Climate's effect on people

Ibn Khaldun determined that the fourth climate is the most temperate of the climates, so its people are the most temperate in bodies, colour, character, and religion. Prophecy is found mostly in it, and he knew of no mission in the southern or northern climates. He held that blackness among the people of the first and second climates results from the temperament of their air, because of the doubled heat when the sun is directly overhead twice a year. It is not due to Noah's curse on Ham, as some genealogists imagined from the tales of the storytellers. Noah's prayer was that Ham's son should become a slave to the sons of his brothers, and it does not mention blackness. Similarly, whiteness, reddishness, blue eyes, and reddish hair are found among the people of the sixth and seventh climates, because of excessive cold. He made an exception for the Arabian Peninsula to the rule of deviation, because the seas surround it on three sides, so its humidity affects the humidity of its air. He also mentioned that the people of Mali, Kukaw, and Takrur, who border the land of the Maghrib, adopted Islam in the seventh century. ²

What is not recorded here needs a further source.