New dates for South African fossils cause contention
Recently Granger et al. published new dates for the Sterkfontein Australopithecus fossils from South Africa. They used a method known as Cosmogenic Nuclide Burial Dating. This technique had earlier been used to date the Australopithecus Little Foot skeleton to allegedly 3.7 Ma (million years ago). This date, along with the new dates for the other Australopithecus fossils (including Australopithecus africanus), yielded a combined range of supposedly 3.4 to 3.7 Ma for the Australopithecus assemblage. This was about a million years older than the previous ages attributed to these fossils.
The new age range overlaps with Australopithecus afarensis fossils (e.g., Lucy) from East Africa, alleged to be the ancestor of the human lineage. The Sterkfontein Australopithecus assemblage now competes with Australopithecus afarensis as ancestors of later supposed hominins, including the genus Homo.
On how to resolve disagreements between different research teams on the ages of the Sterkfontein fossils, Charles Choi writes (quoting paleoanthropologist John Hawks):
“For example, scientists who want to solve the puzzle of the ages of these bones may take part in double-blind experiments involving ‘different groups of researchers examining the same samples, without knowing where they are from until they report their results,’ Hawks said. ‘Otherwise, there is too much potential for researchers to choose samples and methods that reinforce their own ideas.’”
One wonders how many alleged ages reported in the literature were selected because they reinforced the ideas of the researchers. Redating of fossils is not a rare occurrence. The new dates discussed above illustrate the fickle nature of age estimates obtained from dating methods.
- Choi, C.Q., South African fossils may rewrite history of human evolution, livescience.com, 3 Jul 2022.
- Granger, D.E. et al., Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South Africa, PNAS 119(27):e2123516119, 27 Jun 2022.
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