New age constraints for the Singa hominin and the adjacent Abu Hugar fossil site

The Singa calvaria, found on the western bank of the Blue Nile in Sudan in 1924, shows a combination of modern and archaic features of Homo sapiens . A previous study applying U-Th dating of calcrete precipitates surrounding the calvaria and associated mammal teeth inferred a minimum age of 133 ± 2 ka. However, detailed age constraints on the Singa calvaria are still lacking. The Abu Hugar site, located just 35 km to the south of Singa, produced vertebrate fossils and stone artifacts previously thought to be contemporaneous with the calvaria. Here, we applied optically stimulated luminescence (OSL) dating on the fluvial sediments and radiocarbon dating on soils and shells from Singa and Abu Hugar. Small aliquots for quartz and single grains for K-feldspar were used in luminescence dating to address possible partial bleaching issue. Using a Bayesian age-depth model and assuming continuous deposition, we estimate a considerably younger burial age of 39 ± 4 ka for the Singa calvaria. Though we cannot rule out an older age, our new age estimate suggests that the Singa hominin might significantly postdate the origin of anatomically modern humans and the dispersal of Homo sapiens out of Africa. In contrast, the fluvial sediments from Abu Hugar have much older OSL ages of ∼120–210 ka for the exposed profile with the oldest fossiliferous level possibly as old as ∼315 ka. Our dating results challenge the previously assumed contemporaneity of the Singa calvaria and the faunal and lithic records of Abu Hugar, and reflect a complex Pleistocene history of Blue Nile deposition. • Luminescence dating is performed at Singa and Abu Hugar fossil sites • Singa calvaria might be as young as 39 ± 4 ka • Abu Hugar sediments have luminescence ages of ∼120–210 ka • Presumed temporal connection between Singa and Abu Hugar is challenged