An international team of researchers has discovered more than 30,000 artifacts at Panga ya Saidi, a cave in the humid coastal forest of Kenya, which is shedding new light on the crucial time period when Homo sapiens first started showing signs of modern behavior. The discovery is reported in the journal Nature Communications.
The Panga ya Saidi cave sequence dates back 78,000 years and is the only known site in East Africa with an unbroken archaeological record of human inhabitation.
“The new archeological cave site of Panga ya Saidi has a continuous record with people there right up until 500 years ago,” said co-lead author Dr. Ceri Shipton, from the Australian National University, the University of Cambridge and the British Institute in Eastern Africa.
“The site has amazing levels of preservation with so many of the artifacts in mint condition.”
“Previous sites relating to this early period of modern human behavior have all been in South Africa and the East African Rift Valley, this is the first site on the coast of East Africa and the first with such a continuous record.”
The analyses of archaeological plants, animals, and shells from the Panga ya Saidi site indicate a broad perseverance of forest and grassland environments.
As the cave environment underwent little variation over time, humans found the site attractive for occupation, even during periods of time when other parts of Africa would have been inhospitable. This suggests that humans exploited the cave environment and landscape over the long term, relying on plant and animal resources when the wider surrounding landscapes dried.
The ecological setting of Panga ya Saidi is consistent with increasing evidence that Homo sapiens could adapt to a variety of environments as they moved across Africa and Eurasia, suggesting that flexibility may be the hallmark of the species.
Homo sapiens developed a range of survival strategies to live in diverse habitats, including tropical forests, arid zones, coasts and the cold environments found at higher latitudes.
“It was highly unusual to find a site where early Homo sapiens were living in a tropical forest,” Dr. Shipton said.
“Early humans liked to be on open grassland where there is a lot of large animals for hunting. These people were living in tropical forest hunting smaller animals like monkeys and small deer, animals you may need more sophisticated technology to catch.”
“What is striking about this record is the innovations you see in technology and material culture, and the ability to exploit both forest and savannah environments. It is this kind of behavioral flexibility that allowed our species to populate the rest of the world outside of Africa.”
“Occupation in a tropical forest-grassland environment adds to our knowledge that our species lived in a variety of habitats in Africa,” said co-lead author Dr. Patrick Roberts, from the Max Planck Institute for the Science of Human History.
“The East African coastal hinterland and its forests and have been long considered to be marginal to human evolution so the discovery of Panga ya Saidi cave will certainly change archaeologists’ views and perceptions,” said co-lead author Nicole Boivin, also from the Max Planck Institute for the Science of Human History.
Of more than 30,000 items found at the site, some of the most remarkable include worked and incised bones, ostrich eggshell beads, marine shell beads, and worked ochre.
“Carefully prepared stone tool toolkits of the Middle Stone Age occur in deposits dating back to 78,000 years ago, but a distinct shift in technology to the Later Stone Age is shown by the recovery of small artifacts beginning at 67,000 years ago. The miniaturization of stone tools may reflect changes in hunting practices and behaviors,” the researchers said.
“The Panga ya Saidi sequence after 67,000, however, has a mix of technologies, and no radical break of behavior can be detected at any time, arguing against the cognitive or cultural ‘revolutions’ theorized by some archaeologists.”
“Moreover, no notable break in human occupation occurs during the Toba volcanic super-eruption of 74,000 years ago, supporting views that the so-called ‘volcanic winter’ did not lead to the near-extinction of human populations, though hints of increased occupation intensity from 60,000 years ago suggests that populations were increasing in size.”
The scientists also found the oldest known bead in Kenya, dating to 65,000 years ago.
“At about 33,000 years ago, beads were most commonly made of shells acquired from the coast,” they said. “While this demonstrates contact with the coast, there is no evidence for the regular exploitation of marine resources for subsistence purposes.”
“Ostrich eggshell beads become more common after 25,000 years ago, and after 10,000 years ago, there is again a shift to coastal shell use.”
“In the layers dating to between 48,000 to 25,000 years ago, carved bone, carved tusk, a decorated bone tube, a small bone point, and modified pieces of ochre were found.”
“Though indicative of behavioral complexity and symbolism, their intermittent appearance in the cave sequence argues against a model for a behavioral or cognitive revolution at any specific point in time.”
Ceri Shipton et al. 2018. 78,000-year-old record of Middle and Later stone age innovation in an East African tropical forest. Nature Communications 9, article number: 1832; doi: 10.1038/s41467-018-04057-3