M.A. Theses: Nicole D. Jackman, 1999
Tef and Finger Millet: Archaeobotanical Studies of Two Indigenous East African Cereals
Distinguishing ancient domesticated cereals from wild progenitors in the archaeobotanical record has proven to be a challenge in eastern Africa. Establishing the presence of early crops at archaeological sites is fundamental in determining the antiquity of in situ cereal domestication in this region. Consequently, this study attempts to develop archaeobotanical identification criteria for two indigenous East African cereals, tef (Eragrostis tef) and finger millet (Eleusine coracana ssp. Coracana) Identification criteria are also presented for the wild progenitors of these cereals including Eragrostis pilosa, Eleusine coracana ssp. Africana, as well as Eleusine indica.
The study employs several analytical methods. Modern reference specimens and light microscopy are used to make morphological comparisons between domesticated and wild species of tef and finger millet grains. Specimens from all five taxa were experimentally charred, and changes in caryopsis morphology were quantified to establish the affects on grain characters. Scanning electron microscopy (SEM) was employed to identify and illustrate the microtopography and morphology of grains and chaff elements not visible using regular light microscopy. Lastly, identification criteria were applied to a sample of archaeological Eragrostis grains from Ona Nagast, near Aksum in Ethiopia, to determine their effectiveness for classifying ancient domesticated tef grains.
The results show that tef is difficult to identify from its wild progenitor, Eragrostis pilosa using caryopsis morphology. Caryopsis length, breadth, thickness, and embryo length are reliable criteria for separating the two taxa when more than one of these measurements is used. Hilum dimensions and embryo breadth may further strengthen identifications where available. Charring appears to slightly reduce overlap in the measurement ranges of E. tef, E. pilosa, E. coracana ssp, africana and E. indica. Metrical criteria applied to a sample of archaeological Eragrostis grains from Ona Nagast were effective in differentiating specimens as E. tef, c.f.E tef or Eragrostis sp. Finger millet (Eleusine coracana ssp. Coracana) is easily separated from its wild progenitor E. coracana ssp. africana using caryopsis and bracteole morphology. E. coracana ssp. africana and a related weed species, E. indica, are morphologically similar but can be differentiated using caryopsis shape and dimensions. There was considerable variation in grain shape and seed coast pattern within domesticated finger millet. This variability was illustrated using metrical data and SEM.