Discarded stone tools made by early humans have formed a vast 'carpet' in part of the Sahara desert in what scientists say could be the first man-made landscape. Archaeologists working in southern Libya have found that large sections of a 350km (217 miles) long escarpment has been built up from dropped stone tools. They discovered as many as 75 tools in just a single square metre of ground along the slopes of Massak Settafet, near Fezzan, Libya. Scroll down for video . The Massak Settafet escarpment (above) near Fezzan Libya could be the world's first man-made landscape . And they have estimated that there could be between 500,000 and five million tools created by early humans for every square kilometre of Africa. This is the equivalent amount of rock as that used to build the Great Pyramid of Giza in Egypt. It is hard for scientists to say precisely when humans started making tools because the more primitive remains look like a natural object rather than a human artefact. The oldest-known instruments are the Oldowan stone tools from Ethiopia, which date back about 2.6 million years. The Acheulean tool technology period - up to 1.76 million years ago - featured large stone hand axes made from flint and quartzite. Towards the end of this period, the tools became more refined and then followed the so-called Levallois technique, which saw the creation of scrapers, slicers, needled and flattened needles. About 50,000 years ago more refined and specialised flint tools were made and used by Neanderthals and it is believed it was at this stage tools were constructed out of bone. As human culture advanced, artefacts such as fish hooks, buttons and bone needles were used. Cut marks have found on animal bones that have been dated to be 3.4 million years old - around the time that a squat ape-like ancestor called Australopithecus afarensis - known as Lucy - roamed Africa. The researchers behind the study claim their findings may force a rethink on how we define human history and the impact we have had on the environment. Dr Marta Mirazón Lahr, a reader in human evolution at the University of Cambridge, said: 'The term 'anthropocene' is now used to denote the point at which humans began to have a significant effect on the environment. 'The critical time may well be the beginning of the industrial revolution about 200 years ago. 'Some talk of an 'early anthropocene' about 10,000 years ago when forests began being cleared for agriculture. 'Making stone tools, however, dates back more than two million years, and little research has been done on the impact of this activity. '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.' The researchers, whose work is published in the journal Public Library of Science One conducted a survey of the site in the Sahara in 2011 by randomly examining plots along the plateau of the Massak Settafet enscarpment. They sifted through the sandstone rocks in each plot searching for those that showed signs that they had been worked by humans. One of the key pieces of evidence for human tool making is a characteristic bulge or dent on the surface of a stone known as a bulb of percussion. This is created by the angular blow from a human as they attempted to knock flakes off larger pieces of rock. The researchers estimate there are millions of stone tools like the one above littering the landscape in Libya . The stone tools were discovered along a 217 mile long escarpment in Messak Settafet in southern Libya . The researchers found an average of 75 man-made tools in each square metre they looked in - ranging from large flakes knocked off boulders that were used for cutting to sophisticated stone shapes. They found evidence that specific tools had been used to wedge into pieces of stone to help slit it in certain ways. Dr Robert Foley, from the Leverhulme Centre for Evolutionary Studies at the University of Cambridge who also took part in the study, said: '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 Messak Settafet runs for 350km (217 miles) and much of it appears to have been shaped by human hands . 'The landscape is in effect a carpet of stone tools, most probably made in the Middle and Upper Pleistocene. 'It is clear from the scale of activity how important stone tools were, and shows that African hominins were strongly technologically dependent. 'Landscapes such as these must have been magnets for hominin populations, either for "stone foraging trips" or residential occupation.' The researchers say that the intensive stone tool industry in the Messak Settafet also shaped the landscape in a way that helped later human inhabitants. The landscape is dotted with small quarrying pits where stone was bashed out from larger boulders to leave holes around two metres wide and half a metre deep. Scientists looked for bulges or dents on the surface of stones, like above, for signs of human modification . The rocks above appear to have been broken off a larger boulder or had chunks bashed off them by humans . These pits would have helped to trap water, which would have attracted game. In many of these pits the scientists found 'trapping stones' - large rocks used for traps and ties for game or cattle over the past 10,000 years. By combining their data with previous extensive surveys carried out across Africa, the researchers also attempted to estimate roughly how much stone had been used as tools and discarded during human evolution. Although stone tool manufacture dates back at least 2.5 million years, the researchers limited the estimate to one million years. They estimated that there could be an average of between 0.5 and 5 million stone artefacts per square kilometre across Africa. The research team from the University of Cambridge studied the rocks in metre square plots on the groun .
Archaeologists at the University of Cambridge found huge numbers of stone tools on the ground in Massak Settafet near Fezzan in southern Libya . They discovered an average of 75 tools in every square meter of ground . Tools are thought to have been made 500,000 years ago in the Pleistocene . Scientists say it could be the earliest example of a man-made landscape . Pits and holes left by quarrying of stone helped attract animals to the area . The researchers estimate that early human ancestors could have left behind up to five million stone tools in every square kilometre of Africa .