A new intensive survey of the Messak Settafet escarpment in southern Libya, a massive outcrop of sandstone in the middle of the Saharan desert, has shown that stone tools occur everywhere across the entire landscape, averaging 75 artefacts per square metre, in an area 350 kilometres long, and on average 60 kilometres wide - approximately 21,000 square kilometres.
     Researchers say this vast assemblage of stone-age tools were extracted from and discarded onto the escarpment over hundreds of thousands of years - 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 Dr Robert Foley, from the University of Cambridge, who conducted the research with colleague Dr Marta Mirazon Lahr.
     At the simple end, large flakes of stone would have been opportunistically hacked from boulders. At the more sophisticated level, researchers found evidence that specific tools had been used to wedge into the stone in order split it.
     Clusters of small quarrying pits dot the landscape, ranging up to 2 metres in diameter, and 50 centimetres in depth. These pits would have retained moisture, and the small pools would have attracted game. In many of these pits, the team found 'trapping stones': large stones used for traps and ties for game and cattle during the last 10,000 years.
     Although stone tool manufacture dates back at least 2.5 million years, the researchers limited their estimate to one million years. Based on their and others research, they standardised population density, tool volume, the number of tools used by one person in a year and the amount of resulting debris per tool. They estimate an average density of between 0.5 and 5 million stone artefacts per square kilometre of Africa.

Edited from Univeristy of Cambridge PR (11 March 2015), Mail Online (11 March 2015)