DNA after replication by the addition of a cytosine molecule, in order to silence genes, but they can regulate expression of genes encoding for proteins. Thus, its features could collectively delineate exactly how intangible experiences are passed down physically through parental DNA strands .
Additionally, a parent’s trauma can contribute to the gene activation of their children. Particularly, since the struggles of a parent can diminish their interaction with children, the latter suffer a subsequent change in their epigenome, the chemical markers that determine gene functionality. This facet of fear transmission is delineated through an experiment of the aforementioned university. In the study, children of women who suffered post-traumatic stress disorder due to the September 11, 2001 terrorist attacks had far lower levels of cortisol (much like their parent) than other children their age .
Ultimately, the reasons behind why exactly a parent would innately transfer only certain memories to their children could lie in their desire to protect and prepare children if they were to encounter a similar dangerous environment in their own lives . These fears, memories, experiences, and perceptions of the parents even impact the physical development of their children. Therefore, their offspring develop neurons and altered structuring in other parts of their body that correspond to the sensation of dread or anxiety that their parents experienced. For example, if a parent associates a smell with an emotion of fear, their kids have an olfactory sense pinpointing or targeting that odor. In other words, the areas that detect that smell undergo structural changes .
This, in turn, may be the root cause of inexplicable, irrational, yet inherent phobias, from a basic fear of heights to that of spiders. These phobias may in fact be defense mechanisms that were used by ancestral individuals who had a frightening experience with insects or tall building. Thus, before even conceiving offspring, parents are able to influence the nervous system of their progeny. However, not just phobias are passed down. This trend holds true for food preferences, obesity and even psychological behavior .
Ultimately, trans-generational inheritance of trauma introduces a large leap in the field of epigenetic biology and provides societal perspective on the importance of ancestral impact on the widespread propensities of their offspring.
References Kerry J Ressler; Brian G Dias. “Parental olfactory experience influences behavior and neural structure in subsequent generations.” Nature Neuroscience: 89-96.  Tabitha M. Powledge. Genetic Literacy Project, “Can we inherit fear of a smell? The latest on transgenerational epigenetics”  Tanja Jovanovic, Ami Smith, Asante Kamkwalala, James Poole, Tara Samples, Seth D Norrholm, Kerry J Ressler, and Bekh Bradley. “Physiological markers of anxiety are increased in children of abused mothers.” Journal of Child Psychology and Psychiatry, and Allied Disciplines.  Rachel Yehuda, Stephanie Mulherin Engel, Sarah R. Grand, Jonathan Seckl, Sue M. Marcus, and Gertrud S. Berkowitz. “Transgenerational Effects of Posttraumatic Stress Disorder in Babies of Mothers Exposed to the World Trade Center Attacks during Pregnancy.” The Journal Of Clinical Endocrinology & Metabolism.  Hughes, Virginia. “Mice Inherit the Fears of their Fathers.” National Geographic.  The Mind Unleashed, “Scientists have found that memories may be passed down through generations in our DNA.”
Image Credit: Retrieved September 13, 2014 from: (Creative Commons): Mehmet Pinarci, 2014. “DNA Strand.” Flickr.