Epigenetics as defined is "the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself."
Or according to wikipedia "epigenetics implies features that are "on top of" or "in addition to" the traditional genetic basis for inheritance."
Our Nature vs Nurture argument also includes the 'process' in which goes beyond the two dimensional framework of simple or complex architectures. Our sense of who we our, the actual thoughts of our perception is our perception and manifestation of who we can be and are. In so many words our thoughts become real through our intentions, actions and consequences.
If we believe that we are susceptible to die at 50 of a heart attack because it runs in the family, then by self-fulfilling prophecy it can come true, but if we believe that low stress life, eating right, exercising regularly will result in staffing off illness then that too can succeed. It is our Biology of Belief as author Bruce Lipton, PHD has stated. Our biology is affected by our emotional state(s) and by learning to control these states we can offset disease and even aging.