Integrative geochronology calibrates the Middle and Late Stone Ages of Ethiopia’s Afar Rift

The Halibee member of the Upper Dawaitoli Formation of Ethiopia’s Middle Awash study area features a wealth of Middle and Later Stone Age (MSA and LSA) paleoanthropological resources in a succession of Pleistocene sediments. We introduce these artifacts and fossils, and determine their chronostratigraphic placement via a combination of established radioisotopic methods and a recently developed dating method applied to ostrich eggshell (OES). We apply the recently developed 230Th/U burial dating of OES to bridge the temporal gap between radiocarbon (14C) and 40Ar/39Ar ages for the MSA and provide 14C ages to constrain the younger LSA archaeology and fauna to ∼24 to 21.4 ka. Paired 14C and 230Th/U burial ages of OES agree at ∼31 ka for an older LSA locality, validating the newer method, and in turn supporting its application to stratigraphically underlying MSA occurrences previously constrained only by a maximum 40Ar/39Ar age. Associated fauna, flora, and Homo sapiens fossils are thereby now fixed between 106 ± 20 ka and 96.4 ± 1.6 ka (all errors 2σ). Additional 40Ar/39 results on an underlying tuff refine its age to 158.1 ± 11.0 ka, providing a more precise minimum age for MSA lithic artifacts, fauna, and H. sapiens fossils recovered ∼9 m below it. These results demonstrate how chronological control can be obtained in tectonically active and stratigraphically complex settings to precisely calibrate crucial evidence of technological, environmental, and evolutionary changes during the African Middle and Late Pleistocene.

Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like

Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution and have been of interest since Darwin’s famous reflections on the subject. Here, we assemble a large dataset of fossil canines of the human clade, including all available Ardipithecus ramidus fossils recovered from the Middle Awash and Gona research areas in Ethiopia, and systematically examine canine dimorphism through evolutionary time. In particular, we apply a Bayesian probabilistic method that reduces bias when estimating weak and moderate levels of dimorphism. Our results show that Ar. ramidus canine dimorphism was significantly weaker than in the bonobo, the least dimorphic and behaviorally least aggressive among extant great apes. Average male-to-female size ratios of the canine in Ar. ramidus are estimated as 1.06 and 1.13 in the upper and lower canines, respectively, within modern human population ranges of variation. The slightly greater magnitude of canine size dimorphism in the lower than in the upper canines of Ar. ramidus appears to be shared with early Australopithecus, suggesting that male canine reduction was initially more advanced in the behaviorally important upper canine. The available fossil evidence suggests a drastic size reduction of the male canine prior to Ar. ramidus and the earliest known members of the human clade, with little change in canine dimorphism levels thereafter. This evolutionary pattern indicates a profound behavioral shift associated with comparatively weak levels of male aggression early in human evolution, a pattern that was subsequently shared by Australopithecus and Homo.

Effect of furrow irrigation methods and deficit irrigation levels on yield and water productivity of onion (Allium cepa L.) at Amibara, Middle Awash Valley, Ethiopia.

Background: Deficit irrigation is one of the techniques used to enhance water productivity without significant yield loss in semiarid areas. Methods: A field experiment was conducted at Werer, Middle Awash Valley during the dry season of 2017/18, 2018/19 and, 2019/20 for three consecutive years to investigate the effects of deficit irrigation levels and furrow irrigation methods on onion yield and water productivity. Split plot design with three replications, in which the irrigation methods (Conventional, Fixed and Alternate Furrow) were assigned to the main plot and the three deficit levels (100% ETc, 75% ETc and 50% ETc), were in the sub-plot. Results: Results indicate that marketable onion bulb yield and water productivity were highly affected by the interaction effect of furrow irrigation methods and irrigation levels (p < 0.05). The highest bulb yield (17580.43 kg ha-) and water productivity (11.79 kg/m3) were obtained from conventional furrow irrigation method with100% ETc and alternate furrow irrigation with 50% ETc respectively. Considering water saved and maximum yield, Onion irrigated by AFI 100% ETC resulted in a 15% yield reduction with up to 50% irrigation water saving as compared to CFI 100% ETc. Conclusion: The present study suggests that, under water limiting conditions, adopting alternate furrow irrigation with 100% ETc can be an alternative to increase water productivity without significant yield reduction.