Bittersweet Destiny combines discourse on the evolution of human behavior with a philosophical perspective. It explores evolutionary theory aimed at determining human behavior. Del Thiessen presents this material against the broad background of everyday life, allowing the reader to see the theory of evolution as it has shaped his or her own behavior. However, he points out that when evolutionary theory is aimed at human behavior, the critics object, and controversy results.

Thiessen argues that nothing in our lives makes sense unless we look at it through a biological lens. We can thereby understand our origin, our affiliation with all animals and plants, and our cultural destination. However, we can also discover a dark side to our destiny—our favoritism to those who share our own genes, our ability to deceive, and our capacity for abuse, rape, and murder. Good, bad, and indifferent, we serve the replication of our DNA. Critics extrapolate evolutionary theory to a wide range of animal species, and even human morphology and physiology, but when the same perspective is applied to human behavior there is strong dissent. What these critics fear, according to Thiessen, is that accepting evolutionary notions about human behavior strikes at the heart of free will, self-determination, and social equality.

Bittersweet Destiny describes the heroic efforts of naturalists Charles Darwin and Alfred Wallace to unlock the secrets of evolution. It continues with a vivid description of our fossil history and our chance beginnings. From there the story implicates disease processes in evolution, highlights our rational and irrational nature, focuses on those characteristics of brain evolution and language that make us distinctive, and illustrates our most basic survival and reproductive mechanisms. Thiessen warns the reader that things are as they are no matter what we might wish; we ignore facts and controversy at our own risk. This book will be significant to anthropologists, psychologists, biologists, and sociologists.