News & views observations of weather during the first Smyth (eds Duffy, P. J. & Nolan, W.) Ch. 5 (Geography Poly nesian DNA markers with those of people seven centuries bc, and which remain largely Publs, 2012). from other regions, including Europe, Amer- 7 4. Freeman, A. M. (ed.) Annála Connacht: The Annals of unexploited. As Pfister and Wanner stated in Connacht, A.D. 1224–1544 (Dublin Inst. Advanced Studies, ica, Africa and Melanesia. A computational 2002, “Worldwide, many thousand volumes 1944). method called an ADMIXTURE analysis with daily observations exist, but have not yet 5. Brooks, C. E. P. Q. J. R. Meteorol. Soc. 54, 309–317 (1928). allowed Ioannidis and colleagues to work out a 6. Chambers, F. M. & Brain, S. A. Holocene 12, 239–249 been analyzed for their climatic information. (2002). person’s probable genetic ancestry and ances- Let’s get to work!” 7. Pfister, C. & Wanner, H. Past Glob. Changes Mag. 10, 2 tral geographical origins through studies of (2002). gene flow. Their main discovery is that several 8. Brázdil, R., Pfister, C., Wanner, H., Von Storch, H. & Francis Ludlow and Rhonda McGovern Luterbacher, J. Clim. Change 70, 363–430 (2005). eastern Polynesian populations have signs of are at the Trinity Centre for Environmental 9. White, S., Pfister, C. & Mauelshagen, F. (eds) The Palgrave a background signature (genetic traces from Humanities, School of Histories and Handbook of Climate History (Palgrave Macmillan, 2018). distant ancestors) that originated from Native 10. Camenisch, C., Bauch, M., Huhtamaa, H., Pei, Q. & Humanities, Trinity College, Dublin D02 PN40, White, S. Past Glob. Changes Mag. 27, 73 (2019). South American people. Ireland. 11. Blöschl, G. et al. Nature 573, 108–111 (2019). How did Ioannidis and colleagues solve this 12. Gao, C., Ludlow, F., Amir, O. & Kostick, C. Quat. Int. 394, e-mail: [email protected] 180–193 (2016). complex task of genetic unravelling? In their 13. Pfister, C. et al. Clim. Change 131, 191–198 (2015). admixture studies, they could trace and dis- 1. Blöschl, G. et al. Nature 583, 560–566 (2020). 14. Huijs, J., Pirngruber, R. & van Leeuwen, B. in A History tinguish between different modern colonial 2. Paprotny, D., Sebastian, A., Morales-Nápoles, O. & of Market Performance: From Ancient Babylonia to the Jonkman, S. N. Nature Commun. 9, 1985 (2018). Modern World (eds van der Spek, R. J., van Leeuwen, B. & admixtures; for example, in French Polynesia, 3. Ludlow, F. in At the Anvil: Essays in Honour of William J. van Zanden, J. L.) 128–148 (Routledge, 2015). there was a large French influence, whereas Spanish and Chilean groups were part of the population history in Rapa Nui. A key discovery Human migration came from their analysis of people from Rapa Nui — a signature could be assigned to Native Native South Americans South American populations from northern coastal regions of South America, and this component was independent of other large reached Polynesia early historical, or more-recent, admixture events. This signature exists in the genetic back- ground, indicating that it is an old and stable Paul Wallin hallmark of admixture. A surprising finding DNA analysis of Polynesians and Native South Americans is that this signal was also identified in other has revealed an ancient genetic signature that resolves a eastern Polynesian populations, for example long-running debate over Polynesian origins and early contacts in populations in Mangareva, in North Marque- sas and South Marquesas, and in Palliser in the between the two populations. See p.572 Tuamotu Islands (Fig. 1). These other islands lie farther from South America than does Rapa Nui, although for people sailing from South For many years, scholars have speculated best-known example considered concerning America they are destinations that would be about how Polynesia was initially populated. such contacts4. It is a part of Polynesia that aided by favourable trade winds and currents. On page 572, Ioannidis et al.1 now describe a is located relatively close to South America, Ioannidis et al. investigated the estimated genetic approach that they used to address the and in Rapa Nui there is evidence of large, timing of admixture events using a method issue of Polynesian origins and inter actions. ancient sweet-potato fields, extraordinary called tract-length distribution analysis, The early peopling of Polynesia attracted old stonework and a specific birdman cult — which assesses the length distributions of worldwide interest in 1947, when the all of which are features in common with those the genomic segments inherited from differ- Norwegian explorer Thor Heyerdahl set sail of South America. ent ancestral populations. As expected, this on the Kon-Tiki expedition to test his migration Ioannidis and colleagues analysed the DNA statistical approach suggests that the Euro- theory2. The crew left Peru on a wooden raft, pean admixtures in Polynesia first date back and after 101 days and a voyage of more than “Future research should to colonial phases of ad 1750–1860. 