I shall go further and say that even if an examination of the past could lead to any valid prediction concerning man's future, that prediction would be the contrary of reassuring.
"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.