According to Tilly: Medieval Africa was...
-Sparsely populated (low returns to agriculture)
- the land itself is not of much value
- sheer distance protects rulers from external rivals
- rulers have little incentive to gain and hold territory or engage in war over territory
- labour (people) is valuable
- so much space allows disgruntled subject to easily exit
- extraction is light and sporadic
- endemic weakness of African state reflects a medieval predecessor that did not need to develop the sinew of the modern states (strong armies and bureaucracies)