ERRATUM. In the original published version of the Literature Cited section, the spelling for sustainability in the citation to Tainter et al. 2001 was erroneous:

Tainter, J., T. F. H. Allen, and T. W. Hoekstra. 2001. Sustainabily and resource transitions.

The correct citation is as follows:

Tainter, J., T. F. H. Allen, and T. W. Hoekstra. 2001. Sustainability and resource transitions.

April 3, 2003