Adding to Little Hawks comments, countries like D. R. Congo comprise many different groups, thrown together under a government that is weak and unresponsive to needs. Boundaries are artificial, throwing diverse groups together, determined by the colonial powers that have gone home.
Competition and war between groups seeking power (or just to have self-rule in their own corner of the 'country') becomes inevitable.

Inevitably, the 'more children the better' rule prevails- more hands to help feed the family, more children to sell, and more bodies to replace those that die young.