This work is intended to portray the interrelationship of heredity‎,‎ individual development‎,‎ and the evolution of species in a way that can be understood by nonspecialists‎.‎ In striving to offer a straightforward historical exposition of the complex topic of nature and nurture‎,‎ the author tells the story through a central cast of characters beginning with Lamarck in 1809 and ending with a synthesis of his own that depicts how extragenetic behavioral changes in individual development could be the first stages in the pathway leading to evolutionary change‎.‎ On the way to that goal‎,‎ he describes relevant conceptual aspects of genetics‎,‎ embryological development‎,‎ and evolutionary biology in a nontechnical and accurate way for students and colleagues in the behavioral and social sciences‎.‎ The book presents a highly selected review as a prelude to the description of a developmental theory of the phenotype in which behavioral change leads eventually to evolutionary change‎.‎ This book grew out of an invited interdisciplinary course of lectures for advanced undergraduate and graduate students at the University of Colorado‎,‎ Boulder‎.‎ Presenting the various ways about thinking about heredity‎,‎ individual development‎,‎ and evolution‎,‎ the author had three goals in mind‎:‎ *to establish the relevance of individual development to the evolution of species‎;‎ *to describe the most appropriate way to think about or conceptualize heredity in relation to individual development‎;‎ *to show that this somewhat unorthodox manner of conceptualizing heredity and individual development gives rise to a new way to think about the behavioral pathway leading to evolution‎.‎ In conclusion‎,‎ the present work will provide a contribution toward the possible dissolution of the nature‎-nurture dichotomy‎,‎ as well as a contribution to evolutionary theory‎.‎