Thursday, 8 March 2012

Does starch evidence push back foxtail millet domestication?

A recent article in PNAS, by Yang Xiaoyan et al., on starch grains (and some phytoliths) from two early Holocene sites in northern China (approx. 9500-7500 BC), pushes back evidence for the early cultivation of foxtail millet. This builds on recently reported identification criteria for millet starch.  This paper is an important contribution to the earlier prehistory of grass and millet exploitation in Northern China and provides important new evidence for the discussions and debates about the timing, areas and processes of millet exploitation and initial cultivation. For on thing it highlights the importance of grasses, including a large proportion of millet grasses, in the subsistence of later hunter-gatherer, or cultivator transition, northern China. This hints at a contrast with nut-hungry and acquatic-focused south (Yangtze). These new data make foxtail millet exploitation, and possible cultivation, at least as early, if not earlier, than the claimed early Panicum from Cishan (although in the latter case, hard evidence for cultivation rather than gathering remained elusive). Phytolith data indicates the occurrence of Panicum miliaceum types only from late Donghulin. Taken with other recent finds this is suggestive that Panicum and Setaria were not brought into cultivation together, perhaps each more than once, and separately, in different parts on northern China. The bringing together of these two crops, fully domesticated, in an integrated system, would seem to be a key transition, yet to be identified, but which must have happened by the time of the emergence of the Early Yangshao tradition in the first half of the 5th Millennium BC.

The trends that Yang and colleagues have found, towards more of the larger Setaria italica like starches are suggestive a subsistence shift, and potentially as the authors argue, of changes evolving in foxtail millet, as part of the domestication process. More data from more sites and periods are needed, however, to confirm whether this a real trend. It would also be nice to see what these kinds of ratios look like on later sites with clear macro-remains of domesticated foxtail millet.

Nanzhuangtou and Donghulin as early Holocene/terminal Pleistocene transition sites with early pottery are often cited as the precursors of more typically Neolithic miller cultivators but have lacked much of any archaeobotanical evidence. These findings will take on an obvious significance to those interested in the early Holocene or early agriculture in Northern China. This study is also a good example of careful archaeological starch research, and is therefore wider methodological interest. Although starch grain research has become increasingly popular in China, some studies have been rather unconvincing, especially with regards to methodologies for identification and for being clear about uncertainties. That is not the case here, where a clear methodology for identification of millet-type starch grains has been employed which is in part qualitative and in part quantitative and it includes a clear recognition of some of the uncertainties in secure species level identifications, especially of smaller and less fissured starch grains. It is also clear that the reference collection of modern material that has been studied is the most extensive to date for Chinese grasses and this increases greatly the likelihood of their reported identifications. The inclusion of control samples of sediment and loess from Donghulin to check for contamination is also methodologically very important, since modern contamination will always be a concern in starch studies. It is also good to see consideration of the presence of immature starches, since immature millet grains are a significant component of charred assemblages, and significant present on immature/unfilled spikelets has been noted in Chinese agricultural texts throughout history, since records in the Han Dynasty. The recognition of carbonized immature Panicum grains has recently been bolstered by an experimental study blogged previously.

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