Wednesday, 8 February 2012

The rapid spread & differentiation of maize: new Peruvian data

New finds from the N. Peruvian coast report clear evidence for an earlier arrival of maize the region than previously thought (Grobman & al., PNAS), and with wonderful dessicated preservation indicating that they are popcorn varieties, but flourly varieties are also present. That there is a popcorn indicates quite rapid early varietal diversification, and these show already traits of South American rather Mesoamerican varieties. A direct AMS date puts these back to at least 4500 BC, so still a few millennia after perhaps 7000 BC date for the earliest maize in its Mesoamerican place of origin. The macro-remains are augmented by phytolith analyses and strach grains extracted both from the maize cobs and tools. Of methodological interest is the apparent discrepancy between dates on dessicated and dates on carbonized material, with the dessicated stuff being way to young. This may mean the dried stuff may sometime get contaminated with young carbon in some way (whereas the charred stuff has it true carbon fixed nicely by carbonization). Also of note is that maize is apparently not the most common plant find, and was not the dietary staple, although the present PNAS article focuses on the details of maize and we will have to await another forthcoming publication in Antiqiuty for more on the chillis, beans, squash and wild plants. Another discussion of this paper can be found in ScienceDaily news report from a couple of weeks ago.

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