Timeline from the Cradle of Human Kind:

[beecee]

https://phys.org/news/2018-11-evolution-south-africa-hominin-fair-weather.html

Evolution: South Africa's hominin record is a fair-weather friend

November 21, 2018, University of Cape Town

New research from an international team of scientists led by University of Cape Town isotope geochemist Dr. Robyn Pickering is the first to provide a timeline for fossils from the caves within the Cradle of Humankind. It also sheds light on the climate conditions of our earliest ancestors in the area.

Published online in the journal Nature on 21 November 2018, the work corrects assumptions that the region's fossil-rich caves could never be related to each other. In fact, the research suggests fossils from Cradle caves date to just six specific time periods.

"Unlike previous dating work, which often focused on one cave, sometimes even just one chamber of the cave, we are providing direct ages for eight caves and a model to explain the age of all the fossils from the entire region," says Dr. Robyn Pickering.

"Now we can link together the findings from separate caves and create a better picture of evolutionary history in southern Africa."

Read more at: https://phys.org/news/2018-11-evolution-south-africa-hominin-fair-weather.html#jCp
 

the paper:

https://www.nature.com/articles/s41586-018-0711-0

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

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 contentious2,3,4 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.