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., 1997). 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.
