Charles Darwin
Darwin aliendelea na utafiti wa sampuli zake na kutoa masomo mbalimbali na kuyatafakari. 1859 alitoa kitabu kuhusu mageuko ya spishi kwa njia ya uteuzi asilia (On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) alimoeleza nadharia yake.