EVOLUTION AND ADDICTION Proximate explanations

An evolutionary approach to behavior is wonderful because is poses fundamentally new questions. It is also difficult, however, precisely because these questions are new and therefore hard to formulate clearly and even harder to answer. The papers in this special issue (Dudley 2002; Gerald & Higley 2002; Hill & Chow 2002; Lende & Smith 2002; Newlin 2002; Panksepp et al. 2002; Sullivan & Hagen 2002) tackle the problem of substance abuse from an evolutionary perspective. They range from deductions about risk-taking based on life history theory to adaptationist hypotheses about the possibility that drug use has been useful in our past, and therefore selected for. Those who are unfamiliar with such questions will appreciate a sketch of the larger framework in which evolutionary and proximate explanations are both needed to fully understand any biological trait. Most substance abuse research has addressed the problem of why some people abuse drugs and others do not. The core challenge has been to explain individual differences. This focus arises from practical concerns—if we know the factors that predict who will abuse substances we should be able to change them and thus assist prevention and treatment. Much of the debate in the field has been between those who emphasize the importance of genetic differences and those who call attention to the roles of life experiences and psychological factors. Much of the progress has come from studies of the brain mechanisms—how they are changed by drugs and how they lead to drug craving and using. All of these questions and answers are fundamentally the same, however, in that they examine how things work. Together, they constitute what evolutionary biologists call a proximate explanation for substance abuse.