Revised age estimates of Australopithecus‐bearing deposits at Sterkfontein, South Africa

Abstract

The Sterkfontein fossil site in South Africa has produced the largest concentration of early hominin fossils from a single locality. Recent reports suggest that Australopithecus from this site is found within a broad paleontological age of between 2.5-3.5 Ma (Partridge [2000] The Cenozoic of Southern Africa, Oxford: Oxford Monographs, p. 100-125; Partridge et al. [2000a], The Cenozoic of Southern Africa, Oxford: Oxford Monographs, p. 129-130; Kuman and Clarke [2000] J Hum Evol 38:827-847). Specifically, the hominin fossil commonly referred to as the "Little Foot" skeleton from Member 2, which is arguably the most complete early hominin skeleton yet discovered, has been magnetostratigraphically dated to 3.30-3.33 Ma (Partridge [2000] The Cenozoic of Southern Africa, Oxford: Oxford Monographs, p. 100-125; Partridge et al. [2000a], The Cenozoic of Southern Africa, Oxford: Oxford Monographs, p. 129-130). More recent claims suggest that hominin fossils from the Jacovec Cavern are even older, being dated to approximately 3.5 Ma. Our interpretation of the fauna, the archeometric results, and the magnetostratigraphy of Sterkfontein indicate that it is unlikely that any Members yet described from Sterkfontein are in excess of 3.04 Ma in age. We estimate that Member 2, including the Little Foot skeleton, is younger than 3.0 Ma, and that Member 4, previously dated to between 2.4-2.8 Ma, is more likely to fall between 1.5-2.5 Ma. Our results suggest that Australopithecus africanus should not be considered as a temporal contemporary of Australopithecus afarensis, Australopithecus bahrelghazali, and Kenyanthropus platyops.

The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa

“…This problem is well illustrated with the on-going debate on the age of Stw 573 (‘little foot’) in the nearby Sterkfontein Cave, where after 20 years of dating efforts no definitive age is yet established (see Partridge et al, 1999, 2003; Berger et al, 2002; Walker et al, 2006; Herries and Shaw, 2011; Pickering and Kramers, 2010; Granger et al, 2015; Kramers and Dirks, 2017). Another good example illustrating the difficulties of linking cave stratigraphy to a definitive age for the hominin fossils they contain is presented by the H. floresiensis remains in the Liang Bua cave, Indonesia (Morwood et al, 2004; Roberts et al, 2009; Sutikna et al, 2016).…”

“…In the absence of volcanic deposits, it is generally difficult to obtain accurate ages for the fossils, not just because reliable techniques are few, but mostly because the stratigraphic sequences in the caves are complex, discontinuous and frequently reworked (e.g., Brain, 1993; Pickering et al, 2011a; Bruxelles et al, 2014; Stratford et al, 2014). Workers have relied on a combination of biochronology of faunal remains, palaeomagnetic work and a range of radiometric methods, including U-Pb, U-Th and ESR dating targeting flowstones and fossil teeth (e.g., Vrba, 1975; Partridge et al, 1999; Berger et al, 2002; Walker et al, 2006; Herries et al, 2006, 2013, 2014; Herries and Shaw, 2011; Dirks et al, 2010; Pickering and Kramers, 2010; Pickering et al, 2011a; Herries and Adams, 2013), as well as limited cosmogenic ( 10 Be, 16 Al) dating (e.g., Partridge et al, 2003; Granger et al, 2015; Dirks et al, 2016b). Whilst some of these techniques are well established, others such as the application of cosmogenic isochrons (e.g., Granger et al, 2015) are relatively new and not without significant analytical (and interpretative) challenges (Kramers and Dirks, 2017), and all efforts are strongly dependent on the stratigraphic interpretation of the fossils or units that are being dated.…”

The carbon isotope ecology and diet of Australopithecus africanus at Sterkfontein, South Africa

“…Member 4 has been variously estimated by different authors (e.g., Johanson and Edey, 1981;Partridge and Watt, 1991;Partridge et al, 2002a,b;Kuman and Clarke, 2000) to date between 3 and 2 Ma. A recent debate about the chronology (Berger et al, 2002;Clarke, 2002a;Partridge, 2002) demonstrates that the issue remains unsettled; dates between 2.5 and 2.0 Ma are probably reasonable estimates for our purpose. It is well beyond the scope of our study to comment on the chronology of the hominins at Sterkfontein.…”

Geological Setting and Age of Australopithecus sediba from Southern Africa

“…Formal theoretical analyses [e.g., (2, 5-9, 11-13, 19)] and experimental studies (20,21) have explored a small number of plausible learning strategies. Although insightful, this work has focused on simple rules that can be studied with analytical methods and can only explore a tiny subset of strategies.…”