Artificial Life VI

A Classification of Long-Term Evolutionary Dynamics

Mark A. Bedau
Reed College

Emile Snyder
Reed College

Norman H. Packard
Prediction Company


We present empirical evidence that long-term evolutionary dynamics fall into three distinct classes, depending on whether adaptive evolutionary activity is absent (class 1), bounded (class 2), or unbounded (class 3). These classes are defined using three statistics: diversity, new evolutionary activity (Bedau & Packard 1992), and mean cumulative evolutionary activity (Bedau et al.1996). The three classes partition all the long-term evolutionary dynamics observed in Holland's Echo model (Holland 1992), in a random-selection adaptively-neutral "shadow" of Echo, and in the biosphere as reflected in the Phanerozoic fossil record. This classification provides quantitative evidence that Echo lacks the unbounded growth in adaptive evolutionary activity observed in the fossil record.

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