When the first European explorers reached Polynesia in the 1700s they discovered a relatively homogenous group of peoples (the Polynesians) spanning a vast area larger than the Continental United States. Polynesian settlers had managed to establish colonies on every habitable bit of rock in the Pacific, with very few exceptions. Later explorers revised this opinion: even some of the uninhabited islands showed signs of previous habitation, including extensive fallow fields and a number of overgrown statues. These islands came to be known as the Pacific's Mystery Islands. This Entry will cover the course of events which led to the abandonment of one such island, Henderson Island in the Pitcairn Island Group.
A Bit of Geography (and Geology)
The Pitcairn Island Group1 is an isolated cluster of four islands in the South Pacific: Pitcairn, Ducie, Oeno, and Henderson. None of the four were inhabited at the time of European discovery, although Pitcairn was later occupied by the mutineers of the HMS Bounty. Henderson is located at 24° 22' S, 128° 20' W and is an island of the type referred to as Makatea. This means that it is a former coral atoll which has risen from the sea due to lowered sea levels in recent millennia. It is covered with broken limestone, which is called karst. It is also very small, only 14 square miles (37 square km) in area. The soil supports a variety of thick, woody shrubs which make moving about the island almost impossible, but no trees. It was also originally home to 12 bird species, nine of which were flightless. The oceans were generally sparse in terms of shallow water fish and shellfish due to the isolation of the island. All this sets the scene for Henderson's human story.
Archaeological evidence indicates that Henderson may have been visited and used as a temporary shelter en route to more hospitable lands by Polynesian traders as early as the 600s AD. The first permanent settlement was made at some point around 800 AD. Although the settlers probably carried with them all the standard Polynesian plant and animal foods and cleared gardens as their ancestors had when first colonizing other islands, only a few relatively minor crops2 survived and competition for space and resources resulted in all domesticated animals dying out. The lack of wood meant that the settlers had to make their homes in natural caves and rock shelters rather than building houses. Overall it was a meagre existence.
The Economy of Henderson
What is fascinating about life on Henderson is that there was any. That is, the mere capacity of human beings to survive under any conditions is what really stands out from this entire story. One of the main reasons for this survival was a longstanding Polynesian tradition of food surplus. Islands that were capable of supporting 5,000 people with little effort on the part of the citizens would be transformed by large-scale mobilisations of labour on the part of the chiefs to produce enough food for 10,000. This would allow the population of the island to increase to perhaps 7,000 and also provide a food surplus which could be traded to other islands in return for naturally-existing food sources, stone for tool-making, or rare valuables.
In the case of the Pitcairn Island Group, none of the four islands had the capacity for any real substantial agriculture3 but the entire group was connected into a larger trade network which included the (relatively) large island of Mangareva4. Into this network Mangareva exported cultivated crops, mostly taro (Alocasia cucullata), yam (Dioscorea sp) and bananas (Musa sp). The shells of the black-lipped pearl (Pinctada margaritifea) are also exported for making fishhooks. Pitcairn happened to be the site of an excellent quarry and so exported large quantities of rock, especially basalt and obsidian.
Henderson had neither crops nor usable stone, but the inhabitants obtained both in trade for their two exports: meat of the Green Sea Turtle (Chelonia mydas) which bred on the shores of Henderson annually every January to March and, more importantly, the bright red feathers of the lory (Vini stepheni) and fruitdove (Ptilinopus insulariis) which were in high demand as status symbols allowed only to those of chiefly classes but had been wiped out on virtually every other island in the Pacific. In other words, this society of several hundred people survived almost entirely on the export of red feathers.
The Beginning of the End
Although it may be clear to us that a population based upon such a fragile lifeline is inherently unstable, this model actually worked quite well. Life as just described, of a few hundred settlers living in caves, hunting red birds, and trading their feathers for food whenever a trading canoe pulled up to the shore, continued for just about 600 years. Around the year 1400 AD a number of factors led to the contraction of trading spheres across Polynesia. At about this time, Mangareva underwent a severe environmental and cultural collapse similar to the one which destroyed Easter Island society. This collapse was partially the result of many centuries of supporting the population of nearby islands.
The combination of these two factors (the contraction of trading spheres and the Mangareva collapse) cut off incoming food to Pitcairn and Henderson. Soon afterward, native bird species such as the storm-petrel (Nesofregetta fuliginosa), the pigeons (Ducula pacifica) and D galeata as well as the lory and fruit dove mentioned in the last section became extinct, probably due to over-hunting. The size and number of Green Sea Turtles and of Cerithium tuberculiferum (C rubus), a mollusc harvested for food, decreased dramatically. Additional evidence for the elimination of trade is that tools after 1400 AD were made of the shell of the Tridance Clam (Tridacna maxima), which is greatly inferior to basalt in quality. In other words, after the elimination of outside supplies the inhabitants of Henderson had to rely on poor quality local materials and insufficient local food sources.
After about 1450 AD there is no longer any evidence of settlement on Henderson Island. Whether the inhabitants died out or packed up and left in search of more habitable lands is unclear. What is clear is that the solution to this mystery tells a dramatic tale for the modern world about the fragility of societies dependant on trade. Interconnection with other societies is at once a safety net to support us when we fall on bad times and a false support that can put us in a position of weakness by causing us to grow beyond what our local environment can support. International trade is arguably a requisite for modern civilisation, but the potential risks of such a system should never be ignored or forgotten.