As you know, most of Third World countries were actually regions in Europe's empires. Look at all the "clean" borders at Afrika to see what I mean. This creates a very bad situation, where diffrent Ethnical groups and religions are stuck in a single country while others are splitted.
Now, imagaine to yourself that during the De-Colonization there was an expedition, painting a map of new African states that their neighbors are the most close together by Culture, Ethnical origins, Religion, etc. Minor Transfers to let the states have sea access and territorial sequence are allowed. If they would give the map they drew to the UN, how would it look like?
Good luck!