London: A new intensive survey of the Messak Settafet escarpment, a massive outcrop of sandstone in the middle of the Saharan desert, has shown that stone tools occur "ubiquitously" across the entire landscape - averaging 75 million artefacts per square kilometre.
Researchers say the vast 'carpet' of stone-age tools -- extracted from and discarded onto the escarpment over hundreds of thousands of years -- is the earliest known example of an entire landscape being modified by hominins -- the group of creatures that include us and our ancestral species.
"The Messak sandstone, now in the middle of the vast sand seas of Libya, would have been a high quality rock for hominins to fracture.
"The landscape is in effect a carpet of stone tools, most probably made in the Middle and Upper Pleistocene," said lead researcher Robert Foley from University of Cambridge.
The Messak Settafet runs a total length of 350 km, with an average width of 60 km.
Parts of the landscape are 'anthropogenic', or man-made, through build-up of tools over hundreds of thousands of years.
The research team have used this and other studies to attempt to estimate the volume of stone tools discarded over the last one million years of human evolution on the African continent alone.
They say that it is the equivalent of more than one Great Pyramid of Giza per square kilometre of the entire continent.
"The term 'anthropocene' is now used to denote the point at which humans began to have a significant effect on the environment," said co-researcher Marta Mirazan Lahr.
"The Messak Settafet is the earliest demonstrated example of the scars of human activity across an entire landscape ... the effects of our technology on the environment may be considerably older than previously thought," Mirazan Lahr added.
The study was published in the journal PLOS ONE.