Developmental psychology emerged within the evolutionary, progressive though of the late 19th century. Concerned with processes by which new forms develop and new phenomena emerge, evolutionary thinking turned readily to the natural history of childhood. This series of seminal writings defines that movement. In 1877 the great biologist, Charles Darwin, and the philosopher, Hippolyte Taine, published short observations on the early development of their own children. When Wilhelm Preyer, a highly respected physiologist, followed with his own remarkable and much more extensive observations, the biographical study of childhood had begun in earnest.