Genetic Ancestry of Rapanui before and after European Contact

Abstract

The origins and lifeways of the inhabitants of Rapa Nui (Easter Island), a remote island in the southeast Pacific Ocean, have been debated for generations. Archaeological evidence substantiates the widely accepted view that the island was first settled by people of Polynesian origin, as late as 1200 CE [1-4]. What remains controversial, however, is the nature of events in the island's population history prior to the first historic contact with Europeans in 1722 CE. Purported contact between Rapa Nui and South America is particularly contentious, and recent studies have reported genetic evidence for Native American admixture in present-day indigenous inhabitants of Rapa Nui [5-8]. Statistical modeling has suggested that this genetic contribution might have occurred prior to European contact [6]. Here we directly test the hypothesis that the Native American admixture of the current Rapa Nui population predates the arrival of Europeans with a paleogenomic analysis of five individual samples excavated from Ahu Nau Nau, Anakena, dating to pre- and post-European contact, respectively. Complete mitochondrial genomes and low-coverage autosomal genomes show that the analyzed individuals fall within the genetic diversity of present-day and ancient Polynesians, and we can reject the hypothesis that any of these individuals had substantial Native American ancestry. Our data thus suggest that the Native American ancestry in contemporary Easter Islanders was not present on the island prior to European contact and may thus be due to events in more recent history.

Reconstructing the history of founder events using genome-wide patterns of allele sharing across individuals

“…We inferred the founder event occurred ~200–500 years ago ( Fig 2 ), postdating the European colonization of the Americas [ 39 ]. The strongest founder event was documented in Rapa Nui that occurred ~260 years ago, coinciding with the migration of Europeans to the island [ 40 ].…”

Human Discovery and Settlement of the Remote Easter Island (SE Pacific)

“…A more recent study analyzed the DNA of five skeletons from an archaeological site on the Anakena beach dated to 1445-1624 CE (pre-European contact) to 1815-1945 CE (post-European contact) [55]. No American ancestry was found for any of them and the authors suggested that contemporary American ancestry found in previous studies [53,54] was not present in the island prior to European contact and may be due to contacts in more recent history.…”

A mass sacrifice of children and camelids at the Huanchaquito-Las Llamas site, Moche Valley, Peru

“…We build double-stranded, partially UDG treated sequencing libraries [61] from the DNA extracts, and sequenced those for ~300,000 reads on a Illumina MiSeq Next Generation Sequencer (NGS) (see Table 3– NGS sequencing statistics). After demultiplexing, resulting sequencing reads were processed using the in-house computational pipeline developed for aDNA described in (Fehren-Schmitz et al [62], which includes the assessment of DNA damage patterns and mitochondrial contamination rations [63–64]. We confirmed the Native American ancestry of the individuals by determining their mitochondrial haplogroups (Tables 2 and 3) using a multiplex single-base extension PCR assay [65].…”