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Nature. 2019 Aug;572(7767):112-115. doi: 10.1038/s41586-019-1370-5. Epub 2019 Jul 15.

Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress.

Author information

1
Geoarchaeology and Archaeometry Research Group, Southern Cross GeoScience, Southern Cross University, Lismore, New South Wales, Australia. renaud.joannes-boyau@scu.edu.au.
2
Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia.
3
Palaeo-Research Institute, University of Johannesburg, Johannesburg, South Africa.
4
Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
5
Archaeology, College of Humanities, Arts and Social Sciences, Flinders University, Adelaide, South Australia, Australia.
6
McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK.
7
Palaeoscience Laboratory, Department of Archaeology and History, La Trobe University, Melbourne, Victoria, Australia.
8
Geoarchaeology and Archaeometry Research Group, Southern Cross GeoScience, Southern Cross University, Lismore, New South Wales, Australia.
9
Department of Cultural Heritage, University of Bologna, Ravenna, Italy.
10
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
11
School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.
12
Geosciences, Museums Victoria, Melbourne, Victoria, Australia.
13
Department of Paleoanthropology, Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt, Germany.
14
Department of Paleobiology and Environment, Institute of Ecology, Evolution, and Diversity, Johann Wolfgang Goethe University, Frankfurt, Germany.
15
Function, Evolution and Anatomy Research Laboratory, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
16
Wollongong Isotope Geochronology Laboratory, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, New South Wales, Australia.
17
Earth Sciences, University of New England, Armidale, New South Wales, Australia.

Abstract

Reconstructing the detailed dietary behaviour of extinct hominins is challenging1-particularly for a species such as Australopithecus africanus, which has a highly variable dental morphology that suggests a broad diet2,3. The dietary responses of extinct hominins to seasonal fluctuations in food availability are poorly understood, and nursing behaviours even less so; most of the direct information currently available has been obtained from high-resolution trace-element geochemical analysis of Homo sapiens (both modern and fossil), Homo neanderthalensis4 and living apes5. Here we apply high-resolution trace-element analysis to two A. africanus specimens from Sterkfontein Member 4 (South Africa), dated to 2.6-2.1 million years ago. Elemental signals indicate that A. africanus infants predominantly consumed breast milk for the first year after birth. A cyclical elemental pattern observed following the nursing sequence-comparable to the seasonal dietary signal that is seen in contemporary wild primates and other mammals-indicates irregular food availability. These results are supported by isotopic evidence for a geographical range that was dominated by nutritionally depauperate areas. Cyclical accumulation of lithium in A. africanus teeth also corroborates the idea that their range was characterized by fluctuating resources, and that they possessed physiological adaptations to this instability. This study provides insights into the dietary cycles and ecological behaviours of A. africanus in response to food availability, including the potential cyclical resurgence of milk intake during times of nutritional challenge (as observed in modern wild orangutans5). The geochemical findings for these teeth reinforce the unique place of A. africanus in the fossil record, and indicate dietary stress in specimens that date to shortly before the extinction of Australopithecus in South Africa about two million years ago.

PMID:
31308534
DOI:
10.1038/s41586-019-1370-5

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