However one must understand that there are many intelligent africans and many dumb europeans.  There is only a difference in the frequency of what you can find.  As to the flynn effect, it has been surmised by others that the I.Q. increases are due to better nutrition.  People today are much taller than they were a hundred years ago and have a larger brain size.  This change is solely due to better nutrition.  It has been shown in many studies the nutritional deficienciess can lower I.Q..  However, having a higher i.q. means that you can get better nutrition for your child and thus add even more i.q. points.  So africa's average I.Q. of around 70 is lower than it's potential as evidenced by american blacks who have an I.Q. of about 85.  However this is probably the upper limit as to what african blacks could achieve since there is significant white admixture in american black populations.  Studies of adopted children have shown that asian children tend to have I.Q.'s significantly greater than their adoptive parents (110)  while black children have I.Q.'s that are lower than their adoptive parents (90).  So evidence points to the I.Q. gap being at least partially genetic.