O’Connell, Ride of Second Horseman, pp. 57–58

J. L. Angel, ‘Paleoecology, Pleodeography and Health’, in S. Polgar, ed., Population, Ecology and Social Evolution (The Hague, 1975); David Rindos, The Origins of Agriculture: An Evolutionary Perspective (Orlando, Fla., 1984), pp. 186–87