ABSTRACT
This chapter introduces the value of twin studies and the problems inherent in them. This will lead, in turn, to adoption studies, which more clearly separate genetics and the environment. Numerous researchers from many countries have amassed convincing data that demonstrate the relationship between genotype and behavior. Some of these studies have limitations, which will be discussed, but overall the evidence for a relationship seems overwhelming. These genetic studies also provide some of the most important data about the role of the environment in criminogenic behavior. It is clear from these studies that biological influences on behavior such as hormonal imbalances can be therapeutically altered or changed. Most of us have heard of hormone replacement therapy for menopause. Often, it is thought that if a behavioral problem has a genetic basis, then there can be no cure and DNA becomes destiny. This chapter begins to explore the reasons this is not so.
