Granger specializes in dating geologic deposits, including those in caves. His previous work at Sterkfontein dated the Little Foot skeleton to about 3.7 million years old, however scientists are still disputing the age of other fossils at the site.
Darryl Granger of Purdue University established the technology that upgraded the age of an Australopithecus found in Sterkfontein Cave. New information pushes its age back more than a million years, to 3.67 million years old. Credit: Purdue University photo/Lena Kovalenko
In a brand-new study released on June 27, 2022, in the Proceedings of the National Academy of Sciences, Granger and a group of researchers including scientists from the University of the Witwatersrand in Johannesburg, South Africa and the University Toulouse Jean Jaurès in France, have found that not only Little Foot, but all of the Australopithecus-bearing cavern sediments date from about 3.4 to 3.7 million years old, rather than 2-2.5 million years old as researchers formerly thought. That age puts these fossils toward the start of the Australopithecus period, rather than near completion. Dinkinesh, who hails from Ethiopia, is 3.2 million years of ages, and her species, Australopithecus africanus, hails back to about 3.9 million years of ages.
Sterkfontein is a deep and intricate cavern system that preserves a long history of hominin profession of the location. Comprehending the dates of the fossils here can be tricky, as rocks and bones tumbled to the bottom of a deep hole in the ground, and there are couple of ways to date cave sediments..
In East Africa, where numerous hominin fossils have actually been discovered, the Great Rift Valley volcanoes put down layers of ash that can be dated. Scientists use those layers to approximate how old a fossil is. In South Africa– especially in a cave– the scientists dont have that luxury. They usually utilize other animal fossils discovered around the bones to approximate their age or calcite flowstone deposited in the cave. Bones can move in the cave, and young flowstone can be deposited in old sediment, making those techniques potentially incorrect. A more precise technique is to date the actual rocks in which the fossils were found. The concrete-like matrix that embeds the fossil, called breccia, is the product Granger and his team evaluated.
” Sterkfontein has more Australopithecus fossils than anywhere else in the world,” Granger said. Individuals have looked at the animal fossils found near them and compared the ages of cavern functions like flowstones and gotten a variety of various dates.
Granger and the group utilized accelerator mass spectrometry to measure radioactive nuclides in the rocks, in addition to geologic mapping and an intimate understanding of how cavern sediments build up to figure out the age of the Australopithecus-bearing sediments at Sterkfontein.
Granger and the research group at the Purdue Rare Isotope Measurement Laboratory (PRIME Lab) study so-called cosmogenic nuclides and what they can expose about the history of fossils, geological features and rock. Because aluminum-26 is formed when a rock is exposed at the surface, but not after it has actually been deeply buried in a cave, PRIME laboratory scientists can date cavern sediments (and the fossils within them) by measuring levels of aluminum-26 in tandem with another cosmogenic nuclide, beryllium-10.
In addition to the new dates at Sterkfontein based on cosmogenic nuclides, the research team made careful maps of the cavern deposits and revealed how animal fossils of various ages would have been blended together during excavations in the 1930s and 1940s, leading to years of confusion with the previous ages. “What I hope is that this convinces individuals that this dating method gives reliable results,” Granger said. “Using this technique, we can more properly place ancient humans and their loved ones in the right time durations, in Africa, and elsewhere throughout the world.”.
The age of the fossils matters since it affects researchers understanding of the living landscape of the time. How and where human beings evolved, how they suit the ecosystem, and who their closest family members are and were, are pushing and complicated questions. Putting the fossils at Sterkfontein into their correct context is one action towards solving the entire puzzle.
Recommendation: “Cosmogenic nuclide dating of Australopithecus at Sterkfontein, South Africa” by Darryl E. Granger, Dominic Stratford, Laurent Bruxelles, Ryan J. Gibbon, Ronald J. Clarke and Kathleen Kuman, 27 June 2022, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2123516119.
Sterkfontein is the most prolific single source of Australopithecus fossils, the huge majority of which were recuperated from Member 4, a cave breccia now exposed by disintegration and weathering at the landscape surface. Here, we report a cosmogenic nuclide isochron burial date of 3.41 ± 0.11 million years (My) within the lower middle part of Member 4, and simple burial dates of 3.49 ± 0.19 My in the upper middle part of Member 4 and 3.61 ± 0.09 My in Jacovec Cavern. We show that these previously dated flowstones are stratigraphically invasive within Member 4 and that they therefore undervalue the real age of the fossils.
The Sterkfontein cave fill including this and other Australopithecus fossils was dated to 3.4 to 3.6 million years ago, far older than formerly believed. The new date reverses the long-held concept that South African Australopithecus is a younger offshoot of East African Australopithecus afarensis.
The earth does not provide up its ancient secrets quickly– not even in the “Cradle of Humankind” in South Africa, where a wealth of fossils associating with human advancement have been found.
Scientists have studied these fossils of early human forefathers and their long-lost loved ones for years. Now, a dating approach established by a Purdue University geologist simply pushed the age of a few of these fossils discovered at the website of Sterkfontein Caves back more than a million years. This would make them even older than Dinkinesh, likewise called Lucy, the worlds most famous Australopithecus fossil.
Sterkfontein was made popular by the discovery in 1936 of the first adult Australopithecus, an ancient hominin. Given that then, hundreds of Australopithecus fossils have actually been found there, including the well-known Mrs. Ples, and the almost complete skeleton understood as Little Foot.
The Sterkfontein cave fill containing this and other Australopithecus fossils was dated to 3.4 to 3.6 million years ago, far older than formerly believed. Now, a dating method developed by a Purdue University geologist simply pressed the age of some of these fossils discovered at the website of Sterkfontein Caves back more than a million years. People have actually looked at the animal fossils found near them and compared the ages of cave features like flowstones and gotten a variety of various dates. Given that aluminum-26 is formed when a rock is exposed at the surface area, but not after it has actually been deeply buried in a cave, PRIME lab scientists can date cave sediments (and the fossils within them) by determining levels of aluminum-26 in tandem with another cosmogenic nuclide, beryllium-10.
In addition to the brand-new dates at Sterkfontein based on cosmogenic nuclides, the research group made mindful maps of the cavern deposits and revealed how animal fossils of various ages would have been blended together during excavations in the 1930s and 1940s, leading to years of confusion with the previous ages.
