Augustin Pyramus de Candolle was a Swiss botanist. René Louiche Desfontaines launched de Candolle's botanical career by recommending him at a herbarium. Within a couple of years de Candolle had established a new genus, and he went on to document hundreds of plant families and create a new natural plant classification system. Although de Candolle's main focus was botany, he also contributed to related fields such as phytogeography, agronomy, paleontology, medical botany, and economic botany.
De Candolle originated the idea of "Nature's war", which influenced Charles Darwin and the principle of natural selection. de Candolle recognized that multiple species may develop similar characteristics that did not appear in a common evolutionary ancestor; a phenomenon now known as convergent evolution. During his work with plants, de Candolle noticed that plant leaf movements follow a near-24-hour cycle in constant light, suggesting that an internal biological clock exists. Though many scientists doubted de Candolle's findings, experiments over a century later demonstrated that ″the internal biological clock″ indeed exists.