Genome study traces Hawaiʻi, Rapa Nui to Mangareva voyagers

Hawaiʻi and Rapa Nui sit about 7,000 kilometers apart, at opposite corners of the Polynesian triangle. A new genetic study finds that their peoples are each other's closest relatives among the remote island populations studied. The likely reason is that both islands were settled by voyagers whose ancestry traces back to Mangareva, in French Polynesia.today.ucsd

The study was led by researchers at the University of California San Diego and published Oct. 8 on the cover of Science. It analyzed whole-genome sequences from 1,050 people across Polynesia. The researchers found what the university calls "one of the strongest cumulative founder effects observed in human population genetics." Each new voyage carried a smaller share of the gene pool to the next island, and that pattern, the authors say, may explain why some rare disease-linked variants are common in particular island communities.science+1

A nested pattern

The paper is titled "Message in a bottleneck: Nested founder effects from French Polynesia to Rapa Nui and Hawaiʻi." It reports that Hawaiʻi and Easter Island are two of the most bottlenecked populations in Polynesia. The data came from the Austral, Society, Marquesas and Tuamotu islands and Mangareva, as well as from Rapa Nui, Native Hawaiians, Samoans and Tongans. The authors compare the result to Russian nesting dolls: each population that settled a new island holds a smaller genetic subset of the one it came from.medicalxpress+2

"As we go from one island to the next, we're selecting a subset of a gene pool, and that is shaping our genome over time," said Keolu Fox, a UC San Diego anthropologist and corresponding author.medicalxpress

The finding does not come from one method alone. A commentary in Honolulu Civil Beat describes four lines of evidence. In one of them, the team built 2,500 resampled family trees, and Hawaiʻi and Rapa Nui paired off by themselves in 61% of those trees. Mangareva filled that spot about 10% of the time. The researchers also cautioned that the genome "cannot tell you which island settled which". They describe the voyaging culture behind these settlements as Holomoana Nui, or "great ocean voyaging," and note that it involved repeated movement between islands rather than a single one-way migration.today.ucsd+1

Health implications

The team found three variants tied to recessive diseases at relatively high frequencies in French Polynesia. One, in the FAN1 gene, is linked to a rare kidney condition called karyomegalic interstitial nephritis. It appeared in more than 11% of the French Polynesian participants but is missing from gnomAD, a global genomic database of more than 800,000 people. The authors say the study does not set new clinical guidelines. They also warn that grouping all Pacific Islanders together in medical data can hide differences between island populations.medicalxpress

The research was carried out with Variant Bio, a company where Fox is a senior adviser. Variant Bio has committed 4% of its revenue and 4% of equity-derived value to the partner communities.medicalxpress

"It is remarkable to say that our achievements as voyaging people have shaped our genomes over time," Fox said.medicalxpress