"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
The child was diseased at birth - stricken with an hereditary ill that only the most vital men are able to shake off. I mean poverty - the most deadly and prevalent of all diseases.