Are We Hardwired?: The Role of Genes in Human Behavior

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 textbook 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 rather dry recounting of smaller species research. Unicellular paramecia, for example, exhibit avoidance behavior that can be disrupted via genetic mutation. Similarly, scientists have discovered mutations that can affect the learning abilities of certain fruitfly and roundworm species. Extrapolating from these findings, Clark and Grunstein meticulously detail how genetic alterations can disrupt neuron and neurotransmitter functioning in the human brain and thereby alter human behavior. Some of the behaviors 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 offer the general reader a well-organized, though occasionally tedious, overview that thoroughly addresses the major issues concerning this controversial subject. (Oct.)