posted on 2025-03-26, 03:01authored byRenaud Joannes-Boyau, Justin W Adams, Christine Austin, Manish Arora, Ian Moffat, Andrew HerriesAndrew Herries, Matthew P Tonge, Stefano Benazzi, Alistair R Evans, Ottmar Kullmer, Stephen Wroe, Anthony Dosseto, Luca Fiorenza
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.
Funding
Part of this study was funded by Monash University seed grant to L.F., J.W.A., A.R.E., A.I.R.H., S.W., S.B., O.K. and R.J.-B. A.I.R.H., J.W.A. and R.J.-B. received funding from the Australian Research Council Discovery Grant DP170100056. C.A. is supported by NICHD award R00HD087523. I.M. is supported by an Australian Research Council DECRA Fellowship (DE160100703), a Commonwealth Rutherford Fellowship from the Commonwealth Scholarship Commission and a Research Associate position from Homerton College. M.A. is supported by the US National Institutes of Environmental Health Sciences Grants U2CES026561 and DP2ES025453.