Born in Geneva, Switzerland, Bonnet studied law, gaining his doctorate in 1743. In the same year he was elected a fellow of the Royal Society for his work on regeneration in lower animals and his demonstration of breathing pores (stigmata or spiracles) in caterpillars and butterflies. He is chiefly remembered however for discovering parthenogenesis (reproduction without fertilization) in the spindle-tree aphid and for the ideas on evolution he proposed following this observation.

Bonnet believed all organisms are preformed and that the germs of every subsequent generation are contained within the female. Such thinking implied that species remain constant, leaving Bonnet to explain how species become extinct as evidenced by fossil remains. He argued that the Earth had experienced periodic catastrophes, each destroying many life forms, but the remaining species all evolved to some degree. (Bonnet was the first to use the term ‘evolution’ in a biological context.) Thus after the next catastrophe apes progress to men, and men become angels. The catastrophism theory was adopted by Georges Cuvier, and strongly influenced geological thinking until the 1820s.