Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South
Africa

Abstract

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.

https://www.pnas.org/doi/full/10.1073/pnas.2123516119

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Op dinsdag 28 juni 2022 om 17:09:04 UTC+2 schreef Pandora:

Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South
Africa

:-) Yes, thanks, this beautifully confirms my view that E & S.Afr.apiths evolved in parallel from Pliocene "gracile" afarensis//africanus to early-Pleistocene "robust" boisei//robustus.
Google "Verhaegen Human Evolution".
Lost likely, gracile apiths were bipedally wading + climbing arms overhead in swamp forests, not unlike google "bonobo wading" illustrations.
Early-Pleistocene robusts were perhaps more wading for sedges, waterlilies etc., and less climbing?
Needless to say, apiths were no human ancestors, of course, as anthropocentrically believed by traditional paleo-anthropologists, but were fossil relatives of Pan (S.Africa) & Gorilla (E.Africa).

Schematically:
-Pliocene aquarboreal graciles,
-early-Pleistocene bipedally wading robusts,
-late-Pleistocene knuckle-walking apes,
or
Gorilla//Pan
-afarensis//africanus,
-boisei//robustus,
-gorilla//troglodytes.

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.

https://www.pnas.org/doi/full/10.1073/pnas.2123516119

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