Collapse_ How Societies Choose to Fail or Succeed - Jared Diamond [180]
The main food products of these orchards, swamps, and fields are starchy plant foods. For their protein, in the absence of domestic animals larger than chickens and dogs, traditional Tikopians relied to a minor extent on ducks and fish obtained from the island’s one brackish lake, and to a major extent on fish and shellfish from the sea. Sustainable exploitation of seafood resulted from taboos administered by chiefs, whose permission was required to catch or eat fish; the taboos therefore had the effect of preventing overfishing.
Tikopians still had to fall back on two types of emergency food supply to get them over the annual dry season when crop production was low, and the occasional cyclone that could destroy gardens and orchard crops. One type consisted of fermenting surplus breadfruit in pits to produce a starchy paste that can be stored for two or three years. The other type consisted of exploiting the small remaining stands of original rainforest to harvest fruits, nuts, and other edible plant parts that were not preferred foods but could save people from otherwise starving. In 1976, while I was visiting another Polynesian island called Rennell, I asked Rennell Islanders about the edibility of fruit from each of the dozens of Rennell species of forest trees. There proved to be three answers: some trees were said to have “edible” fruit; some trees were said to have “inedible” fruit; and other trees had fruit “eaten only at the time of the hungi kenge.” Never having heard of a hungi kenge, I inquired about it. I was told that it was the biggest cyclone in living memory, which had destroyed Rennell’s gardens around 1910 and reduced people to the point of starvation, from which they saved themselves by eating forest fruits that they didn’t especially like and normally wouldn’t eat. On Tikopia, with its two cyclones in the average year, such fruits must be even more important than on Rennell.
Those are the ways in which Tikopians assure themselves of a sustainable food supply. The other prerequisite for sustainable occupation of Tikopia is a stable, non-increasing population. During Firth’s visit in 1928-29 he counted the island’s population to be 1,278 people. From 1929 to 1952 the population increased at 1.4% per year, which is a modest rate of increase that would surely have been exceeded during the generations following the first settlement of Tikopia around 3,000 years ago. Even supposing, however, that Tikopia’s initial population growth rate was also only 1.4% per year, and that the initial settlement had been by a canoe holding 25 people, then the population of the 1.8-square-mile island would have built up to the absurd total of 25 million people after a thousand years, or to 25 million trillion people by 1929. Obviously that’s impossible: the population could not have continued to grow at that rate, because it would already have reached its modern level of 1,278 people within only 283 years after human arrival. How was Tikopia’s population held constant after 283 years?
Firth learned of six methods of population regulation still operating on the island in 1929, and a seventh that had operated in the past. Most readers of this book will also have practiced one or more of those methods, such as contraception or abortion, and our decisions to do so may have been implicitly influenced by considerations of human population pressure or family resources. On Tikopia, however, people are explicit in saying that their motive for contraception and other regulatory behaviors is to prevent the island from becoming overpopulated, and to prevent the family from having more children than the family’s land could support.