section_path: Consequences/Subsequent revolutions
section_name: Subsequent revolutions
paragraph_text: Subsequent revolutions
  
  Andrew Sherratt has argued that following upon the Neolithic Revolution was a second phase of discovery that he refers to as the secondary products revolution. Animals, it appears, were first domesticated purely as a source of meat. The Secondary Products Revolution occurred when it was recognised that animals also provided a number of other useful products. These included:
  
  Sherratt argued that this phase in agricultural development enabled humans to make use of the energy possibilities of their animals in new ways, and permitted permanent intensive subsistence farming and crop production, and the opening up of heavier soils for farming. It also made possible nomadic pastoralism in semi arid areas, along the margins of deserts, and eventually led to the domestication of both the dromedary and Bactrian camel. Overgrazing of these areas, particularly by herds of goats, greatly extended the areal extent of deserts.