How Our Environment Changes Who We Are
I recently came across a YouTube video titled “5 ways to build an Alzheimer’s resistant brain”. This was interesting to me, as Alzheimer’s is generally considered a heavily hereditary disease, meaning if someone in your family had it, it is likely that you will too - it is a trait that is passed down through family. However, in the video, Lisa Genova, a renowned author and neuroscientist explained that “Only 2% of Alzheimer’s is 100% genetic. The rest is up to your daily habits”. Even though Alzheimer’s is a hereditary disease, not everyone expresses the gene.
Epigenetics is the study of how an individual's environment changes their genetics and how their genes are expressed. It is a way of understanding human evolution and variation on an individual and societal level.
For decades, the famous debate about nature versus nurture has been a hot topic in the genetic world. Now we know for a fact, it is almost always both. Everyone is born with a set of genes inherited from both parents, half from mom and half from dad; this is the nature side of the debate. We all have predisposition to certain traits and diseases because of what we inherited from our families. So why does one twin get a disease and another is perfectly fine? Why do we never know for sure if a trait will be expressed in someone? The answer lies in epigenetics, the nurture side of the debate. Believe it or not, our environment, habits, and lifestyle play a major role in which genes will actually be expressed.
While most of us are born with 46 chromosomes and a set genetic makeup, every trait is not expressed. This is caused by many biological processes that contribute to epigenetics, including a process called DNA methylation. DNA methylation occurs when a methyl group is attached to a specific point on a DNA strand which prevents transcription, an important step in the process of turning DNA into a functional protein that accomplishes a task in our bodies. Demethylation is a process where these methyl groups are removed, allowing that gene to be expressed. In short, if there is methylation on a gene, it will not be expressed even though that gene was inherited.
Recent research tells us that environmental factors can actually affect methylation patterns, and therefore affect which genes and traits are expressed. Some of these factors may include “migration, nutritional stress, psychosocial stress, and social inequalities, etc.”, according to a 2015 paper. In fact, epigenetics can cross generations and affect societies and cultures.
In the winter of 1944-1945, there was extreme famine in the Netherlands as a result of a food blockade during World War II. Interestingly, generations later it was seen that their descendants have an average weight of a few extra pounds. This adaptation likely helped store fat and nutrients for longer amounts of time due to famine. The trait is beginning to fade out as it is no longer necessary. This is an important example of epigenetics in the real world; those who lived during the famine had altered gene expression that allowed them to survive, which was passed down to their children, but not in their bloodline forever.
Epigenetics can help us or hurt us. Lifestyle choices and our environment play a major role in what genes will be expressed. Therefore, if one’s environment is not conducive to a healthy lifestyle, they will likely face health issues that may not have been a problem with a better lifestyle. On the other hand, our bodies are wired to survive by whatever means possible, sometimes changing what genes are expressed for this goal, like in the case of the Dutch famine. Anthropologists are now able to track lifestyle and culture around the world with epigenetics, an emerging field of importance for both the life sciences and the social sciences.