LETTER

REPLY TO BARBER: Marginal evidence for taro production in northern LETTER New Zealand between 1200 and 1500 CE Matthew Prebblea,1, Atholl J. Andersona, Paul Augustinusb, Joshua Emmittc, Stewart J. Fallond, Louise L. Fureye, Simon J. Holdawayc, Alex Jorgensenc, Thegn N. Ladefogedc,f, Peter J. Matthewsg, Jean-Yves Meyerh, Rebecca Phillippsc, Rod Wallacec, and Nicholas Porchi

We welcome Barber’s (1) comments and are grateful for not meet widely accepted criteria for high-precision the opportunity to respond. Our study of wetland taro dating, as they contain mixed carbon sources (9). (Colocasia esculenta) gardens during the initial coloni- 3) Description of crop ecosystems: Ancient crop ecosys- zation period (ICP) (1200 to 1500 CE) in New Zealand tems cannot be described without comprehensive did not overlook the evidence from the Aupouri Penin- analyses of biological remains from archaeological sula (2–4). We agree that gardens were probably estab- contexts. At Polynesian arrival, the Motutangi wet- lished on mainland New Zealand, within the climate lands were dominated by the large-statured conifer envelope shown in figure 1 of our paper (4), but in areas Dacrydium cupressinum, requiring repeated firing to that lacked large-statured forests at Polynesian arrival. establish gardens, and (3), most likely However, the fossil evidence from Motutangi does not similis, a rush which dominates the mar- meet the 3 criteria for defining ICP taro gardens met in gins of regularly flooded estuaries or lakes and out- our study of Ahuahu and subtropical French Polynesia: competes other in nutrient-poor soils (10). This densely spreading rush likely posed difficulties for 1) Reliable fossil proxies: We identify pollen, the crop cultivation, although taro may have been com- most reliable fossil proxy for taro (5), but also clus- petitive if grown in clumps over multiple sea- ters of small globular orbicular starch grains inside sons. The trees, Rhopalostylis and possible parenchyma cells, similar to those de- Cordyline, prevalent in the ICP fossil assemblages scribed by Horrocks and Barber (2). We doubt from Ahuahu, but absent from the Motutangi fossil whether these can be used to distinguish taro, records, indicate easily cleared forest with immedi- at least when using light microscopy to observe ately workable, nutrient-rich soils. We also identify starches from indigenous New Zealand species. fossil pollen and seeds of several additional plants Barber (1) in his letter does not refer to the calcium with economic value including leafy green vegeta- oxalate raphides found at Motutangi, originally at- bles (e.g., Rorippa divaricata and Sonchus kirkii), tributed to taro (2), perhaps because of a critique further indicating cultivation contexts. Furthermore, of this evidence that highlights the lack of direct ditch irrigation, reticulation, and drainage features, association between fossil proxies (6). We would similar to those described for Motutangi, were re- support a comprehensive study of starches present cently excavated on Ahuahu, at Waitetoke, with in the New Zealand flora, as has been conducted the fossil assemblages we present in our paper. for other regions (7), and further exploration of other fossil proxies for taro and other economic Finally, we agree the Little Ice Age may have induced plants (8), to improve taxonomic identification. changes in crop choices and cultivation strategies, 2) High-precision radiocarbon dates: The dates on peat perhaps linked to shifts in fire regimes and enhanced reported from Motutangi, unlike the several dates on forest clearance (11), although direct evidence for identified macrobotanical remains from Ahuahu, do such a link is lacking.

aDepartment of Archaeology and Natural History, School of Culture, History and Language, College of Asia and the Pacific, The Australian National University, Canberra, ACT 2601, Australia; bSchool of Environment, University of Auckland, Auckland 1142, New Zealand; cAnthropology, School of Social Sciences, University of Auckland, Auckland 1142, New Zealand; dResearch School of Earth Sciences, College of Physical and Mathematical Sciences, The Australian National University, Canberra, ACT 2601, Australia; eAuckland War Memorial Museum, Auckland 1142, New Zealand; fTe Punaha Matatini, Auckland 1011, New Zealand; gField Sciences Laboratory, Department of Cross-Field Research, National Museum of Ethnology, 565–8511 Osaka, Japan; hD´el ´egation à la Recherche, Gouvernement de la Polynesie ´ Française, Papeete 98713, French Polynesia; and iCentre for Integrated Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, VIC 3216, Australia Author contributions: M.P. and N.P. designed research; M.P., A.J.A., P.A., J.E., S.J.F., L.L.F., S.J.H., A.J., T.N.L., P.J.M., J.-Y.M., R.P., R.W., and N.P. performed research; M.P., R.W., and N.P. analyzed data; and M.P. wrote the paper. The authors declare no competing interest. Published under the PNAS license. 1To whom correspondence may be addressed. Email: [email protected].

www.pnas.org/cgi/doi/10.1073/pnas.1919037117 PNAS Latest Articles | 1of2 Downloaded by guest on September 30, 2021 1 I. G. Barber, Further wet-taro evidence from Polynesia’s southernmost Neolithic production margins. Proc. Natl. Acad. Sci. U.S.A. 117, 1257–1258 (2019). 2 M. Horrocks, I. Barber, Microfossils of introduced starch cultigens from an early wetland ditch in New Zealand. Arch. Oceania 40, 106–114 (2005). 3 M. Horrocks, S. L. Nichol, P. C. Augustinus, I. G. Barber, Late Quaternary environments, vegetation and agriculture in northern New Zealand. J. Quaternary Sci. 22, 267–279 (2007). 4 M. Prebble et al., Early tropical crop production in marginal subtropical and temperate Polynesia. Proc. Natl. Acad. Sci. U.S.A. 116, 8824–8833 (2019). 5 M. H. Grayum, Comparatively External Pollen Ultrastructure of the Araceae and Putatively Related Taxa (Allen Press, 1992). 6 A. Crowther, “Re-viewing raphides: Issues with the identification and interpretation of calcium oxalate crystals in microfossil assemblages” in New Directions in Archaeological Science, A. Fairbairn, S. O’Connor, B. Marwick, Eds. (ANU Press, 2009), pp. 105–118. 7 J. Mercader et al., Morphometrics of starch granules from sub-Saharan plants and the taxonomic identification of ancient starch. Front. Earth Sci. 6, 146 (2018). 8 C. Krentscher, N. Dubois, G. Camperio, M. Prebble, S. N. Ladd, Palmitone as a potential species-specific biomarker for the crop taro (Colocasia esculenta Schott) on remote Pacific islands. Org. Geochem. 132,1–10 (2019). 9 J. M. Wilmshurst, T. L. Hunt, C. P. Lipo, A. J. Anderson, High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia. Proc. Natl. Acad. Sci. U.S.A. 108, 1815–1820 (2011). 10 P. Wardle, Vegetation of New Zealand (Cambridge University Press, 1991). 11 R. Newnham, D. J. Lowe, M. Gehrels, P. Augustinus, Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change. Holocene 28, 1093–1106 (2018).

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