In this second edition of the classic work Foundations of Mathematical Genetics a definitive account is given of the basic models of population genetics, together with the historical origins of developments since 1908. Existing texts in mathematical population genetics have revealed the need for a careful study of the foundations of the field which have tended to be neglected in the past. This book satisfies that need, treating the simple deterministic models for random-mating diploid populations in depth, though without sacrificing clarity of expression. In the new edition, coverage has been extended with the provision of an extra chapter on the Fundamental Theorem of Natural Selection. This book is written for those interested in the mathematical aspects of genetics, ecology and biology. Both students of mathematical genetics and historians of the subject will find it a definitive statement of the origins of modern mathematical population genetics.