
As many know, I straddle the fine line between ‘interested’ and ‘obsessed’ with South Pacific history and island biogeography. One of my favourite subjects is the terrible interlocked fates of Pitcairn, Mangareva, and Henderson Islands. Have you guys heard this one?
The simplified version goes like such: three islands are strung out in the middle of dang nowhere, the remotest of remote southeast Polynesia. The largest is Mangareva, which prior to human settlement had pretty much everything a little clan of roving Polynesians could want to support life: good soil, large trees for canoes, fresh water, and abundant large-shelled oysters for fishhooks and ornaments. It lacked high-quality stone for making adzes to take advantage of the trees and soil (you can’t make a plough with coral), but that was fine, because a neighbouring island - Pitcairn - had plenty of the right kind of rock.
Now Pitcairn, prior to its pyrite fame as the homeplace of the Bounty mutineers, also had a small population of Polynesians. It had glass-based volcanic rock for sharp tools, and fine-grained basalt for adzes, cooking stones, and so forth. However, it was pathetically tiny - barely two miles across - didn’t have reliable freshwater, and instead of long sloping beaches, Pitcairn had sharp cliffs that were almost impossible to fish off of. In particular, no large oysters were available. In 1856, by the time the mutineers’ descendants were pretty much settled in, the 194 people living there had exhausted their carrying capacity and had to be rescued by the British government. Very little agricultural land was available even before that, which is when this story takes place.
The final island, Henderson, was an upthrust coral reef. It didn’t have trees big enough to make canoes, its porous coral bedrock soaked up most of the fresh water, and razor-sharp limestone outcroppings could cripple a barefoot traveller in minutes. However, it did have abundant food in the nearby reef; fish practically fought themselves onto hooks, and the plentiful seabirds and turtles were luxury goods for Polynesian societies.
So, plainly put, societies on each geographically-isolated island could only survive by trading with the other islands for the things they were lacking. Stone, trees, food, marrigeable children, technical skills, livestock, etc, etc.
Here’s where it gets scary.
Trade continued until about 1500 A.D., the date from which diligent archaeologists and their whiny grad students cannot find traded goods from other islands. The canoes had stopped arriving. The problem was the worst for Henderson, whose fairly large and unsustainable population was now essentially trapped without the basics of life. They had no metal, no large trees to make canoes, and no stones other than coral-based limestone. They struggled by for a couple of generations with oven stones that cracked at the slightest heat, scanty water, tiny fishhooks, and bird bones. Several species of land birds became extinct, and aquatic life around the bay was rapidly depleted. By 1606, the entire population had died.
Why was Henderson doomed? Obviously, trade had ceased. But one step further back asks why trade had ceased. Pitcairn and Mangareva - also struggling for survival at this time - had condemned everyone on Henderson Island to death by beating the hell out of their own islands. Deforestation had caused all the topsoil on the other two islands to wash away, rendering agriculture difficult or impossible; free-roaming feral pigs were eating the nutritious roots and forbs the islanders depended on; no trees large enough to build canoes remained. People turned to cannibalism and tyranny, and the disorganized societies could not muster the resources to trade even if they had had goods to trade any more.
The mind cringes to think how the populations of Pitcairn (for all its people died as well) and Henderson perished. Mass murder? Internal warfare? Cannibal feasts? Incest, surely, and lingering deaths, and infanticide; perhaps they dwindled away quietly together. Perhaps they all went mad and built rickety rafts to float out to sea in hopes of finding another island large enough to support them. But Tahiti was a thousand miles away, and without the material to build proper double-hulled canoes, their makeshift crafts would never have found land in time.
So what’s the moral of this story?