When presenting his ideas against the prevailing influences of catastrophism and progressive creationism, which envisaged species being supernaturally created at intervals, Darwin needed to forcefully stress the gradual nature of evolution in accordance with the gradualism promoted by his friend Charles Lyell.
Cando presentou as súas ideas contra as influencias daquela prevalecentes do catastrofismo e creacionismo progresivo, que consideraban as especies como creadas de forma sobrenatural a intervalos, Darwin necesitaba forzosamente enfatizar a natureza gradual da evolución de acordo co gradualismo promocionado polo seu amigo Charles Lyell.