Kenyan cave sheds new light on dawn of modern man
Archaeologists have discovered more than 30,000 items at the site which is shedding new light on the crucial time period when Homo sapiens first started showing signs of modern behaviour.
The research was led by archaeologist Dr Ceri Shipton of The Australian National University (ANU) School of Culture, History and Language, who said 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.
"It is the most beautiful site I have ever worked on. As soon as I saw it I knew it was special," Dr Shipton said.
"It has a continuous record with people there right up until 500 years ago.
"The site has amazing levels of preservation with so many of the artefacts in mint condition."
Dr Shipton said the site, on the Kenyan south coast just north of Mombasa, was providing new insights into the Later Stone Age - a period of time beginning about 67,000 years ago associated with the rise of modern human behaviour and culture in Africa.
"You start to see things like decorated bones, beads made from marine shell or ostrich eggs, miniaturized stone tools, and bones carved into things like arrow points. This is the oldest date we have for when this behaviour is first observed," he said.
"Previous sites relating to this early period of modern human behaviour 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."
Dr Shipton said it was highly unusual to find a site where early Homo sapiens were living in a tropical forest.
"Early humans liked to be on open grassland where there is a lot of large animals for hunting," Dr Shipton said.
"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 behavioural flexibility that allowed our species to populate the rest of the world outside of Africa."
Professor Andy Herries from La Trobe University Archaeology undertook archaeomagnetic analysis of the cave sediments which showed that the transition in stone tool technology took place during a particularly cold and dry glacial period.
"the site documents the earliest evidence of this style of microlithic Later Stone Age technology and shows how early modern humans were able to adapt to a range of new environments at this time," Professor Herries said.
"It is a small precursor to our eventual habitation of every corner and environment on the planet."
Of more than 30,000 items found at the site, some of the most remarkable include 48,000 year old red ochre crayons and engraved bones. Dr Shipton was struck by the high-level preservation of the artefacts.
"The stone tools are still sharp. The beads and engraved bones have survived intact which is really rare," he said.
"On the crayons we can still see the grooves where they have been used. They're in the same condition now as when people discarded them."
The study was published on Wednesday in the Nature Communications journal. The project was led by the Max Planck Institute for the Science of Human History.
An international, interdisciplinary group of scholars working along the East African coast have discovered a major cave site which records substantial activities of hunter-gatherers and later, Iron Age communities. Detailed environmental research has demonstrated that human occupations occur in a persistent tropical forest-grassland ecotone, adding new information about the habitats exploited by our species, and indicating that populations sought refuge in a relatively stable environment. Prior to this cave excavation, little information was available about the last 78,000 years from coastal East Africa, with the majority of archaeological research focused on the Rift Valley and in South Africa.
Humans lived in the humid coastal forest
A large-scale interdisciplinary study, including scientific analyses of archaeological plants, animals and shells from the cave indicates 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 our 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.
Technological innovations occur at 67,000 years ago
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 artefacts beginning at 67,000 years ago. The miniaturization of stone tools may reflect changes in hunting practices and behaviors. 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.
Earliest symbolic and cultural items found at Panga ya Saidi cave
The deep archaeological sequence of Panga ya Saidi cave has produced a remarkable new cultural record indicative of cultural complexity over the long term. Among the recovered items are worked and incised bones, ostrich eggshell beads, marine shell beads, and worked ochre. Panga ya Saidi has produced the oldest 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. 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.
Project Principal Investigator and Director of the Department of Archaeology at the Max Planck Institute for the Science of Human History Dr. Nicole Boivin states, "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."
Group Leader of the Stable Isotopes Lab Dr. Patrick Roberts adds, "Occupation in a tropical forest-grassland environment adds to our knowledge that our species lived in a variety of habitats in Africa."
"The finds at Panga ya Saidi undermine hypotheses about the use of coasts as a kind of 'superhighway' that channeled migrating humans out of Africa, and around the Indian Ocean rim," observes Professor Michael Petraglia.