This extensively illustrated commentary on Darwin's Origin of Species offers a comprehensive, modern analysis of his revolutionary argument, situating his ideas within the evolutionary research and debates they inspired. Building on an unfinished manuscript by the pre-eminent evolutionary biologist Ernst Mayr, the book draws on more than 1,500 scholarly sources to expand on Darwin's revolutionary insights and to assess over 160 years of subsequent scientific progress. Each of Darwin's chapters is examined in detail, clarifying his reasoning while showing how his ideas have been refined, revised, or confirmed by later discoveries. In doing so, this new work highlights the enduring power and sweeping implications of Darwin's theoretical framework. More than 100 historical and scientific images illuminate Darwin's era and the central findings of evolutionary research, bringing the Origin vividly to life. The result is an authoritative analysis and synthesis of the most important scientific book ever written.