Synchrotron light used to show human domestication of seeds from 2000BC

The UK's synchrotron facility, Diamond Light Source, has been used by scientists at UCL to document for the first time the rate of evolution of seed coat thinning, a major marker of crop domestication from archaeological remains. Writing in the journal Scientific Reports , the authors present evidence for seed coat thinning between 2,000 BC and 1,200 BC in the legume horsegram (Macrotyloma uniflorum), a bean commonly eaten in southern India. By using the high-resolution X-ray computed tomography (HRXCT) technique on Diamond's I13-2 beamline, the researchers were able to measure for the first time the coat thickness throughout the entire seed. 'Seed coat thickness is a great indicator of domestication, as thinner coats will mean faster germination of a seed when it is watered, but conventional methods of looking at the seed coat require breaking and destroying archaeological specimens,' explains Professor Dorian Fuller (UCL Archaeology), co-author on the paper. 'Being able to look at the seed coat thickness without breaking the sample is possible by other methods, but you can only look at a spot on the seed.The beamline at Diamond has allowed us to look at the entire seed, and has shown considerable variation within individual specimen's seed coat thickness,' adds Dr Charlene Murphy (UCL Archaeology), co-author on the paper. This is the first time that HRXCT has been applied to entire archaeological seeds, with results suggesting that previous spot measurement thickness tests could be misleading.