Do three Pacific islands provide lessons for achieving a sustainable human population?

These islands were more-or-less isolated, microcosms that perhaps tell us what is going to happen with the global population. Anthropological accounts also describe remarkable forms of birth control. Do they tell us anything about how to achieve sustainable populations today?

By Frank Götmark

 

Easter Island, and historical background

One of the most debated questions in island historical research concerns the fate of people living on Easter Island, or Rapa Nui. This island of 164 km² is one of the most isolated in the world, located in the southeastern Pacific Ocean. Research shows that the inhabitants had cleared the forest on the island before 1650, which meant that canoes could no longer be built for fishing or catching seabirds and collecting eggs on nearby islets. People had to rely more on risky agriculture on the barren island. When Captain Cook arrived in 1774, his crew met inhabitants that were in poor condition. Strong population decline is part of the story. However, there were earlier visits by Europeans, the first in 1722 and there is debate about how these visits affected the islanders through disease, murder, slave raiding and other conflicts. The case of Rapa Nui is often used as a warning about humanity’s future and the costs of ecological overshoot.

Some human populations on Pacific islands managed to use resources sustainably over long periods, at least partly by keeping their populations stable. Even then, however, human colonization tended to decrease biodiversity initially. The remarkable extinction of birds on Pacific islands rivals the late Pleistocene extinction of large mammals in North America: thousands of bird populations and about 2000 bird species disappeared as the islands were colonized by people over time. Many of these birds were flightless; they lacked natural predators, did not flee from humans, and so were easy prey.

 

Tikopia in the southwestern Pacific

Tikopia is a small (ca 4.6 km²) island in the Solomon Islands, and is less isolated than Easter Island, but still an outlier in this island country. Tikopia is 380 m high and contains a volcanic lake 80 m deep. Anthropological and archeological evidence suggests that human colonization about 3000 years ago destroyed much the island’s wildlife and natural habitats, but that a human society with a more-or-less stable population developed over time (see refs 1-7 below). During an initial period of more than 900 years, slash-and-burn agriculture dominated, and several birds, fruit-bats, and turtles became extinct. Fish and shellfish were decimated.

Sometime between 100 BC to AD 300, a second phase with a new form of agriculture emerged, a complex system of fruit and nut trees forming an upper canopy, with aroids, yams, and other shade tolerant crops under these. Husbandry of pigs began during this phase, and probably also population control (see below) on the densely inhabited island.

A third phase around AD 1200 started with some new settlers of Western Polynesian culture. Around AD 1600, pigs were eradicated, stocks of fish, shellfish and turtles had partly recovered, and measures to prevent overpopulation were introduced. Tikopians used six population control measures: 1) traditional contraception, such as coitus interruptus, 2) celibacy, for instance heads of family ordered young men not to marry, 3) abortion for extramarital pregnancies, e.g. by placing hot stones on women’s stomachs, 4) infanticide, decided by the father, 5) suicide, with “swim away” most common, and 6) banishment, by chief’s order in case of crime, or by sea voyage during famines, e.g. after a typhoon.

Population control appears to have ensured a sustainable society during many hundred years (sometimes interrupted by droughts or typhoons). The population was kept at a maximum of about 1,200 persons (ca 260 per km², slightly denser than Germany today). Christian missionaries ended the custom of population control, from about 1907 onwards. The population then increased from 1,200 to 1,800 in 1950, which led to migration to other islands. Soil productivity remains good, however, and the intensive agricultural system may not lead to long-term setback, “provided there is no substantial increase in the resident (de facto) population.” ²

A recent study of Tikopia⁵ used stable isotope analysis of commensal pig and Pacific rat remains from archaeological sites. It confirmed that the second developmental phase led to dramatic restructuring of the island’s ecosystem. Slash-and-burn agriculture was replaced by a multistory agricultural system which mimicked natural forest cover through replacing native species with introduced crops. The authors refer to “structural substitution, ecomimicry, a strategy which maintains existing ecosystem structure but alters species compositions to increase production of food and other biocultural resources”. But it is important to remember that the native biota had already been mostly lost, limited to steep slopes for plants and some birds⁷. According to the authors⁵, “the Tikopia case study may offer some insights towards global sustainability… [but] today the greatest threats… come not from the Tikopians themselves, but from forces of global climatic change”.

 

Abortion on Taiwan

A remarkable form of birth control, mandatory massage abortion, was practiced at least up to 1628 by the Sirayan population in southernmost Taiwan (36 200 km², formerly Formosa). Even more remarkable, women were not allowed to give birth until an age of about 31-36 years. Any pregnancy before that age was ended at a relatively early stage by strong massage of womb and uterus. Priestesses in the villages, considered to have religious (supernatural) power, conducted these abortions. They visited pregnant women during a few days, to induce uterine contraction by massage, cutting off blood circulation and causing death of the fetus, with subsequent abortion. This was painful yet accepted, and perhaps not more painful or with more risks for women than giving birth. The abortion system, described by the Dutch missionary Candidius in 1628, was considered by Malthus and others as a form population control responding to island conditions.

