期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：27
DOI：10.1073/pnas.2123516119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Australopithecus fossils from the richest hominin-bearing deposit (Member 4) at Sterkfontein in South Africa are considerably older than previously argued by some and are contemporary with
Australopithecus afarensis in East Africa. Our dates demonstrate the limitations of the widely accepted concept that
Australopithecus africanus, which is well represented at Sterkfontein, descended from
A. afarensis. The contemporaneity of the two species now suggests that a more complex family tree prevailed early in the human evolutionary process. The dates highlight the limitations of faunal age estimates previously relied upon for the South African sites. They further demonstrate the importance of detailed stratigraphic analysis in assessments of accurate dating of the karst cave sites in South Africa, which are stratigraphically highly complex.
Sterkfontein is the most prolific single source of
Australopithecus fossils, the vast majority of which were recovered from Member 4, a cave breccia now exposed by erosion and weathering at the landscape surface. A few other
Australopithecus fossils, including the StW 573 skeleton, come from subterranean deposits [T. C. Partridge
et al.,
Science 300, 607–612 (2003); R. J. Clarke, K. Kuman,
J. Hum. Evol. 134, 102634 (2019)]. Here, we report a cosmogenic nuclide isochron burial date of 3.41 ± 0.11 million years (My) within the lower middle part of Member 4, and simple burial dates of 3.49 ± 0.19 My in the upper middle part of Member 4 and 3.61 ± 0.09 My in Jacovec Cavern. Together with a previously published isochron burial date of 3.67 ± 0.16 My for StW 573 [D. E. Granger
et al.,
Nature 522, 85–88 (2015)], these results place nearly the entire
Australopithecus assemblage at Sterkfontein in the mid-Pliocene, contemporaneous with
Australopithecus afarensis in East Africa. Our ages for the fossil-bearing breccia in Member 4 are considerably older than the previous ages of ca. 2.1 to 2.6 My interpreted from flowstones associated with the same deposit. We show that these previously dated flowstones are stratigraphically intrusive within Member 4 and that they therefore underestimate the true age of the fossils.
