Sub-Sahara African populations are tall relative to the extremely adverse disease environment and their low incomes. Selective mortality, which removes shorter individuals leaving taller individuals in the population, was proposed as an explanation. From heights of surviving and non-surviving children in Gambia, we estimate the size of the survivorship bias and find it to be too small to account for the tall adult heights observed in sub-Saharan Africa. We propose instead a different yet widely ignored explanation: African populations attain a tall adult stature, because they can make up a significant amount of the growth shortfall after age 5. This pattern is in striking contrast to other developing countries. Moreover, mortality rates are relatively low after age 5 adding further doubts about selective mortality.