In a detailed analysis, J R Shepherd⁸ suggests that massage abortion was not due to the need for population control, but a logical part of Sirayan social organization. Population density was relatively low, food readily available (agriculture combined with a high density of deer), with no evidence of starvation among the villagers. One might object that these healthy conditions could have been the result of population control. Shephard does not discuss this possibility.

Men and women lived in separate houses, and men married a (younger) woman at the age of 20-21. However, men did not take up residence with their wives until much later, at an age of 40-50. Men had two main functions, deer hunting and warfare against other villages, with headhunting indicating high status. The absence of family life and the birth control system allowed young men to become extra skillful and successful in warfare, according to Shephard.

Women and men mainly lived separately, but married women could be visited by partners (and other men) at night, and sex was allowed. Women were in charge of agriculture, had considerable power through the priestesses (that could call for rain and good harvests, for example) while men, in local meetings, solved some disputes. Similar social organization occurred among other population groups on the island, but it seems that only Sirayans practiced mandatory abortion. Shepherd suggests it followed from the strong separation of men and women, and an “age grading system” for men, whereby they could attain status and finally, when old, could move to the women’s house. As old men there, they posed no threat, and childbearing was allowed for their wives.

But how did massage abortion first arise among the Sirayans on southern Taiwan? My own guess is that it came with immigrants or other influences from the southeast Asian mainland, where massage abortion has been practiced for more than 2000 years. It is still common in Thailand and elsewhere (for evidence see Potts et al. 2007⁹). The Sirayan language is part of the Austronesian language family¹⁰, so connections to the southeast Asian mainland have existed and cultural exchange would have been inevitable.

The Dutch instituted Christian marriages among the Sirayans and other aboriginals on the island in the seventeenth century. Shephard thinks that women welcomed, or at least accepted this new Christian form of marriage. However, by 1661 the Dutch were ousted from Taiwan by Zheng Chenggong. Many converts in Taiwan were only nominal Christians, and after the defeat of the Dutch, Zheng succeeded in eradicating the new religion¹⁰.

 

Are there any lessons to be learned for people on continents, or indeed for humanity globally? Even seemingly isolated islands are in practice not isolated but influenced by migration and new cultures. Culture obviously plays an important part in population policies. On continents, with several or many countries, ethnic groups often feel the need to outbreed their rivals, even though this is a mutually destructive strategy. A sense of mutual trust and unity of purpose can be difficult to achieve on territory that is already crowded and contested. However, this must be the goal since acceptance of small families and population decline is a prerequisite for sustainable development.

 

Acknowledgements – My text about the Sirayan population was stimulated by an interesting paper by GuiGiu Yao and Robert J. Wyman¹¹ where they mentioned the work of Shepherd and Potts et al. Yao and Wyman suggest that religion was an important part of birth control among the Sirayans, and it is fascinating that both religion and abortion was in the hands of women (the priestesses). I thank Richard Grossman, Ole Mertz and Nicola Turner for comments on the text.

 

References (see also in-text Internet links)

¹Gowdy JM (2006). Darwinian selection and cultural incentives for resource use: Tikopia as a case study of sustainability. Int. J. Global Environmental Issues 6: 348-361.

²Mertz O (2010) Sustainable land use in Tikopia: Food production and consumption in an isolated agricultural system. Singapore Journal of Tropical Geography 31: 10–26.

³Kirch PV & Swift JA (2017) New AMS radiocarbon dates and a re-evaluation of the cultural sequence of Tikopia island, southeast Solomon Islands. The Journal of the Polynesian Society 126: 313- 336

⁴Bódi B & Takács-Sánta A (2021) Hardin’s Mistake: Tikopia, the Society That Avoided the Tragedy of the Commons, World Futures 77: 205-221.’

⁵Swift JA et al. (2021) Stable Isotopic Evidence for Nutrient Rejuvenation and Long-Term Resilience on Tikopia Island (Southeast Solomon Islands). Sustainability 13, 8567.

⁶Wikipedia (2023), Tikopia. Accessed 4 February.

⁷Steadman DW, Pahlavan DS & Kirch PV (1990). Extinction, biogeography, and human exploitation of birds on Tikopia and Anuta, Polynesian outliers in the Solomon Islands. Bishop Museum Occasional Papers 30: 118-153.

⁸Shepherd, J R (1995). Marriage and mandatory abortion among the 17^th-century Siraya. American Ethnological Society Monograph Series, Number 6. American Anthropological Association, Arlington, VA 22203, USA.

⁹Potts M, Graff M & Taing J (2007). Thousand-year-old depictions of massage abortion. J Fam Plann Reprod Health Care 33(4): 233-4.

¹⁰Adelaar KA (2007). Siraya, Taiwani’s oldest written language In Storm C & Harrisson M (Eds) The Margins of Becoming: Identity and Culture in Taiwan (Studia Formosiana), 20 pp (available at Researchgate).

¹¹Yao, G & Wyman, RJ. 2017. Population. In: Jenkins W et al (Eds). Routledge handbook of Religion and Ecology, pp 304-315.