Study Clarifies Genetic Origins of Kiritimati Inhabitants

A recently published study in Genome Biology and Evolution provides new insights into the settlement of Pacific islands and the migrations of Austronesian-speaking peoples, helping to understand human movement and cultural interactions in the region.

Kiribati is one of the first nations facing the most devastating impacts of climate change—rising sea levels may cause the island nation to disappear from the world map within the next few decades. Coastal erosion, freshwater salinisation, and extreme weather conditions force residents to seek new places to live.

Kiritimati, part of Kiribati, is an island in the Pacific Ocean located in eastern Micronesia, with a population of just over 5,000. It is the world’s largest coral atoll, covering an area of 388 square kilometres. Archaeological evidence suggests that Polynesians inhabited Kiritimati between 1250 and 1450. However, when Europeans first encountered the island in 1777, it was uninhabited. Later, starting in the 1920s, workers from various islands of the Gilbert Archipelago, also part of Kiribati, were brought to Kiritimati to work in coconut plantations and nuclear testing programs. After Kiribati gained independence in 1979, Europeans left the island. As a result, the present-day population of Kiritimati genetically represents the entire Gilbert Archipelago.

This is the first genome-wide genetic analysis of the inhabitants of Kiritimati Island. According to Kai Tätte, a junior researcher in population genetics at the University of Tartu and one of the study's authors, the Kiritimati population has been underrepresented in previous genetic studies. "A large-scale genetic study of Micronesian populations conducted a few years ago found that while different Micronesian populations are united by geography, they are genetically quite different due to the influence of different historical migrations. However, that study did not include Kiritimati and the Gilbert Islands, making this research highly relevant," said Tätte.

The study reveals which early and later migrations to Micronesia influenced the genetics of Kiritimati's inhabitants and which migrations they remained unaffected by. Tätte added that these findings refine previous models and provide new insights into Oceanian populations' migration routes and interconnections, improving our understanding of human movement and cultural interactions in the Pacific region.

The results show that the primary genetic ancestry of Kiritimati's inhabitants originates directly from the initial Austronesian expansion, which began in the South China and Taiwan region around 5,000 years ago. Ancient DNA analysis confirms that Kiritimati's people are direct descendants of the Lapita culture, which emerged in the Bismarck Archipelago approximately 3,500 years ago and later spread to Western Polynesia. Kiritimati inhabitants exhibit a genetic component typical of Central-Eastern Micronesian populations, indicating strong connections with Western Polynesians. Additionally, their genome contains an Australasian component characteristic of Papuans, with admixture between Austronesian and Australasian genetic material estimated between 1,440 and 2,220 years ago.

Due to the colonial era, English became the official language of Kiritimati's inhabitants, Christianity was the dominant religion, and a parliamentary system was the form of governance. "It is, therefore, fascinating that the genetic legacy of colonisation is minimal," noted Tätte, pointing out that only one out of 19 individuals in the study showed detectable Western Eurasian ancestry.

The study's findings were also shared with representatives of the Kiritimati community, who, in turn, distributed a summary of the results to local school educators and administrators.

Read the article: https://academic.oup.com/gbe/article/17/3/evaf046/8069057

Previously, Tätte has conducted two other population genetics studies on the Austronesian expansion in Southeast Asia and the Pacific:

The Ami and Yami aborigines of Taiwan and their genetic relationship to East Asian and Pacific populations

Genetic characterization of populations in the Marquesas Archipelago in the context of the Austronesian expansion