The pattern of evolution in Pleistocene human brain size

With a sample of 94 Pleistocene cranial capacities between the time period of 1.8 Ma and 50 Ka now known, we consider the evolution of cranial capacity in Homo, with the null hypothesis that the changes over time are a result of one process. We employ a new method that uses a resam- pling approach to address the limitations imposed on the methods of previous studies. To test the null hypothesis, we examine the distribution of changes in adjacent temporal samples and ask whether there are differences between earlier and later samples. Our analyses do not reject the hypothesis of a single process of brain size change, but they are incompatible with an interpretation of punctuated equilibrium during this period. The results of this paper are difficult to reconcile with the case for cladogenesis in the Homo lineage during the Pleistocene.