Corruccini et al. apply our method of fertility estimation to a Barbados slave population, find that it yields contradictory and erratic estimates of the crude birth rate (CBR), examine its theoretical basis, and conclude that a pessimistic view of paleodemography in general is warranted. We argue that the sample utilized by Corruccini et al. is not well suited for methodological testing. Misestimates of fertility more likely were caused by the peculiarities of this particular sample than by flaws in our method or weaknesses in its theoretical foundation. Deterministic simulations also demonstrate that our method is theoretically well founded. We cannot, therefore, share Corruccini et al.'s pessimism concerning the feasibility of paleodemographic research.
Holland suggests we have erred by providing a "unicausal" model for increased fertility in prehistoric west-central Illinois. He argues that a fuller multicausal model including coevolutionary effects provides a more accurate depiction of the prehistoric events contributing to increased fertility. We appreciate Holland's call for more elaborate models of prehistoric behaviors and evolutionary interactions between humans and other organisms. Unfortunately, his model is untestable because it includes a feedback loop with no exogenous variables. Because of a lack of outside input, Holland's model is immobile and cannot be used in itself to explain changes in organismal biology or behavior.