Rosemary Hill at The Guardian:
The first readers of Middlemarch in 1872 therefore looked back at Casaubon across a vast intellectual gulf. Understanding of humankind and its place in time had been transformed in a generation. It is perhaps surprising that Kidd makes no direct reference to Lyell or Darwin, but in fairness they made at first no fundamental difference. The mythography of the mid-Victorians continued to absorb the discoveries of archaeologists in Nineveh and Egypt, of explorers and scientists within an overarching theory of “development”. In theology, in the architecture of the gothic revival, as well as mythography and geology, creation could be presented as the immensely slow unfolding of what was, nevertheless, a divine plan. It allowed for cultural evolution, of primitive societies evolving towards Christianity. “Development” defended the breach until the year beforeMiddlemarch. In 1871 Darwin’s The Descent of Man overturned the concept of humanity as a unique creation, distinct from the animals. After that, development was doomed.
So mythography as a subject finally died at the end of the 19th century, or rather it dissolved into the ectoplasmic haze of theosophy, and echoed faintly in the new, secular anthropology. James Frazer’s popular The Golden Bough (1890) explained myth as a primitive stage from which society progressed, passing through religion and arriving at last at science.