Adversity makes you stronger.
Straight out of Toynbee's theory of history.
Cultures which emerged in environments that held no challenges failed to develop. See Wu River culture, China.
Cultures which emerged in environments that held significant -- but overcomable -- challenges led to highly developed states. See Indus Valley culture, sub-continent.
Cultures which emerge in environments that are extremely adverse, where simply getting by is a challenge -- fail to develop. See Eskimo culture, North America.
As applied to Africa, there are probably examples of the former and the latter -- but few of the happy medium.