He reports some recent research on the disappearance of the Anasazi culture in
the Southwest.
Interesting speculation from the standpoint of cultural selection and
competition among rival religions.
New evidence suggests that the exodus was not due so much to drought as to a
shift in seasonal rainfall patterns -- so that the traditional rain-producing
rituals were seen to have lost their power. When the Anasazi peoples
dispersed and relocated, they no longer built kivas (so abandoning the
hierarchical "kiva culture"). Instead they took up with a number of
different secret societies, including the Kachina cult from the south (which
was more open and egalitarian).
It struck me that there are very few examples where a "failure of faith" led
to the extinction of a culture's religion. The religious meme seems, by
design, to be protected from such easy discomfirmation. Which may make the
Anasazi theory a little dubious.