A major cave site, which records substantial activities of hunter-gatherers, and later Iron Age communities, was excavated by an international interdisciplinary group of scholars working along the East African coast in Kenya.
The study, which was published in Nature Communications today, revealed that humans lived in the humid coastal forest and were able to make technological innovations 67,000 years ago, showing gradual changes in cultural, technological, and symbolic advancements.
The detailed environmental study revealed that human occupations occurred 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.
The deep archaeological sequencing of Panga ya Saidi cave helped produce 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 beads in Kenya, dating to more than 65,000 years ago.
The research study revealed that ostrich eggshell beads became more common 25,000 years ago, and 10,000 years ago, there was 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 behavioural complexity and symbolism, their sporadic appearance in the cave sequence argues against a model for a behavioural or cognitive revolution at any specific point in time.
Before the mentioned discovery, little information was available about the last 78,000 years in coastal East Africa, with the majority of archaeological research focused on the Rift Valley in South Africa. The study depended on scientific analyses of archaeological plants, animals, and shells from the cave to indicate a broad perseverance of forest and grassland environments.
As the cave environment was exposed to little variation over time, humans found the site attractive for occupation, even during periods of time when other parts of Africa would have been very hard for life, according to the paper.
Findings of the study suggest 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 in Kenya 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 major characteristic of our species.
The research shows that Homo sapiens developed a range of survival strategies to live in diverse habitats, including tropical forests, arid zones, coasts, and cold environments found at higher latitudes.
While the carefully prepared stone tools and toolkits of the Middle Stone Age were found in deposits dating back to 78,000 years ago, 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 researchers of the study believe that the miniaturisation of stone tools may reflect changes in hunting practices and behaviours. The Panga ya Saidi sequence at 67,000 years ago, however, has a mix of technologies, and no radical break of behaviour can be detected at any time, arguing against the cognitive or cultural revolutions theorised by some archaeologists.
Scientists found that no notable break in human occupation occurred 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 signs of increased occupation intensity from 60,000 years ago suggests that populations were increasing in size.
The research revealed that 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.
Research leader and director of the Department of Archaeology at the Max Planck Institute for the Science of Human History, Nicole Boivin, said, “the East African coastal hinterland and its forests 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.”
Co-author and leader at the Max Planck’s Department of Archaeology’s new stable isotope research group, Patrick Roberts, added that, “occupation in a tropical forest-grassland environment adds to our knowledge that our species lived in a variety of habitats in Africa.”
Michael Petraglia, who took part in the study, further explained, “the finds at Panga ya Saidi undermine hypotheses about the use of coasts as a kind of super highway that channelled migrating humans out of Africa, and around the Indian Ocean rim.”