The Stone Age period may have continued 20,000 years longer in some part of Africa than was previously thought, recent archaeological finds revealed.
The new discoveries at sites in Senegal on the West coast of Africa, by Max Planck Institute researchers, are fuelling a rethink of the passage of human evolution.
Previous discoveries suggested humans in Africa stopped using certain kinds of tools and methods for making them in favour of 'miniaturised toolkits' around 30,000 years ago - marking the transition from Middle to Later Stone Age.
Archaeologists found ancient West African inhabitants were still using these tools about 11,000 years ago - up to 20,000 years after they went out of favour elsewhere.
This disproves a long-held theory that humanity evolved in one uniform way towards our modern lifestyle - and instead evolved at different speeds around the world.
Middle Stone Age finds most commonly occur in the African record between around 300 thousand and 30 thousand years ago, after which point they largely vanish.
Archaeologists say their research supports the idea that - for most of humanity's prehistory - groups of humans were relatively isolated from each other.
The discovery comes as archaeologists take some of the first steps in uncovering the prehistoric past of West Africa, which they say has been under-studied in comparison to the eastern and southern reaches of the continent.
The lead author of a new study, Dr Eleanor Scerri, said West Africa is a real frontier for human evolutionary studies - as almost nothing is known about its prehistory.
'Almost everything we know about human origins is extrapolated from discoveries in small parts of eastern and southern Africa,' explained Scerri.
Her colleague, Dr Khady Niang, of the University of Cheikh Anta Diop in Senegal, added: '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.
'Prior to our work, the story from the rest of Africa suggested that well before 11,000 years ago, the last traces of the Middle Stone Age were long gone.'
The team don't know exactly why West Africa's Stone Age inhabitants took longer to adopt new tools, but speculate it could be because of geographical isolation.
Other theories suggest it could also be due to less radical changes in climate which meant humans living there didn't need to find new ways to adapt.
Dr Niang said: '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.'
Axe with intact shaft uncovered at Rødbyhavn, Denmark. Dates to the Stone Age, about 5,500 years ago pic.twitter.com/oCT2BnrKd3— Museum Archive (@ArtifactsHub) January 11, 2021
The team said their findings, along with genetic discoveries which show a huge amount of diversity among humans living on the continent, fit with a newer view of human evolution that Stone Age groups lived and developed separately.
Dr Niang said: '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.'
Around 15,000 years ago, a major increase in humidity and forest growth in central and western Africa linked different areas and provided corridors for groups to disperse - spelling the end for Middle Stone Age tools.
Dr Scerri added: 'These findings do not fit a simple unilinear model of cultural change towards 'modernity'.
'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 findings were published in the journal Scientific Reports.
This article has been adapted from its original source.
© Associated Newspapers Ltd.