Are Our Genes a Product of Us?
New studies show how exercise and a sense of well-being may affect epigenetics and gene regulation. So are we a product of our genes or are our genes a product of us?
A New York Times article, "How Exercise Changes Fat and Muscle Cells," discusses the correlation between exercise and changes in the epigenetic landscape in fat cells. Research indicates that exercise seems to affect methylation in a person's DNA. Methyl groups are signals that determine whether a gene is expressed or not.
The research was conducted by the Lund Diabetes Centre in Sweden. The study looked at the methylation landscape of fat cells of sedentary, but generally healthy, adult Swedish men before and after they were put on a regimen of one-hour of cardiovascular exercise twice-per-week for six months. The researchers found that the fat cells after the six-month period showed a different methylation pattern than before. Interestingly, "The genes showing the greatest change in methylation also tended to be those that had been previously identified as playing some role in fat storage and the risk for developing diabetes or obesity."
A second study, described by Emily Esfahani Smith in The Atlantic, discusses the correlation between hedonistic happiness, eudaimonic (meaningful) happiness, and gene expression. In other words, it looked at the difference between physical happiness and having a sense of meaning in life. The study indicates that hedonistic happiness has a genetic effect similar to that seen when people face chronic adversity. On the other hand, individuals who report having a sense of meaning and purpose in life show notably different genetic effects. In particular, experiencing a sense of hedonistic well-being, much like suffering chronic adversity, is associated with up-regulation of pro-inflammatory genes and down regulation of antibody-producing genes. With eudaimonic well-being, the opposite occurs: there is up-regulation of antibody producing genes and down-regulation of pro-inflammatory genes. These findings indicate that eudaimonic well-being may be more beneficial to health than its hedonic equivalent.
Neuroscientists often talk about the plasticity of the brain, but now the question might be the plasticity of our genes. Given these two studies, we need to address a couple of key questions:
- Is it true that behavior can change epigenetic factors (gene expression), or are scientists just jumping on the epigenetics bandwagon to explain otherwise inexplicable phenomena?
- If it is true that our behavior changes our genes, what does this mean for the current neo-Darwinian paradigm?
Turning from media reports to the actual journal articles, the PLoS One article on the correlation between exercise and methylation seems to reflect a more robust experimental basis than the PNAS article about well-being. The authors of the well-being paper specify some important limitations to their study, including testing a homogenous demographic. Furthermore, the study hinges on assessing hedonic versus eudaimonic well-being, both highly subjective conditions.
Moreover, studying human subjects always brings with it a host of tricky experimental variables. The methylation paper is intriguing because the researchers studied the same subjects before and after a six-month exercise regimen. Furthermore, this experiment noted that the key change in lifestyle for the test subjects was exercise, and the methyl patterns changed on the genes that are associated with fat storage, which strongly suggests some kind of real causative relationship.
If so, then what does this mean for the evolutionary mechanisms of natural selection coupled with mutations? It very well may be that an individual can change his or her genetic landscape through behavioral changes. This could mean selection for certain behaviors over others. However, it's complicated by the fact that an individual's behavior may change over a lifetime. Importantly, it is unclear if these genetic changes are passed to offspring and if the genetic changes are permanent.
On a philosophical level, these studies have implications for whether or not evolution is the only guiding force in how man came to be as he is today. If genes are the focus of the Darwinian mechanism, then what does it mean that man can change his genetics by changing his behavior? Perhaps Darwinian evolution explains less than previously thought, particularly in the context of human evolution -- as you know we've suspected all along.