U–Pb-dated flowstones restrict South African early hominin record to dry climate phases

Robyn Pickering (), Andy I. R. Herries, Jon D. Woodhead, John C. Hellstrom, Helen E. Green, Bence Paul, Terrence Ritzman, David S. Strait, Benjamin J. Schoville and Phillip J. Hancox
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Robyn Pickering: University of Cape Town
Andy I. R. Herries: La Trobe University
Jon D. Woodhead: The University of Melbourne, Melbourne
John C. Hellstrom: The University of Melbourne, Melbourne
Helen E. Green: The University of Melbourne, Melbourne
Bence Paul: The University of Melbourne, Melbourne
Terrence Ritzman: University of Cape Town
David S. Strait: Washington University in St. Louis
Benjamin J. Schoville: University of Cape Town
Phillip J. Hancox: University of the Witwatersrand

Nature, 2019, vol. 565, issue 7738, 226-229

Abstract: Abstract The Cradle of Humankind (Cradle) in South Africa preserves a rich collection of fossil hominins representing Australopithecus, Paranthropus and Homo1. The ages of these fossils are contentious2–4 and have compromised the degree to which the South African hominin record can be used to test hypotheses of human evolution. However, uranium–lead (U–Pb) analyses of horizontally bedded layers of calcium carbonate (flowstone) provide a potential opportunity to obtain a robust chronology5. Flowstones are ubiquitous cave features and provide a palaeoclimatic context, because they grow only during phases of increased effective precipitation6,7, ideally in closed caves. Here we show that flowstones from eight Cradle caves date to six narrow time intervals between 3.2 and 1.3 million years ago. We use a kernel density estimate to combine 29 U–Pb ages into a single record of flowstone growth intervals. We interpret these as major wet phases, when an increased water supply, more extensive vegetation cover and at least partially closed caves allowed for undisturbed, semi-continuous growth of the flowstones. The intervening times represent substantially drier phases, during which fossils of hominins and other fossils accumulated in open caves. Fossil preservation, restricted to drier intervals, thus biases the view of hominin evolutionary history and behaviour, and places the hominins in a community of comparatively dry-adapted fauna. Although the periods of cave closure leave temporal gaps in the South African fossil record, the flowstones themselves provide valuable insights into both local and pan-African climate variability.

Keywords: Flowstone; Hominin Fossil Record; Open Caves; Shuttle Radar Topography Mission Dataset; Malapa (search for similar items in EconPapers)
Date: 2019
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DOI: 10.1038/s41586-018-0711-0

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