Johannes Gerardus Keulemans: A Life in Feather and Brush Early Life and Education Born: June 8, 1842, Rotterdam, Netherlands. From a young age, Keulemans demonstrated an interest in the natural world, collecting animal specimens. This early passion led him to connect with Hermann Schlegel, director of the Natural History Museum in Leiden, who became a crucial mentor. Schlegel encouraged Keulemans’s artistic talent and sent h…