Carnegie party inspecting one of the moai (giant statues), 1916

That you can now fly here in five hours, several days a week from Santiago, Chile, belies the truth that Easter Island is the most isolated of inhabited places on Earth. The nearest neighbor, Pitcairn — where the Bounty mutineers settled — with a population of a mere 48 people, is 1,240 miles to the west.

Significantly, it is this preternatural lonesomeness that suggests the answers to two of archaeology’s greatest riddles: the giant and eerie stone carvings for which the island is renowned, and the ecological disaster that caused a 99% population decline and made Easter Island a poster child for the fate many believe awaits the whole of humanity if we’re not careful.

But first, the heads.

Archaeologists have inventoried 887 carved figures made between about A.D. 1000 and 1600. These big busts, called moai, are an average of 13 feet tall and are known to islanders as the “living faces.” They represent ancestors and elders. “For us, they are people,” one descendant of the natives told me.

Perhaps. But for me they are just ancient and alien statues. Their meaning isn’t intrinsic at all — it is abstract, intense and interrogative: I want to sit at their feet and ask questions. I feel these guys know something, and I want to know it too. Gigantic and primitive, the moai provoke not reverence or awe but pure wonder, registered as a definite physical sensation, a kind of cosmic “Huh?”

Such ethereal queries are accompanied by terrestrial ones, such as: How did the moai get from the single quarry where they all were carved to their erect positions — mostly dotted around the coastal perimeter with their backs to the sea — up to 12 miles away? Several theories have been demonstrated as feasible, including dragging the statues on wooden sleds. “There are lots of ways they could have been moved,” says Sergio Rapu, the only born Easter Islander who is also a trained archaeologist. “‘How was it actually done?’ is the question.”

Oral history claims that the statues walked, and Mr. Rapu believes he has found examples of the “shoes” they wore for the journey: stones, flat on the topside, used by the islanders to pivot a trussed-up statue back and forth and forward — like moving a refrigerator — while synchronizing their exertions with chanting. Some experiments show a convincing way the moai, if lashed upright into a wooden frame, could have marched themselves along practically under their own power, as though hobbling on crutches. In truth, islanders may have used a combination of techniques.

And why did they make so many? Well, why not? Easter Island, in the relative far east of the Pacific Ocean, 2,360 miles from South America, was one of the very last places to be settled by Polynesians. People arrived around the year 500, and after several generations the population was sufficient to get into the labor-intensive monument business. Polynesians were carvers anyway; here they had the perfect volcanic rock for it and little else to occupy their time. So statue building became the central activity of Easter’s society. Unsurprisingly, the maximum population of 15,000 to 20,000, reached in the 15th or 16th century, corresponds to the peak of moai-making.

Unluckily, the native Rapa Nui were living in one of the most fragile ecosystems imaginable: a windy, cool climate, very dry by tropical standards. Deforestation set in almost from the outset, caused by a combination of factors: animals eating the seeds of trees; fires; El Niño-induced droughts; salt spray; and human consumption of wood.

Mr. Rapu, who was also governor of the island for six years, says that the deforestation was undoubtedly a mixture of human and natural forces. By the time Dutch Admiral Jacob Roggeveen spotted the island on Easter Sunday in 1722 (there’s one secret revealed for you), he found no trees taller than 10 feet.

The major obvious fallout from Easter’s deforestation was diminution of the food supply. The archaeological record shows that the islanders’ diet changed from big porpoises — which had to be caught far from shore using canoes they no longer had — to small mollusks gathered from tidal basins; birds were hunted to extinction; and cannibalism became rife. Jared Diamond, who uses Easter as a case study in his book “Collapse,” reports that “Your mother’s flesh sticks in my teeth” became a common insult.

For the Easter Islanders, there was no escape. “They were trapped,” says Mr. Rapu. In or around 1680, we know, civil war broke out. People began tearing down the statues, possibly in deliberate effrontery to leaders they believed had failed them. (A 33-foot tall statue named Paro, dating from about 1620, was one of the last erected and one of the last felled.) The year 1838 offers the last European mention of a standing statue, and in 1868 every moai on Easter Island was either toppled in the dirt or resting stillborn in the quarry.

Captain Cook, arriving in 1774, described the islanders as “small, lean, timid and miserable.” European diseases arrived soon after, killing more people, and slave raids in 1862-63 carried off 1,500 Rapa Nui — half the remaining population — to the Peruvian guano mines. A handful managed to struggle home a few years later — and brought the plague with them. By 1872 there were just 111 people on the island.

Today, the 3,800 residents in Rapa Nui are citizens of Chile, the islanders having accepted Chilean annexation in 1888. It’s been for the most part a happy relationship. Spanish is the island’s lingua franca (though Rapa Nui is being revived), and you can have a mean plate of ceviche con coco while you contemplate the fate of the island and its lessons.

Due to the massive population drop-off, vast swaths of cultural knowledge have been lost forever, contributing to the sense of insolubility that surrounds Easter’s puzzling past. Says Mr. Rapu: “Our ethnography is one of the poorest in the Pacific. But we still know how to fish. We still know how to track the moon for guidance in planting. We still have some things to call ourselves Rapa Nui.” Above all — and for all of us — they have the moai, about which no matter how much archaeologists surmise, we shall always be left wondering.

Jeremy Hildreth
Wall Street Journal