"Not all DNA gets used. The environment results in certain pieces getting turned on or off. We knew this happened to children, but we thought it was fairly limited and wouldn't have large effects except in extreme situations, such as abuse. It turns out that it effects everyone. Small variations during childhood can have vast effects on an individual's behavior. It also doesn't stop during development, but continues being a major factor throughout the individuals life. So, if you had different parents as a child or grew up in a different culture, you would be a very different person."