Levinton notes that the number of individuals available to my study of patterns in the evolution of Homo erectus is low, especially when cranial base breadth is considered. If measurements of biauricular breadth are related to stratigraphic age of the fossils using linear regression, the slope obtained is small (−1.52). The confidence interval includes zero, and there is no evidence that a real trend is present. At the same time, the .95 interval is large (±26.81), so slopes differing by even a substantial margin cannot be distinguished. Levinton suggests that this negates a claim for stasis, and I agree that there are grounds for doubt. But by his reasoning, a case for stasis can never be established. While it is true that the occurrence of (very small) trends can never be denied, even if an analysis of many fossils shows a zero slope bracketed by narrow confidence limits, surely these “trends” must be dismissed as insignificant. Given such an outcome, a conclusion of no (directional) change would be quite justified.

The degree to which the relative abundances of the species in a fossil assemblage represent those in the living community from which it came is an indication of the fidelity of the assemblage in preserving most of the aspects of community structure that we may hope to find in the fossil record. I have developed a model for the formation of attritional fossil mammal assemblages that shows that the logarithm of the number of individuals of each species in an ideal unbiased assemblage, when regressed on the logarithm of body mass, will exhibit a slope of approximately −1.05 ± 0.25 (approximate 95% confidence interval). This value is based upon ubiquitous scaling relationships of population density and turnover rate with body mass among extant mammals. These relationships are the results of widespread energetic and metabolic regularities in community structure and physiology and can be expected to have been essentially the same in the remote past. The slope of −1.05 provides for the first time a reference standard for community structure of sufficient generality for use in the analysis of this aspect of fossil assemblages. We can use this value as a sort of “null hypothesis” of no bias against which we can compare actual fossil assemblages.

Analysis of some promising assemblages reveals that they exhibit badly biased relative abundances. However, it is likely that in these cases we can explain this bias as almost entirely the result of pre-burial differential destruction of the carcasses of different-sized species.

The combination of this new, biological approach with the largely physical approaches of taphonomy and sedimentology will allow us to ask more specific questions about bias in fossil assemblages, avoiding circular arguments. We can now distinguish, in a large number of situations, assemblages that preserve reliable community-structure information from those that do not.

Diachronic variation in insectivore remains from a deeply stratified cave deposit in southeastern North America is described. The paleobotanical record for the region is congruent with variation in the soricid (shrew) and talpid (mole) faunal assemblages. Both faunal and floral records reflect considerable climatic change since the full Wisconsinan in this unglaciated portion of eastern North America. Variations in the insectivore assemblages indicate the presence of a more equable climate during the late Pleistocene. Continental climates ushered in at the end of the Pleistocene resulted in a marked decrease in insectivore diversity. Relative frequency changes in taxa throughout the Holocene reflect the mid-Holocene Climatic Optimum.