Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [58]
We would of course love to know exactly when Easter Islanders erected their first statues, and how styles and dimensions changed with time. Unfortunately, because stone cannot be radiocarbon-dated, we are forced to rely on indirect dating methods, such as radiocarbon-dated charcoal found in ahu, a method known as obsidian-hydration dating of cleaved obsidian surfaces, styles of discarded statues (assumed to be early ones), and successive stages of reconstruction deduced for some ahu, including those that have been excavated by archaeologists. It seems clear, however, that later statues tended to be taller (though not necessarily heavier), and that the biggest ahu underwent multiple rebuildings with time to become larger and more elaborate. The ahu-building period seems to have fallen mainly in the years A.D. 1000-1600. These indirectly derived dates have recently gained support from a clever study by J. Warren Beck and his colleagues, who applied radiocarbon dating to the carbon contained in the coral used for files and for the statues’ eyes, and contained in the algae whose white nodules decorated the plaza. That direct dating suggests three phases of construction and reconstruction of Ahu Nau Nau at Anakena, the first phase around A.D. 1100 and the last phase ending around 1600. The earliest ahu were probably platforms without any statues, like Polynesian marae elsewhere. Statues inferred to be early were reused in the walls of later ahu and other structures. They tend to be smaller, rounder, and more human than late ones, and to be made of various types of volcanic stone other than Rano Raraku tuff.
Eventually, Easter Islanders settled on the volcanic tuff from Rano Raraku, for the simple reason that it was infinitely superior for carving. The tuff has a hard surface but an ashlike consistency inside and is thus easier to carve than very hard basalt. As compared to red scoria, the tuff is less breakable and lends itself better to polishing and to carving of details. With time, insofar as we can infer relative dates, Rano Raraku statues became larger, more rectangular, more stylized, and almost mass-produced, although each statue is slightly different from others. Paro, the tallest statue ever erected, was also one of the latest.
The increase in statue size with time suggests competition between rival chiefs commissioning the statues to outdo each other. That conclusion also screams from an apparently late feature called a pukao: a cylinder of red scoria, weighing up to 12 tons (the weight of Paro’s pukao), mounted as a separate piece to rest on top of a moai’s flat head (Plate 8). (When you read that, just ask yourself: how did islanders without cranes manipulate a 12-ton block so that it balanced on the head of a statue up to 32 feet tall? That is one of the mysteries that drove Erich von Däniken to invoke extraterrestrials. The mundane answer suggested by recent experiments is that the pukao and statue were probably erected together.) We don’t know for sure what the pukao represented; our best guess is a headdress of red birds’ feathers prized throughout Polynesia and reserved for chiefs, or else a hat of feathers and tapa cloth. For instance, when a Spanish exploring expedition reached the Pacific island of Santa Cruz, what really impressed the local people was not Spanish ships, swords, guns, or mirrors, but their red cloth. All pukao are of red scoria from a single quarry, Puna Pau, where (just as is true of