In the zoology field of biology, Muslim biologists developed theories on evolution which were widely taught in medieval Islamic schools. John William Draper, a contemporary of Charles Darwin, considered the "Mohammedan theory of evolution" to be developed "much farther than we are disposed to do, extending them even to inorganic or mineral things." According to al-Khazini, ideas on evolution were widespread among "common people" in the Islamic world by the 12th century.
The first biologist to develop a theory on evolution was al-Jahiz (781-869). He wrote on the effects of the environment on the likelihood of an animal to survive, and he first described the struggle for existence. Al-Jahiz was also the first to discuss food chains,and was also an early adherent of environmental determinism, arguing that the environment can determine the physical characteristics of the inhabitants of a certain community and that the origins of different human skin colors is the result of the environment.