1. Weaver et al propose that among rats, maternal behavior towards newborn pups influences their cortisol response to stress via epigenetic mechanisms that change the expression of glucocorticoid receptor gene for the rest of the pup’s life. They argue that because epigenetic patterns are established at specific developmental periods, there is extreme time sensitivity to when the pup is exposed to particular maternal behaviors (licking and grooming, in this case), and maternal behavior before or after that sensitive period window is not as important. Do you think this mechanism is relevant in humans? If so, what behaviors are most analogous to “maternal licking and grooming”?
Yes, I believe that this mechanism is very relevant in humans. People often develop certain behaviors in childhood which spill into adulthood. One example of this is related to diet. If someone grows up in a household where they eat a lot of fast food their metabolism will change in childhood do to the poor diet. They will be obese as a child and then will continue to have issues related to the physiologic changes that occur in relation to poor diet and unhealthy eating. While I am not sure if there is specific receptor I could point to that would drive this epigenetic phenomenon, I believe that this is quite similar because it is a learned behavior which alters physiology and changes the way that the person’s body interacts with food in the future. Another potential similar behavior in development could be reading to children. When children are exposed to language at an early stage and their families read to them they will develop the language processing skills in their brain at a more advanced level. I believe that early exposure to reading and hearing will change the way that the brain processes things and this is similar to the epigenetic mechanism of the glucocorticoid receptor.
2. Gruenewald, in contrast, emphasize the cumulative effects of SES adversity on a multi-system allostatic load measure. Do you think that the Gruenewald findings are consistent, inconsistent, or unrelated to the Weaver findings? Explain.
I think that the Gruenewald findings are consistent with the Weaver findings. While the Weaver findings focus on the changes that occur from a positive behavior, such as licking and grooming, it is also possible that negative factors, such as SES adversity causes changes in biochemical receptors and in the way that our bodies cope with pressure in the future. I believe that while the Gruenewald finings apply to the entire life course, there is a high likelihood that SES adversity in childhood may be a bigger factor. In the data, they even compare the parameter estimates in childhood to the cumulative score and it was only “slightly higher” in the cumulative model. This indicates that while SES adversity on a multi-system allostatic load measure is important throughout life, much of the SES adversity comes in childhood. This is consistent with Weaver’s findings.
3. Hertzmann and Boyce argue that “it is not genes or environment, nor is it genes and environment, but rather it is gene-by-environment interactions that influence developmental trajectories.” To what extent do you think that GxE interactions can contribute to major disparities along racial/ethnic, socioeconomic, or geographic dimensions?
I agree with Hertzmann and Boyce that the Gene-by-environment interaction is likely more of an important factor in influencing developmental trajectories. Every person is born with a set of physiologic differences which will make them more or less likely to adapt or thrive in the environment they are in. Furthermore, the environment is fundamental at nurturing or hurting people as they are developing. I believe that the interaction between the environment and genes are fundamentally linked. Going back to my example about diet in childhood. If you want to study the outcome of childhood onset type 2 diabetes, there will be some children who are at increased risk of diabetes due to genetics and others who are not (assume for this example an undiagnosed gene mutation that increases susceptibility). If you fed both of them a high sugar unhealthy diet, the one at increased risk will be more likely to develop diabetes. If you fed both of them a healthy diet the one at increased risk will still be more likely to develop diabetes. However, the rate of diabetes would probably be highest in the unhealthy diet + gene mutation group due to the interplay between the genes and the environment. As some of the behavioral factors that are present in certain environments and these are often related to racial/ethnic, SES, or geographic dimensions, I think that the gene-by-environment interaction is the most important.