When I first learned of Australopithecus africanus I was very impressed with the shape of its cranium (at least of the skull specimen called "Mrs. Ples" and the skull specimen called "Taung Child"), since it strongly suggested to me that the species might have been a ancestor to our species.The skulls of that species looked much more human to me than those of Australopithecus afarensis.
Years later I learned that as a result of the discovery of Australopithecus afarensis that most anthropologists came to believe that Australopithecus africanus can not be an ancestor of ours. That greatly disappointed me and made me very sad, because it took away the joy I had in believing that Australopithecus africanus was an ancestral species of me. Two of the reasons why anthropologists abandoned Australopithecus africanus as an ancestor of our species are because: (1) Australopithecus afarensis had been dated as about one million years older than Australopithecus africanus and (2) because the molar teeth of Australopithecus afarensis were of about the same size of those of our species, whereas those Australopithecus africanus were bigger than those of ours. Because of those two factors it was thought that Australopithecus africanus evolved from Australopithecus afarensis and that our species descended from Australopithecus afarensis and some descendant species of it, but not from Australopithecus africanus.
But a very recent article (dated June 27, 2022) in a science journal states that numerous fossils of Australopithecus (including ones of Australopithecus africanus) are now re-dated as being one million years older that they previously were thought to be. The scientist who re-dated them is the same scientist who dated the fossil of Little Foot. If the new dating is correct then it means that the species Australopithecus africanus is about as old as the species Australopithecus afarensis (and older than the fossil called "Lucy") - and that Australopithecus africanus did not descend from Australopithecus afarensis (except possibly from a small early population of A. Afarensis). It also means (at least to me) that Australopithecus africanus might be an ancestral species of ours after all (and that Australopithecus afarensis might not be an ancestral species of ours). The science journal article is at https://www.pnas.org/doi/10.1073/pnas.2123516119 and is called "Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South Africa".
The science journal article says the following. "Australopithecus fossils from the richest hominin-bearing deposit
(Member 4) at Sterkfontein in South Africa are considerably older than
previously argued by some and are contemporary with Australopithecus afarensis in East Africa. Our dates demonstrate the limitations of the widely accepted concept that Australopithecus africanus, which is well represented at Sterkfontein, descended from A. afarensis.
The contemporaneity of the two species now suggests that a more complex
family tree prevailed early in the human evolutionary process."
The science journal article has a lot of technical terminology in it, but a number of news articles describe the significance of the findings in a much easier to understand manner. One of those articles is at https://www.sciencealert.com/cradle-of-humankind-fossils-may-be-a-million-years-older-than-we-previously-thought . It says the following.
'Multiple ancient hominin remains from caves in South Africa may be much, much older than previous estimates suggested.
The Sterkfontein limestone cave system, not far from Johannesburg, has yielded so many ancient bones from the hominin genus Australopithecus over
the last century that its location has been dubbed the Cradle of
Humankind – deeply important to the study of human evolution.
Now, new dating techniques suggest that the remains date back nearly 4 million years – making them even older than the famous Australopithecus afarensis individual Dinkinesh, nicknamed Lucy.
... Most of the Sterkfontein
Australopithecus remains have been
recovered from a cave infill called Member 4. That's exactly what it
sounds like: material that filled what was previously a cavity,
resulting in a sedimentary deposit; in this case, concealing but
preserving ancient hominin remains.
Member 4 previously yielded the
famous Mrs. Ples skull, the most complete example of its kind ever discovered.... the team discerned that the Australopithecus-bearing sediments
all date from between 3.4 and 3.7 million years ago. That means the
remains recovered from the deposit are all from around the beginning of
the Australopithecus era, and not its end as previously thought.
... "Younger hominins, including Paranthropus and our genus Homo, appear between about 2.8 and 2 million years ago," said archaeologist Dominic Stratford of the University of the Witwatersrand in South Africa, Sterkfontein research coordinator.
"Based on previously suggested dates, the South African Australopithecus species were too young to be their ancestors, so it has been considered more likely that Homo and Paranthropus evolved in East Africa."
The new result, consistent with the dating of Little Foot, suggests that Homo and Paranthropus
– also found in the Cradle of Humankind – emerged nearly a million
years after the Member 4 individuals lived, which means the order of
events, and where they occurred, can be revised.'
For related news articles about the findings see the following.
- https://www.newsweek.com/fossils-earliest-ancestors-million-years-older-previously-thought-scientists-1719660
- https://www.cnn.com/2022/06/28/world/sterkfontein-cave-australopithecus-fossils-age-scn/index.html . This article says that based upon the dating from decades ago that "... researchers up until now have accepted that South African Australopiths
were descended from East African species, like Lucy and other members of
Australopithecus afarensis." But the article continues by saying the following. ' “What our age shows is that this cannot be true, because they are
virtually the same age,” Granger said. “There must be an older common
ancestor. It also gives much more time for the South African species to
evolve, and reopens discussion about the role of the South African
species into later hominins such as Paranthropus.” '
- http://www.sci-news.com/archaeology/sterkfontein-australopithecus-fossils-10944.html . This article says the following.
'The team’s results show that the entire Australopithecus assemblage at Sterkfontein dates to 3.4-3.7 million years ago.
These australopiths were thus early representatives of the genus,
overlapping in age with a morphologically diverse range of mid-Pliocene
hominins, including Australopithecus afarensis and Australopithecus deyiremeda at Burtele, Australopithecus bahrelgazali in Chad, Kenyanthropus platyops at Lake Turkana, and Australopithecus anamensis at Woranso-Mille.
“The Sterkfontein hominins predate Paranthropus, Homo, and Australopithecus sediba at nearby sites in the Cradle of Humankind by over a million years,” the authors said.
In addition to the new dates at Sterkfontein based on cosmogenic
nuclides, the they made careful maps of the cave deposits and showed how
animal fossils of different ages would have been mixed together during
excavations in the 1930s and 1940s, leading to decades of confusion with
the previous ages.
“What I hope is that this convinces people that this dating method gives reliable results,” Dr. Granger said.
“Using this method, we can more accurately place ancient humans and
their relatives in the correct time periods, in Africa, and elsewhere
across the world.” '
