From possible disappearance to a mix: the ecological model of Easter Island

Easter Island is located at a point of the Polynesian triangle in the Pacific Ocean, and is the most geographically isolated population in the world. The Rapanui ethnic group colonised the island between the 5^th and 10^th centuries, and developed their original culture from a small group of individuals who spoke an austronesic language. The growth of the population, together with their isolated situation and the geographical impossibility of emigrating to other islands, led the population to collapse, being an ecological reference model for growth limits and sustainability capacity.

It may have been the fight for survival among clans which led to the end of the moais (statues) culture, and when “contact” with Europeans happened in the 18^th century, cultural changes and a decline in the population had already occurred. But external human exploitation could have totally exterminated the Rapanui tribe when a group of pirates abducted a thousand natives in 1862 to use them as slaves in Peru collecting guano. International pressure ended mistreatment, but many had already died and those who were able to return brought infectious diseases with them which decimated the remaining population. So a bottleneck was reached of 110 inhabitants in 1877. It might have signalled the end of the population, but fortune smiled on the small group of Rapanuis and during the 20^th century the population grew, reaching 456 individuals in the 1934 census and over a thousand in 1960.

However, the reduced number of ancestors at the end of the 19^th century meant a possible increase in consanguinity for later generations, due to inbreeding. A study of Rapanui and foreign surnames in the evolution of births during the 20^th century shows that after the opening of Easter Island to the world in 1965 exogamous births predominate, reflecting the general mixing of Rapanuis and foreigners. Surnames are a good indicator of an individual’s origins and of the evolution of biodiversity and mixing in a population.

Towards the end of the 19^th century there were 86 different Rapanui surnames, which had fallen to 77 in 1934. For births between 1937 and 1965, 37 surnames appear, and this again drops to only 30 among those born after 1965, the date when Rapanui society opens up to the world and to foreign immigration. The values for indices of ecological diversity obtained from surnames of newborns increase as the 20^th century moves on and inbreeding decreases. But although the total number of different surnames has increased considerably due to foreign input, 60 % of surnames of newborns at the end of the century were Rapanui. The population of Easter Island is more diverse, but up to the present century a solid base of indigenous people remained.

According to the census of 2012 there were 5,806 inhabitants, with a census variation which means a con 54 % increase in 10 years. Immigration is causing social and cultural changes: it is threatening the Rapanui language, there are changes in socio-economic activities and aquifers are at risk of being polluted. The demographic change in the population presents a challenge for the 21^st century: preserving Rapanui culture together with the ecological sustainability, both of which are under threat from the strong impact of tourism.

Miguel Hernández Martínez, professor of Biological Anthropology in the Dept. of Evolutionary Biology, Ecology and Environmental Sciences of the University of Barcelona, made between 1994 and 1997 biodemographic field work in Hanga Roa (where the population of Easter Island resides), along with Professor Clara Garcia-Moro, from her same Department. More information about the results obtained in their research can be found at www.didac.ehu.es/antropo