Theory Building with System Dynamics: Ice Age Extinctions

摘要

A recently developed system dynamics model specifies a new hypothesis for the extinctions at the end of the Pleistocene – Second Order Predation – and compares it with the overkill hypothesis (see http://quaternary.net/extinct2000). It provides a quantitative description of the interrelationships between four plant stocks, four herbivore stocks, carnivores, and H. sapiens. Different assumptions regarding H. sapiens in-migration, hunting of prey or predators, can be simulated. Second Order Predation: i.e. H. Sapiens killing of other carnivores, leads to herbivore overpopulation, environmental degradation, and differential extinction of herbivores. The paper suggests thinking about whole system evolution and calls for additional models that will support comparison of competing hypotheses, allow precision in quantities and timing, and exhibit internal dynamics. It challenges scientists conversant with models to simplify models to encourage their use by their colleagues.