Complex sentence: He reasoned that black Africans were very different from white Europeans, although e did speculate on the admixture of Aryan or Hamitic blood arising from the advent of Islam among the Hausa and Fulani.
Split into simpler sentences: He reasoned that black Africans were very different from white Europeans. He did speculate about the admixture of Aryan or Hamitic blood arising from the advent of Islam among the Hausa and Fulani.