This text investigates the fundamental biological mechanisms through which organisms develop traits to survive and reproduce within their specific environments. Sir Gavin De Beer, a distinguished evolutionary biologist and former director of the British Museum (Natural History), utilizes his extensive expertise in embryology and comparative anatomy to explain the process of adaptation. He presents a framework that connects genetic variation, natural selection, and environmental pressures to demonstrate how species evolve over time. The work serves as a concise synthesis of mid-20th-century evolutionary theory.

Experts recognize this volume as a foundational entry in the Biology Readers series, valued for its clarity and historical context. Readers frequently note the accessible nature of the prose, which distills complex evolutionary concepts into a format suitable for students and interested laypeople.