article_snippet: 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.
article_snippet: The researchers found an average of 75 man-made tools in each square metre
article_snippet: By combining combining their data with previous extensive surveys carried out across Africa 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.
article_snippet: The researchers estimated that there could be an average of between 0.5 and 5 million stone artefacts per square kilometre across Africa.
highlights_snippet: Archaeologists at the University of Cambridge discovered an average of 75 tools in every square meter of ground .
  
highlights_snippet: Pits and holes left by quarrying of stone estimate that early human ancestors could have left behind up to five million stone tools in every square kilometre of Africa .