To allay the growing concern surrounding the implications of behavioral genetics research, UCLA professors Clark (A Means to an End) and Grunstein present an illuminating survey attempting to clarify the extent to which human behavior is influenced by genes, the environment and free will. In efficient style, the authors propose that 50% of human behavior can be accounted for by DNA and seek to defend this hypothesis through an accessible examination of studies of twins and a recounting of smaller species research. Unicellular paramecia, for example, exhibit avoidance behavior that can be disrupted by genetic mutation. Similarly, scientists have discovered mutations that can affect the learning ability of certain fly and roundworm species. Extrapolating from these findings, Clark and Grunstein meticulously detail how genetic alterations can disrupt neuron and neurotransmitter function in the human brain, and thereby alter behavior. Some of the behavior that genes may mediate are aggression, substance abuse, mental functioning and sexual preference. Clark and Grunstein show that identical twins often possess similar mental capacities and even a similar likelihood of becoming substance abusers. For males, preliminary studies indicate that aggression and sexual preference may be heritable through the Y chromosome. Clark and Grunstein are quick to note, however, that the way a gene is actually expressed depends on environment and experience, which can reroute neuronal connections, resulting in an ever-evolving, complex matrix. Genetic determinism has recently received plenty of attention from scientists and ethicists, and Clark and Grunstein offet the general reader a well-organized, though occasionally tedious, overview that thoroughly addresses the major issues concerning this controversial subject.

In contrast, William Clark and Michael Grunstein, an immunologist and a molecular biologist, argue the case for genes in "Are We Hardwired? The Role of Genes in Human Behavior." They summarize evidence collected mostly over the past decade using studies of human twins and new techniques in molecular biology. They argue that genes are especially important in explaining differences among individuals (why is it that some of us can eat poorly and not get fat?). On average, they estimate, about 50 percent of variation among individuals is related to genetic differences. Molecular biologists Clark and Grunstein see…hope in the promise of molecular medicine, which may eventually provide the key to preventing alcoholism, drug abuse and obesity. The failure to find the right genes so far "simply makes the challenge more interesting."

In this challenging and astute entry in the ongoing nature/nurture debate, William R. Clark and Michael Grunstein draw insights from both sides of the argument and present a provocative interpretation of this complex issue. Are We Hardwired delves into modern genetics and behavioral science, noting that complexes of genes, often across chromosomes, drive most of our heredity-based actions. The authors examine the genetic basis of behavioral traits such as aggression, sexuality, mental function, and alcoholism. They reject the idea that genes and environment are in opposition, arguing that heredity shapes how we interpret our surroundings, which in turn changes the very structure of our brain.