It's an article I had a hard time picking a snippet from, so I recommend just reading the source. But I grabbed one anyway as a taster.

"The changes in DNA structure are random events that acquire functional significance in the context of Darwin's "natural selection" process. In contrast, the epigenetic reactions to specific environments are designed to enable that organism to cope with that context. When these traits are passed to the next generation, it is as if the newborn arrives prepared for that specific environment. Problems arise when the epigenetic processes give rise to traits that are not adaptive for the offspring, such as heightened stress reactivity, or when the environment has changed."

http://www.sciencedaily.com/releases/2013/02/130214075539.htm