We know that the Zanj (blacks) are the least intelligent and the least discerning of mankind, and the least capable of understanding the consequences of actions.
Al-JahizLike the crow among mankind are the Zanj [African Blacks] for they are the worst of men and the most vicious of creatures in character and temperament.
Al-JahizAnimals engage in a struggle for existence; for resources, to avoid being eaten and to breed. Environmental factors influence organisms to develop new characteristics to ensure survival, thus transforming into new species. Animals that survive to breed can pass on their successful characteristics to offspring.
Al-Jahiz