Updated: Jan 3, 2021
Evolution has instilled some essential mechanisms for survival in the human genome, for example, anxiety and fear. We essentially experience these phenomena to alert us to danger and keep us safe. Our ancestors may have experienced anxiety if they saw another person who did not look like them, as this other person may not have been from their tribe therefore posing a threat. We see similarities today with prejudice, racism, and social anxiety, however, the threats (generally) aren't actually there the way they were with our ancestors. Many people are afraid of heights, including when looking out of a window in a high building, why? Thousands of years ago if we were high up in the tree canopy without footwear or ropes, the danger of falling and dying is very real. The danger is simply not there in the case of looking out a window, yet some still experience the fear. This may be rooted in our ancestors' anxiety around heights. Why do so many of us overeat? If we think of this evolutionarily, it makes perfect sense. When we were scouring the desert or forest for food, food was scarce, and we did not know when we may eat again, nor did we have the ability to carry and preserve our food the way we do today. In present-day we have an overabundance of food and this evolutionary mechanism is no longer useful, nor are several other evolutionary mechanisms. When we respond to the old mechanisms that are no longer helpful, we reinforce (via learning) their original intent and validate our fears as legitimate, which in turn affects our genetic expression.
As we know, natural selection has allowed those with the most adaptive traits to survive. If our ancestors were afraid of heights while in the trees perhaps they were at less risk of falling because the anxiety is a sign to be cautious. If they overate they were at a greater risk of surviving because they had adequate nourishment. If they were defensive against other tribes, they were less likely to be killed. The adaptations resulted in variances within genetic expressions which were passed along trans-generationally. This is a process that continues to happen and is a topic within the field of epigenetics. This is why there is transgenerational trauma as well as stress resiliency amongst holocaust survivors and their decedents. When we allow fear and anxiety to rule our lives by partaking in unnecessary neutralizing or compulsive behaviors, we are affecting the way our genes are expressed and continue to pass these traits down the family line. Genetics is one of the reasons why we say "X, Y, or Z runs in the family." The really cool thing is we can begin to break that cycle. This is really mind-blowing, earth-shattering stuff! We can possibly begin to break the maladaptive cycles by changing our behavior, which in turn changes how our genes are expressed, which changes how traits are expressed in our decedents. (The field of genetics is very complex and there is much, much more to it than I described. If you're interested in the subject I suggest looking into transgenerational trauma).
To put this into context; let's say anxiety runs in my family. My mom, grandma, and great-grandma all had anxiety revolving around different themes. They never sought treatment and would give in to what the anxiety said: "Worry about this, check that, ask about this, don't do that, be careful about this." Now let us say I come along riddled with anxiety. If I do things differently, such as exposure response prevention, change my cognitive behavior, practice mindfulness and so forth, I begin to alter my gene expression and make it less likely for my children and grandchildren to inherit the same trails my mom, grandma, and I did. The same goes for addiction. Humanity as a whole needs to look at how they have and continue to respond to stimuli in a maladaptive way and be curious about doing something different; not just for ourselves, but for generations to come.