When Joseph Conrad wrote in Heart of Darkness that he was going back in time as he went into Africa, he did not just mean that he was going back in historical time. He meant that he was going back in evolutionary time. Africans were literal biological specimens of what whites had once been. President Theodore Roosevelt described Africans in evolutionist terms that are both unilinear and racist. In the foreword to his collection of dispatches from East Africa, he notes that "the dark-skinned races that live in the land vary widely. Every human body part was measured to "prove" that Africans, Asians, and Indians were separate species. The Western evaluation of the Mangbetu and their neighbors is duplicated for African groups everywhere. In religious studies, for example, use of magic and witchcraft, worship of multiple gods, and reverence for ancestors were considered not only backward but irrational.