Dating the Cradle

New research published today in Nature by an international research team – including scientists from the Department of Archeology and History of the University of La Trobe and the School of Earth Sciences at the University of Melbourne – are the first to provide a comprehensive schedule of early human evolution as part of the cradle of humanity in southern Africa.

The research conducted by the University of Cape Town also sheds light on the climatic conditions of our earliest ancestors in the area.

Until now, the lack of dating methods for cradle fossils made it difficult for scientists to understand the relationship between species of hominins from East and South Africa. What's more, South African records were often considered unadjusted compared to East Africa, where the layers of volcanic ash allow for high-resolution dating.

Professor Andy Herries, who conducted research and excavations in many places with a date, noted that "although the South African record was the first to show Africa as a starting point for humans, the complexity of the caves and the difficulty of their dating made the South African record difficult to interpreting. "

"In this study, we show that the stones in the caves can act almost like volcanic layers of East Africa, forming in different caves at the same time, which allows us to directly relate their sequences and fossils to regional sequences," said Professor Herries.

Professor Jon Woodhead from the University of Melbourne said research results show that

"Cradle caves are only dating to six specific time periods from about 3.2 to 1.3 million years ago."

Chief scientist from the University of Cape Town, Dr. Robyn Pickering, said: "Unlike previous dates, which often focus on one cave, sometimes even only one cave chamber, we provide a direct age of eight caves and a model to explain the age of all fossils from all over region.

"Now we can combine the discoveries from separate caves and create a better picture of the evolutionary history in Southern Africa."

The cradle of humanity is a place of world heritage built of complex fossil caves. It is the richest place in the world of early hominine and home to almost 40 percent of all known human ancestors of the fossils, including the famous africanopithecus africanus skull called Mrs Ples.

Using a state-of-the-art uranium lead-based dataset developed at the University of Melbourne, the researchers analyzed 28 layers of stone that were found sandwiched between fossil-rich sediments in eight caves throughout the cradle. The results revealed that the fossils in these caves date back to six narrow time windows from 3.2 to 1.3 million years ago.

"Stones are the key," said Dr. Pickering.

"We know that significant stones rise only in caves during wet periods, when there is more rain outside the caves." By dating the stones, we choose the time of increased rainfall, so we know that in between the times when the caves were open, the climate was more dry and more like to what we are currently experiencing. "

This means that early hominins living in the cradle have experienced major changes in the local climate, from humid to drier, at least six times between 3 and a million years ago. However, human fossils are preserved only during the drying periods preserved in caves, distorting the record of early human evolution.

This new job, financed in part by Dr. Pickering and prof. Herry & # 39; ego "ARC DECRA" and "Future scholarships", is the fruit of over a decade of work and brings together a team of 10 scientists from Australia, South Africa and the United States. Most of the dating analysis was conducted at the University of Melbourne, which remains the world leader in this type of dating analysis. These results bring Cradle to the forefront and open up new opportunities for scientists who answer complex questions about the history of mankind in the region.

"Robyn and her team have greatly contributed to our understanding of human evolution," said the leading paleoanthropologist prof. Bernard Wood from the Center for Advanced Studies in Human Paleobiology at the George & # 39; University of Washington in the USA, who is not the author of the study.

"This is the most important progress to be made since the fossils have been discovered." The fossil record dates are of great importance, and the value of South African evidence has been increased many times by this exemplary study of its temporal and depositive context. "