Sunday, 5 February 2012

Millet starches: towards a systematic and quantitative approach

Yang Xiaoyan et al. have published their latest key to millet starch identification (for China) in J. of Archaeological Science "From the modern to the archaeological: starch grains frommillets and their wild relatives in China". This is an important development, partly because it is the largest comparative study yet from that part of the world (although arguably still not large enough in terms of taxa and populations!), but mainly because it provides some highly plausible and well-quantified guidelines on millet starch identification. It shows quite clearly that there is quite a lot of variation within a grain, a species and genus, the Paniceae, but also degrees of underlying similarity. The take home message is that every individual starch  is unlikely to be identifiable to the same level, to species or genus, but that some may be highly suggestive (the especially large and wrinkled examples are more common in Setaria italica than in wild Setaria or Panicum), and if on an assemblage level morphometric can be used to assess the probability of certain taxa. In other words it is the first step in building a probabilistic, rather than some qualitatively absolute, determination that the Chinese millets or there wild relative were present. Interestingly it indicates that Setaria italica is in principle far more recognizable than Panicum miliaceum, which has more 'generic' millet-grass starch. This means that rather than trying to take a small sample of few starch grains and pronounce a species presence that may not be believable, a more stasticial approach can be taken to determine a degree of likelihood. Such a quantitative apporach also open the possibility of tracking assemblages changes, which in turn might be connected to other lines of evidence for agriculture change or even plausibly put together in models about population change such as domestication processes, since Setaria viridis and Setaria italica differ in their starch grain assemblages. It also raises another potential area of investigation, which require further work, environmental conditions, since there does appear to latitude-related variation amongst  Setaria italica populations studies-- so further work is needed. The this is the best step in the right direction we have seen increasingly popular Chinese starch research world.

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