This book discusses the evidence for and against the heritability of acquired characters. Does the inheritance of acquired characteristics play a significant role in evolution? In this original and potentially controversial book the authors explore an often neglected aspect of Darwinian evolution - the nature and origin of hereditary variations. The theory of evolution proposed by Jean-Baptise Lamarck (1744-1829), that characteristics developed during life by use and disuse can be inherited by offspring, lost support among Western scientists because it lacked definite proof. Jablonka and Lamb do not act as advocates or apologists for Lamarck, but they do challenge the prevailing assumption that all heritable variation is the random result of variation in DNA base sequence. Looking afresh at the evidence for and against the heritability of environmentally induced changes, the authors ask some timely questions about the importance of non-mendelian inheritance. This important work will be of great interest to all biologists and historians of science.