Alam, O., Gutaker, R., Wu, C., Hicks, K., Bocinsky, K., Castillo, C., Acabado, S., Fuller, D., Guedes, J., Hsing, Y., Purugganan, M. (2021). Genome analysis traces regional dispersal of rice in Taiwan and Southeast Asia. Molecular Biology and Evolution Doi.org/10.1093/molbev/msab209 Download
This recent paper by Alam et al. makes the case from genome analysis that the traditional rices cultivated by Austronesian-speaking peoples outside of Taiwan are different from those cultivated in Taiwan: they are tropical japonica rices, similar to those from mainland southeast Asia, while the majority of Taiwanese rices are temperate japonicas, close to the rices grown in north China, Korea and Japan. In their view, this goes against the “out of Taiwan” paradigm of Austronesian prehistory. Their idea is further detailed here.
The paper claims that the Taiwanese temperate japonicas were introduced from northeast China, and that the tropical japonicas in the Philippines were introduced from the south; and further, that temperate japonicas never left Taiwan. Given these very different histories, one would normally expect to see different words for temperate and tropical japonicas in the Austronesian languages. Instead, the Austronesian languages mostly use the same word for the japonica plant, whether temperate or tropical, in Taiwan or outside of Taiwan. Local phonetic variations are mostly predictable: this indicates that the words are inherited from the Austronesian ancestor language, as opposed to being borrowed locally from other Austronesian languages through contact. This term is reconstructed as *pajay in a widely-used resource . My own reconstruction is *panjay. This word is regarded by linguists as the name of the rice plant in the ancestral Austronesian language, widely believed to have been spoken before 5000 BP in Taiwan.
The formation of the Austronesian language family through a primary differentiation in Taiwan, followed by a single migration out of Taiwan circa 4000 BP, is supported by multiple lines of evidence: shared linguistic innovations of non-Formosan languages ; , Bayesian phylogenies of Austronesian languages , archaeology , studies of the Austronesian human Y-chromosome , genetics of the human pathogen Helicobacter pylori , and of the paper mulberry, a domesticated plant . Language, then, argues that the out-of-Taiwan migration did introduce temperate japonica rices, together with the term *panjay to the Philippines and islands further south. Absence of temperate japonicas in these modern regions can be explained in terms of competition between temperate and tropical japonicas: as the latter did not grow well in the new southern environment, they were out-competed by tropical japonicas introduced “from the south”— probably from mainland southeast Asia.
The higher yields of tropical japonicas would feed a larger population. This can be related to a recent proposal that Bayesian phylogenetics of Philippine languages support a diversification from the south, implying a northward back-migration of Philippine speakers . This population movement was quite plausibly fueled by the possession of tropical japonicas: it was also the instrument of their northward spread. Philippine farmers, one supposes, did not think of tropical and temperate japonicas as different plants, referring to both kinds as *panjay—they would later also recognize the more strongly divergent indica rices, introduced from the Indian subcontinent, as *panjay. When temperate japonicas were abandoned, their original name continued to be used for tropical japonicas. This both accounts for the existence of a single term for the rice plant in the Austronesian languages, and reconciles the out-of-Taiwan hypothesis with the finding of a southern origin of tropical japonicas.
The date of separation between temperate japonicas from northeast Asia and from Taiwan, given as 2600 BP by the authors, is another problematic area. They attribute the introduction of temperate japonica to Taiwan to a migration from northeast Asia, which must, then, have started after 2600 BP, and reached Taiwan at an even later date. They seek support for the migration, and for their own chronology, in the observation that “Taiwanese peoples from ~1300 BCE to 800 CE carried ~25% of a northern East Asian lineage in their genomes” . This, however, means that the northerners had already reached Taiwan by 3300 BP, 700 years before the proposed date of separation. The northerners and their temperate japonica rices may actually have reached Taiwan much earlier, as the last-mentioned study did not use any earlier ancient DNA data for Taiwan. The date the authors of that study suggest for the arrival of northerners in Taiwan is 5000-4500 BP: this is based on archaeological finds of domesticated foxtail millet in Taiwan during that period. Foxtail millet is generally thought to have been domesticated in north China around 8000 years ago. Under the Alam et al. paper, two distinct southward migrations are necessary for the introduction of millet and rice to Taiwan from northeastern China.
[Added Aug. 30, 2021: this post occasioned some reactions from authors of the Alam et al. paper. See my response here].
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