A Critique of the Theory of Evolution

Thomas Hunt Morgan separates evidence that living things vary over time from explanations of how those changes occur. Based on four lectures delivered at Princeton in 1916, this scientific study reassesses older arguments for evolution through newer work on inheritance. Comparative anatomy, embryology and fossils sit alongside discussions of Mendel's discoveries, mutation and natural selection. Morgan's opening insists that tracing a sequence of changes does not, by itself, explain their causes.

The discussion becomes concrete through Drosophila, with inherited differences in wings, eyes, body color and bristles. Groups of traits that tend to pass together are compared with the fly's four pairs of chromosomes, connecting visible variation to structures inside the cell. Readers interested in the history of biology can follow how Morgan builds an argument from experimental observations. The lecture format brings broad evolutionary questions into contact with the detailed work of studying heredity.