Monboddo struggled with how to "get man from an animal" without divine intervention. This is typical of the kind of thinking which is called "deist". He developed an entire theory of language evolution around the Egyptian civilisation to assist in his understanding of how man descended from animals, since he explained the flowering of language upon the spinoff of the Egyptians imparting language skills to other cultures. Monboddo cast early humans as wild, solitary, herbivorous quadrupeds. He believed that contemporary people suffered many diseases because they were removed from the environmental state of being unclothed and exposed to extreme swings in climate.