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 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 artifacts 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 years ago, 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 suggest 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 and 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 stated:
“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 added:
“Occupation in a tropical forest-grassland environment adds to our knowledge that our species lived in a variety of habitats in Africa.”
Professor Michael Petraglia said:
“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.”
Provided by: University of Chicago Medicine [Note: Materials may be edited for content and length.]
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