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Key points
- Who we become is not derived solely by our genes.
- The environment alters gene activity through a process called epigenetics.
- There are many possible versions of “you” in your genome.
The mystery of differences in identical twins
Scientists have long been puzzled by a phenomenon among identical twins called discordance. Despite having the same DNA, aging twins can become discordant for certain traits. One twin can be taller than the other. One twin can become obese while the other stays lean. Identical twins can also be discordant for depression. Discordant twins suggest that our physical and psychological makeup does not arise from genes alone. A landmark 2005 study explained this mystery: Epigenetics.
There are at least two ways a change in DNA can affect a person’s appearance or behavior. One involves mutation—when an alteration in the gene sequence modifies the protein made by that gene. A single mutation in one gene can cause diseases like cancer or sickle-cell anemia. Epigenetics is a more recently discovered way that genes can be altered. Instead of a gene mutation, the gene’s activity is increased or decreased. For example, molecules called methyl groups can be attached to a gene, which diminish its activity. If a gene becomes heavily methylated, it can be completely shut down.
The 2005 study showed that young identical twins, in addition to having the same genes, have highly similar DNA methylation patterns. In contrast, the DNA methylation patterns in older twins diverge. The twins still have the same genes, but they are not activated in the same way. It’s like two identical houses but with dimmer switches set to different levels in every room. The variation in their gene activities can lead to physical and psychological differences sometimes observed in identical twins.
How do people become who they are?
It is now understood that virtually anything in our environment can alter gene activity: diet, exercise, drug use, pollution, and more. Perhaps more surprisingly, experiences can also alter gene activity through epigenetics. Children who suffer trauma have epigenetic changes in genes regulating stress responses, which may explain why many grow up to have health and behavioral problems. Emerging studies have also implicated epigenetics in several types of mood disorders.
The brain—the seat of the self—appears to be restructured at an epigenetic level when new things are learned or committed to memory. Mindfulness and meditation can also alter the epigenetic landscape. While this field, dubbed neuroepigenetics, is in its infancy, preliminary results suggest that gene activity in our brain is modulated, at least in part, through epigenetic factors acted upon by our environment and experiences.
There has been ongoing debate as to whether nature (our genes) or nurture (our environment) is more important in making people who they are. The science of epigenetics illustrates that the nature-nurture debate is a false dichotomy; rather, they are two sides of the same coin. A useful analogy is that our genes are like piano keys, but the environment plays the song.
These findings have profound philosophical implications that mirror the Buddhist idea that the self is an illusion. Instead of thinking of the self as a static entity, epigenetics argues that it is a dynamic work in progress influenced by outside forces. It is fascinating to think that the self you currently experience is just one of many versions of you that could have been coaxed out of your DNA by different environments. In other words, if you were raised in a different time or place, you are not likely to become the same person.
Is our fate written in our DNA?
There’s no escaping which genes we are born with, but what truly governs destiny is which genes are activated and by how much—variables that are influenced by the environment through epigenetics. A familiar example illustrating the intimate relationship between genes and environment is height. A person could be born with a genetic potential to be six feet tall, but that height is less likely to be realized if the individual suffers malnutrition.
Returning to the piano metaphor, these findings indicate that while we cannot change our genes, we may be able to tweak the song by affecting epigenetics. In 2016, scientists showed that it was possible to reprogram an ant’s behavior—turning soldiers into foragers—by administering a drug that altered epigenetic activity in the brain. In humans, drugs with antimanic and antidepressive activities can modulate epigenetic processes, which could underlie their therapeutic effect.
Aside from epigenetic drugs, another way to leverage the power of epigenetics for change is by reengineering one’s environment. Healthy lifestyle choices engage epigenetic factors to regulate gene activities conducive to well-being. Proper diet, exercise, sleep, stress reduction, and avoidance of toxicants like smoking and alcohol produce positive changes in mood, outlook, and personality. The health benefits enjoyed by those who practice compassion and have strong social ties are likely brought about through epigenetic changes in gene activity regulating stress responses and immunity. Most surprisingly, epigenetics may be at the heart of mind-body therapies, suggesting that our own thoughts can become an environmental force that may influence gene activity.
The remarkable discoveries in epigenetics suggest that there are many ways people can change by restructuring their environment.
