Oryza sativa dating from 12,000–11,000 BP indicates that wild rice collection was part of the local means of subsistence. Changes in the morphology of Diaotonghuan phytoliths dating from 10,000–8,000 BP show that rice had by this time been domesticated. Analysis of Chinese rice residues from Pengtoushan, which were carbon 14 dated to 8200–7800 BC, show that rice had been domesticated by this time. In 1998, Crawford and Shen reported the earliest of 14 AMS or radiocarbon dates on rice from at least nine Early to Middle Neolithic sites are no older than 7000 BC, that rice from the Hemudu and Luojiajiao sites
Helitron (biology) Helitron (biology) Helitrons are one of the three groups of eukaryotic class 2 transposable elements (TEs) so far described. They are the eukaryotic rolling-circle transposable elements which are hypothesized to transpose by a rolling circle replication mechanism via a single-stranded DNA intermediate. They were first discovered in plants ("Arabidopsis thaliana" and "Oryza sativa") and in the nematode "Caenorhabditis elegans", and now they have been identified in a diverse range of species, from protists to mammals. Helitrons make up a substantial fraction of many genomes where non-autonomous elements frequently outnumber the putative autonomous partner. Helitrons seem to have a major role