The ancient human culture of the Middle Stone Age persisted 20,000 years longer than previously thought, according to a team of researchers led by the Max Planck Institute for the Science of Human History. The study reveals that tool-making traditions of the Middle Stone Age, which were believed to have vanished from the African record 30,000 years ago, were still used in parts of West Africa up until just 11,000 years ago.
Tools known as “scrapers” and “points” were assumed to have been completely replaced by a miniaturized toolkit that was better suited for mobile groups of hunter-gatherers. However, evidence of Middle Stone tools found at sites throughout modern-day Senegal show they were being used 20,000 years later than what was expected.
“West Africa is a real frontier for human evolutionary studies – we know almost nothing about what happened here in deep prehistory. Almost everything we know about human origins is extrapolated from discoveries in small parts of eastern and southern Africa,” said study lead author Dr. Eleanor Scerri.
To investigate, Dr. Scerri collaborated with Dr. Khady Niang of the University of Cheikh Anta Diop to organize a research expedition to different regions of Senegal. Across stretches of two major river systems, the Senegal and the Gambia, the team found multiple Middle Stone Age sites that all had surprisingly young dates.
“These discoveries demonstrate the importance of investigating the whole of the African continent, if we are to really get a handle on the deep human past.” said Dr. Niang. “Prior to our work, the story from the rest of Africa suggested that well before 11 thousand years ago, the last traces of the Middle Stone Age – and the lifeways it reflects – were long gone.”
It is not yet clear why this region of West Africa was home to such a late persistence of Middle Stone Age culture.
“To the north, the region meets the Sahara Desert,” explained study co-author Dr. Jimbob Blinkhorn. “To the east, there are the Central African rainforests, which were often cut off from the West African rainforests during periods of drought and fragmentation. Even the river systems in West Africa form a self-contained and isolated group.”
“It is also possible that this region of Africa was less affected by the extremes of repeated cycles of climate change,” added Dr. Scerri. “If this was the case, the relative isolation and habitat stability may simply have resulted in little need for radical changes in subsistence, as reflected in the successful use of these traditional toolkits.”
“All we can be sure about is that this persistence is not simply about a lack of capacity to invest in the development of new technologies. These people were intelligent, they knew how to select good stone for their tool making and exploit the landscape they lived in,” said Dr. Niang.
The research supports the idea that for most of humanity’s deep prehistory, populations were relatively isolated from each other and lived in subdivided groups in different regions.
For a short time, Middle Stone Age populations lived alongside other groups that were already using the more recently developed miniaturized toolkits in a culture that is referred to as the “Later Stone Age.”
“This matches genetic studies suggesting that African people living in the last ten thousand years lived in very subdivided populations,” said Dr. Niang. “We aren’t sure why, but apart from physical distance, it may be the case that some cultural boundaries also existed. Perhaps the populations using these different material cultures also lived in slightly different ecological niches.”
About 15,000 years ago, there was a major increase in humidity and forest growth in western Africa that could have linked different areas and provided new passageways for genetic and cultural mixing. According to the researchers, this was likely the beginning of the end of humanity’s first and earliest culture.
“These findings do not fit a simple unilinear model of cultural change towards ‘modernity’,” explained Dr. Scerri. “Groups of hunter-gatherers embedded in radically different technological traditions occupied neighbouring regions of Africa for thousands of years, and sometimes shared the same regions. Long isolated regions, on the other hand, may have been important reservoirs of cultural and genetic diversity. This may have been a defining factor in the success of our species.”
The study is published in the journal Scientific Reports.
By Chrissy Sexton, Earth.com Staff Writer