7,000 kilometres, they reached Polynesian The authors made the notable discovery shores, thus demonstrating the possibility assess the possibility of more that an initial admixture event between of early travel from South America to these than just one early contact Native South Americans and Polynesians took Pacific islands. Heyerdahl challenged the from South America.” place in eastern islands of Polynesia around scientific community’s view that evidence ad 1150–1230. Previous work3,5 is consistent pointed instead to the peopling of Polynesia by with a model of populations spreading east- people travelling east from Asia, and his idea of people from Rapa Nui, and also studied wards from Asia possibly having reached that Polynesia was initially populated by South DNA of individuals from 17 populations of eastern Polynesia by that time. The exception Americans was generally criticized by scholars. Pacific islands and 15 Native American popu- to this South American admixture timeframe The same scientific community nevertheless lations from the Pacific coast of South Amer- is Rapa Nui, which had a later admixture, dated discussed cultural contacts between the two ica. Genome-wide DNA analyses of 807 people to around ad 1380. This later date for Rapa Nui regions, because a South American plant, the (analysing predominantly present-day indi- is surprising, because it is the closest site to sweet potato, has a long history of cultivation viduals) enabled the authors to search for evi- South America studied and has been cited as in eastern Polynesia. The idea that Polynesians dence of ancestors from different populations the ‘typical’ example of a location with possible voyaged to South America and introduced who produced offspring together — thereby early connections to South America. However, the plant on their return to Polynesia generating a combined genetic signature of the timing difference might be due to a more became the accepted explanation for this3. the two populations, described as an admix- complex genetic history there because of Rapa Nui (also known as Easter Island) is the ture. The authors compared the dominant relatively recent Chilean genetic input. 524 | Nature | Vol 583 | 23 July 2020 ©2020 Spri nger Nature Li mited. All rights reserved. ©2020 Spri nger Nature Li mited. All rights reserved. When Ioannidis and colleagues searched for similarities between the genetic signatures of Native South Americans found in Polynesia South Pacific Ocean Marquesas and those of Indigenous populations in North admixture COLOMBIA northern coastal areas of South America, the Marquesas by AD 1150 Migration from connection to Colombian populations was Migration from Asia admixture to western Polynesia by AD 1200 Colombia especially strong. The earliest genetic signal (1500–800 BC) PERU of Native Southern Americans found by the authors in Polynesia was from people of the Migration to Palliser Rapa Nui Southern Marquesas islands, and the authors eastern Polynesia admixture (Easter Island) argue that Colombians mixed with Polynesians AUSTRALIA (by ~ AD 1025) by AD 1230 admixture there around ad 1150. This date is so early Mangareva by AD 1380 that it could even suggest South Americans admixture by AD 1230 reached there before Polynesians arrived, NEW ZEALAND which would make Heyerdahl partly right if it were the case that South Americans first settled at least the area of eastern Polynesia Figure 1 | Genetic clues reveal early migration from South America to Polynesia. Ioannidis et al.1 report that has signs of early admixture. a DNA analysis of Polynesians and Native American people from South America, focused mainly on modern The authors propose that the Native populations. The authors shed light on the early peopling of Polynesia by uncovering signs of ancient South American genetic signatures they encounters between Polynesians and South Americans (probably those from Colombia), which resulted in found were probably the result of a single a genetic signature called an admixture indicating that children had parents from both populations. The ancient contact. Their model suggests that earliest signs of such admixture in Polynesia were estimated to have occurred on the Southern Marquesas islands in ad 1150. Previous studies3,5 indicate that populations moving eastwards from Asia had populated the mixed population then spread from this area by around that time. The authors find evidence for the same type of population admixture being central eastern Polynesia around ad 1200 present between ad 1150 and ad 1230 in nearby islands, and then in Rapa Nui (also known as Easter Island) to other Poly nesian islands during an early by ad 1380. Some Polynesian islands, including Rapa Nui, have characteristics in common with those of eastern Polynesian expansion, and finally ancient South America, such as elaborate stonework and the sweet-potato plant. But an early role for South reached Rapa Nui. These spectacular results Americans in the peopling of the Polynesian islands had not previously been widely accepted.