Most of the African continent is on a high "plateau". Although it is true that African contains the largest desert in the world, the desert itself is not physically "high" in the same sense.
Human societies from the Paleolithic to the early Neolithic farming tribes lived without states and organized governments. For most of the Lower Paleolithic, human societies were possibly more hierarchical than their Middle and Upper Paleolithic descendants, and probably were not grouped.
The raid took place on October 16, 1859 before the war. Brown was a man determined to abolish slavery, a belief of many northerners. This Revolt was led by an abolitionist, or a person against slavery. The raid indicated that abolitionists would use violence to overthrow slavery. Slavery was a big issue during this time and was a huge reason for the sectionalism between the North and South.