ancestor. The Ussher chronology of the 1650s had calculated creation at 4004 BC, but by the 1780s geologists assumed a much older world. Wernerians thought strata were deposits from shrinking seas, but James Hutton proposed a self-maintaining infinite cycle, anticipating uniformitarianism. Charles Darwin's grandfather Erasmus Darwin outlined a hypothesis of transmutation of species in the 1790s, and French naturalist Jean-Baptiste Lamarck published a more developed theory in 1809. Both envisaged that spontaneous generation produced simple forms of life that progressively developed greater complexity, adapting to the environment by inheriting changes in adults caused by use or disuse. This process was later called Lamarckism. Lamarck thought there was an inherent progressive tendency driving organisms continuously towards greater complexity, in parallel but separate lineages with no extinction. Geoffroy contended that embryonic development recapitulated transformations of organisms in past eras when the environment acted on embryos, and that animal structures were determined by a constant plan as demonstrated by homologies. Georges Cuvier strongly disputed such ideas, holding that unrelated, fixed species showed similarities that reflected a design for functional needs. His palæontological work in the 1790s had established the reality of extinction, which he explained by local catastrophes, followed by repopulation of the affected areas by other species. In Britain, William Paley's Natural Theology saw adaptation as evidence of beneficial "design" by the Creator acting through natural laws. All naturalists in the two English universities (Oxford and Cambridge) were Church of England clergymen, and science became a search for these laws. Geologists adapted catastrophism to show repeated worldwide annihilation and creation of new fixed species adapted to a changed environment, initially identifying the most recent catastrophe as the biblical flood. Some anatomists such as Robert Grant were influenced by Lamarck and Geoffroy, but most naturalists regarded their ideas of transmutation as a threat to divinely appointed social order. Inception of Darwin's theory Darwin went to Edinburgh University in 1825 to study medicine. In his second year he neglected his medical studies for natural history and spent four months assisting Robert Grant's research into marine invertebrates. Grant revealed his enthusiasm for the transmutation of species, but Darwin rejected it. Starting in 1827, at Cambridge University, Darwin learnt science as natural theology from botanist John Stevens Henslow, and read Paley, John Herschel and Alexander von Humboldt. Filled with zeal for science, he studied catastrophist geology with Adam Sedgwick. In December 1831, he joined the Beagle