Figure 3.

The relationship between time and the directly observed rate of abandonment of rockshelter occupations: the rate of abandonment appears to increase towards the present, presumably because of loss of evidence from long-abandoned sites. Data are from a total of 142 rockshelters from six regions (see text for locations and references). The fit (with 95% confidence limits) is from a logistic regression, weighted by sample size. Sample size increases from 15 in the earliest interval to 118 sites in the most recent. The outlier to the right of the curve has only a small influence on the regression, being due to a single abandonment in a sample of 15 rockshelters dated to that interval.