Karl Fedorovich Kessler

Karl Fedorovich Kessler (19 November 1815 – 3 March 1881) was a German-Russian zoologist and author of zoological taxa signed Kessler, who was mostly active in Kiev, Ukraine and conducted most of his studies of birds in Ukrainian regions of the Russian Empire - Kiev Governorate, Volyn Governorate, Kherson Governorate, Poltava Governorate and Bessarabia. He also studied the fish of the Dniester, Dnieper, and Southern Bug rivers, and on the Ukrainian coast of the Black Sea.

Kessler was one of the first zoologists to propose that mutual aid, rather than mutual struggle, was the main factor in the evolution of a species. The anarchist Peter Kropotkin later developed this theory in his book Mutual Aid: A Factor of Evolution.